Mechanical and chemical surface treatment of golf club heads

Abstract

Described herein is a method for treating a metallic golf club head in a series of post-assembly steps to provide a hardened dark coating. The methods described herein include a quench-polish-quench (QPQ) process that yields a surface coating having improved hardness, uniformity, and porosity characteristics, thereby reducing visible surface deformation and durability loss.

Description

[0001] Cross-Reference to Priority

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 383,234, filed on Nov. 10, 2022, the content of which is incorporated herein by reference in its entirety. Field of the Disclosure

[0003] The present disclosure generally relates to golf club heads and methods for heat treating the outer surface of a golf club head to increase the surface hardness and corrosion resistance of the outer surface of the golf club head. The methods described herein may relate to golf equipment and, more specifically, to materials for the face and the golf club body, as well as methods of manufacturing and heat treating.

[0004] Background

[0005] Golf club heads can be manipulated to change the physical and mechanical properties of the club head. Golf club heads undergo several manufacturing processes to obtain a final product with desired physical specifications. For example, after manufacturing a golf club head by casting or forging, various surface treatments can be applied to obtain desired mechanical and physical properties. After the surface treatment, the loft angle and / or the lie angle of the golf club head can be manipulated.

[0006] Both the loft angle and the lie angle directly affect the ability of the golf club head to accurately direct a golf ball to a desired target line at a desired launch angle. The loft angle of a golf club head (also referred to as “loft”) is the angle formed between the club face and the ground plane when the golf club is held in the ready-to-strike position. The loft affects the trajectory and the spin rate of the golf ball. The lie angle of a golf club head (also referred to as “lie”) is the angle formed between the shaft and the ground plane when the golf club is held in the ready-to-strike position. Without the proper lie angle, a player will lose the ability to consistently and accurately advance a golf ball along a desired target line at a desired launch angle. Therefore, it is necessary to adjust the loft angle and the lie angle after the club head is formed to ensure that the desired loft angle and lie angle are achieved.

[0007] During such bending operations, the club head may exhibit cosmetic defects such as stress marks and / or structural failures. More specifically, tension may cause cracks to form on the outer surface of the club head. Conventional surface treatment methods, such as the known quench-polish-quench process, result in harnesses and material structures that are prone to surface cracking during bending or other physical operations during manufacturing. Accordingly, there is a need in the art for a manufacturing process that provides the desired surface hardness of a golf club head while minimizing the presence of surface cracks on the hosel. Brief Description of the Drawings

[0009] To facilitate further description of the embodiments, the following drawings are provided, in which:

[0010] Figure 1 FIG. illustrates a block diagram of a process for performing a quench-polish-quench heat treatment.

[0011] Figure 2 FIG. illustrates a chemical formula depicting a chemical reaction.

[0012] Figure 3 FIG. illustrates a chemical formula depicting a chemical reaction.

[0013] Figure 4 FIG. illustrates a front view of a golf club head.

[0014] Figure 5A is an image showing the exterior of the hosel of a golf club head having a surface treatment area.

[0015] Figure 5B is a view showing Figure 5A a focused view of the exterior of the hosel area of a golf club head.

[0016] Figure 5C is a view showing a Figure 5A cross-sectional enlarged view of the hosel area of a golf club head including surface cracks.

[0017] Figure 5D is a view showing Figure 5A a further enlarged cross-sectional view of the hosel area of a golf club head, depicting a nitride layer and a core.

[0018] Figure 5E is a view showing Figure 5A an even further enlarged cross-sectional view of the hosel area of a golf club head, depicting a core, a nitride layer, and a first oxide layer and a second oxide layer.

[0019] Figure 5F is a view showingFigure 5A An image of an enlarged side view of a surface crack in the hosel region of a golf club head.

[0020] Figure 5G Shows Figure 5A An image of an enlarged side view of a cross-section of the core of the hosel region of a golf club head.

[0021] Figure 6A An image of the exterior of the hosel of a golf club head having a surface treatment region.

[0022] Figure 6B Shows Figure 6A An image of a focused view of the exterior of the hosel region of a golf club head.

[0023] Figure 6C Shows a cross-sectional enlarged view of the hosel region of a golf club head including a surface crack Figure 6A An image of the cross-sectional enlarged view of the hosel region of a golf club head.

[0024] Figure 6D Shows Figure 6A An image of a further enlarged view of the cross-section of the hosel region of a golf club head, depicting a nitride layer and a core.

[0025] Figure 6E Shows Figure 6A An image of an even further enlarged view of the cross-section of the hosel region of a golf club head, depicting a core, a nitride layer, and a first oxide layer and a second oxide layer.

[0026] For simplicity and clarity of illustration, the drawings show the general manner of construction and may omit descriptions and details of well-known features and techniques to avoid unnecessarily obscuring the invention. Additionally, the elements in the drawings are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be exaggerated relative to other elements to help improve understanding of the embodiments of the invention. Like reference numerals in different figures represent the same elements.

[0027] This document describes a golf club head that includes a uniform nitride layer and an oxide layer. The formation of a flat and uniform nitride layer in actual metal bonding of the golf club head significantly improves the bonding with the oxide layer and helps to form an oxide layer with a more uniform thickness. The improved bonding and uniformity reduce the porosity caused by the agitation of the applied oxide layer. Although some porosity associated with porosity grades 1-3 near the surface is expected and considered acceptable, porosity deeper below the surface is not desirable and is mitigated by the QPQ method described herein. Specifically, porosity associated with porosity grades 4-5 below the surface and visible in conventional QPQ methods prompts cracks that are highly visible to the user and reduces the stability of the material, thereby increasing the risk of deformation or failure. Therefore, the uniformity of the layer results in a porosity grade of 3 or better, which limits the formation and growth of cracks, leading to fewer cracks that are smaller and thus less visible to the user. These uniform layers can be achieved by an improved quench-polish-quench method, as discussed in detail below.

[0028] Definitions

[0029] As used herein, the terms "first," "second," "third," "fourth," etc. are used to distinguish between similar elements and do not necessarily describe a particular order or chronological sequence. It should be understood that the terms used are interchangeable under appropriate circumstances, such that the embodiments described herein, for example, can operate in an order other than the order illustrated or otherwise described herein. Additionally, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, such that a process, method, system, article, device, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, system, article, device, or apparatus.

[0030] As used herein, the terms "left," "right," "front," "rear," "top," "bottom," "upper," "lower," etc. are used for descriptive purposes and do not necessarily describe a permanent relative position. It should be understood that the terms so used are interchangeable under appropriate circumstances, such that the embodiments of the present invention described herein, for example, can operate in other directions than those illustrated or otherwise described herein.

[0031] As used herein, the terms "couple," "coupled," "couples," "coupling," etc. should be broadly understood and refer to electrically, mechanically, and / or otherwise connecting two or more elements or signals.

[0032] As used herein, the term "composition" is defined as the types and relative count of elements in a material. For alloy materials, the composition describes the weight percentage of each alloying element within the material.

[0033] As used herein, the term "tensile strength" is defined as the maximum strength that a material can absorb under a tensile or pulling load without failure. Here, failure occurs when fracture, breakage, or rupture happens.

[0034] As used herein, the term "brittleness" is defined as failure caused by sudden fracture without plastic deformation. Brittleness is further defined as the lack of ductility.

[0035] As used herein, "modulus of elasticity" or "Young's modulus" is the ratio of stress to strain and is the slope (E) of the stress - strain curve in the elastic region. The modulus is used to describe the stiffness of a material.

[0036] As used herein, the term "yield strength" or "proportional limit" is defined as the point on the stress - strain curve where a material is loaded in tension to the point of permanent or plastic deformation such that the deformation remains when the load has been removed.

[0037] As used herein, the term "elongation" or "minimum elongation" is a measure of the amount of stretch or elongation that a material can withstand before it begins to permanently deform.

[0038] As used herein, the term "quenching" is defined as the process of rapidly cooling a metal to obtain certain material properties. The rapid cooling can be achieved by applying a quenching medium at a predetermined temperature for a predetermined exposure time. The quenching medium can include caustic alkalis, oils, molten salts, and gases. The cooling rate and the quenching medium directly determine the mechanical properties of the metal after quenching.

[0039] As used herein, the term "quench - polish - quench" is defined as a thermochemical process in which nitrogen and carbon simultaneously diffuse into the surface of a material in the presence of a salt bath.

[0040] As used herein, the term "aging" is defined as a form heat treatment where the material is allowed to cool slowly to room temperature in order to increase strength.

[0041] As used herein, the term "pit furnace" defines a type of furnace used in metallurgical processes that typically requires lower temperatures. The pit furnace described herein can include a cylindrical shape and can also include an opening at the top of the furnace through which a holding fixture can be inserted. The pit furnace controls the atmosphere in which a golf club head is immersed. This can include, but is not limited to, controlling temperature and pressure.

[0042] As used herein, the term "metallurgical process" defines a process for extracting a metal into a purer form.

[0043] As used herein, the term "nitriding" is defined as a diffusion-related surface treatment having the ability to increase surface hardness. Nitriding can further enhance the following mechanical properties: wear resistance, minimized distortion, temper resistance, increased fatigue life, and reduced notch sensitivity.

[0044] As used herein, the term "compound layer" is defined as a coating formed on top of the surface of a material that is directly produced by the QPQ process. The compound layer can include multiple layers, including all applicable nitride layers and oxide layers formed by the QPQ process.

[0045] Before explaining any embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Further, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including", "comprising", "having" and their variants herein is intended to cover the items listed thereafter and their equivalents as well as additional items. All weight percentage (wt%) values described below are on a total weight basis.

[0046] General terms are provided herein for describing material properties associated with the disclosed materials. These definitions are considered industry standards and are provided by ASM International, a professional association of materials scientists and materials engineers.

[0047] As used herein, the term "geometric center point" or "geometric center" of the striking face can refer to the geometric center point of the strikeface perimeter and is at the midpoint of the face height of the striking face. In the same or other instances, the geometric center point can also be centered relative to an engineered impact zone, which can be defined by a grooved area on the striking face. As another method, the geometric center point of the striking face can be located according to the definition of a golf governing body such as the United States Golf Association (USGA).

[0048] As used herein, the term "ground plane" can refer to a reference plane associated with the surface on which a golf ball is placed. The ground plane can be a horizontal plane that is tangent to the bottom at the address position.

[0049] As used herein, the term "shaft plane" can refer to a reference plane that is tangent to the geometric center point of the striking face.

[0050] As used herein, the term "loft angle" may refer to the angle measured between the clubface plane and the XY plane (defined below).

[0051] As used herein, the term "face height" may refer to the distance measured parallel to the clubface plane between the top and bottom of the perimeter of the striking face.

[0052] As used herein, the term "lie angle" may refer to the angle between the hosel axis extending through the hosel and the ground plane. The lie angle is measured from a front view.

[0053] As used herein, the "geometric center height" of a fairway golf club head is the height measured perpendicular to the ground plane from the geometric center point of the golf club head.

[0054] As used herein, the "leading edge" of a club head may be identified as the lowest portion of the perimeter of the striking face.

[0055] Description

[0056] This document describes golf club heads and various methods for processing golf club heads in a series of post-manufacture steps to enhance the outer surface (hereinafter optionally referred to as the "outer surface") of a metal golf club head by providing a more uniform black coating or finish. The uniform finish greatly improves the bonding ability of the inner layers of the coating, as well as the uniformity, elasticity, and appearance. The improved bonding and uniformity prevent the formation of porosity caused by disturbances in the black finish. As mentioned above, while porosity near the surface is anticipated and considered acceptable, porosity beyond the region closest to the surface is undesirable because porosity beyond the surface results in undesirable deep cracks that are highly visible to the user and reduces the stability of the material, increasing the risk of deformation or failure. When the nitride layer, first oxide layer, and second oxide layer are non-uniform, these deep cracks extend down into the second oxide layer and the initial nitride layer. Thus, the uniformity of the finish can limit the formation and growth of cracks, thereby ensuring fewer cracks, which is valuable to the user. Such a uniform coating can be achieved by an improved quench-polish-quench (hereinafter referred to as "QPQ") method, as discussed in detail below.

[0057] The QPQ process can produce a more uniform surface hardness and improve the corrosion resistance of the outer surface by applying a QPQ finish to the golf club head 100 after it is formed. The improved surface hardness uniformity and increased corrosion resistance can be attributed to more than one sandblasting step used during the QPQ process. More than one sandblasting step forms a QPQ finish having layers with a more uniform thickness. The QPQ finish can include a nitride layer 230, a first oxide layer 120, and a second oxide layer 122. The method described above can produce a golf club head having a QPQ finish with a uniform nitride layer and oxide layers. More than one sandblasting step forms a more uniform nitride layer on the outer surface of the golf club head 100, followed by a more uniform first oxide layer 120, followed by a more uniform second oxide layer 122, as Figure 5E shown. More specifically, each sandblasting step flattens the surface, and each of the nitride layer 230, the first oxide layer 120, and the second oxide layer 122 crystallizes and forms on the surface. This will ensure that each layer has a more uniform thickness. No visible cracks are seen at arm's length viewing distance.

[0058] As mentioned above, the QPQ method described above can be applied to the golf club 100. The golf club can include a golf club head 100, a shaft, and a grip. The golf club head 100 can include a body having a striking face 104, a top rail 110 opposite the bottom 106, a toe opposite the heel, and a hosel 102 coupled to the club body and having a first end near the heel and a second end opposite the first end. The golf club head 100 can also include an outer surface. The QPQ method can be applied to a portion or the entire golf club head 100. The golf club head 100 as described herein treated with the QPQ method increases the degree to which the face and the head can be adjusted, while reducing surface deformation and increasing durability.

[0059] The surface hardness and corrosion resistance are improved by applying the following QPQ method during the manufacturing process. The QPQ method can include the following described and in Figure 1The steps illustrated in the figure. In the first step, the nitriding salt bath can be aged at a predetermined temperature for a predetermined amount of time. In the second step, the outer surface of the golf club head can be sandblasted. In the third step, the golf club head can be placed in a furnace and heated to a predetermined temperature for a predetermined amount of time. In the fourth step, the golf club head can be placed in the nitriding salt bath in the first furnace for a predetermined amount of time. The fourth step can also include forming a nitride layer 230 on the outer surface of the golf club head. In the fifth step, the temperature of the furnace can be reduced to a predetermined temperature for a predetermined amount of time to allow a first oxide layer 120 to form on top of the nitride layer 230. In the sixth step, the club head 100 can be removed from the furnace, cooled, and cleaned. In the seventh step, the outer surface of the golf club head 100 can be sandblasted. In the eighth step, the club head 100 can be placed in a furnace heated to a predetermined temperature for a predetermined amount of time. In the ninth step, the club head 100 can be placed back in the nitride salt, and a second oxide layer 122 can be formed on top of the first oxide layer 120. In the tenth step, the club head 100 can be removed from the furnace, cooled, and cleaned. In the eleventh step, the outer surface of the golf club head 100 can be sandblasted. These steps ensure that the golf club head has a finish that has a uniform nitride layer, first oxide layer, and second oxide layer 122.

[0060] More specifically, the first step can include aging the golf club head 100 in a nitriding salt bath (hereinafter optionally referred to as the "salt bath") at a predetermined temperature (hereinafter referred to as the "aging temperature") in the first furnace for a predetermined amount of time (hereinafter referred to as the "aging time"). The salt bath can include chemical compositions such as NaCNO, KCNO, Na2CO3, K2CO3, KCl, Li2CO3, and Na2SO4. The salt bath can include a combination of compounds, where the amount of each compound used in the salt bath is characterized by a percentage that indicates the proportion of the salt bath attributable to that compound. The percentage of each compound can affect how the outer surface of the golf club head reacts with the salt bath, and more specifically can affect how the nitride layer 230, first oxide layer 120, and second oxide layer 122 form.

[0061] In some embodiments, the salt bath contains 30%-60% NaCNO. In some embodiments, the percentage of NaCNO can be in the range from 30% to 35%, 35% to 40%, 40% to 45%, 45% to 50%, 50% to 55%, or 55% to 60%. In some embodiments, the percentage of NaCNO can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%. In one embodiment, the percentage of NaCNO is in the range from 35% to 55%.

[0062] In some embodiments, the salt bath contains 0.01% to 25% KCNO. In some embodiments, the percentage of KCNO can be in the range from 0.01% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, or 20% to 25%. In some embodiments, the percentage of KCNO can be 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 21%, 22%, 23%, 24%, or 25%. In one embodiment, the percentage of KCNO is in the range from 0% to 20%. In some embodiments, the percentage of KCNO in the salt bath can be less than 5%, less than 10%, less than 15%, less than 20%, or less than 25%.

[0063] In some embodiments, the salt bath contains 3% to 13% Na2CO3. In some embodiments, the percentage of Na2CO3 can be in the range from 3% to 5%, 5% to 7%, 7% to 9%, 9% to 11%, or 11% to 13%. In some embodiments, the percentage of Na2CO3 can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or 13%. In one embodiment, the percentage of Na2CO3 is in the range from 5% to 10%.

[0064] In some embodiments, the salt bath comprises 15% to 40% of K2CO3. In some embodiments, the percentage of K2CO3 can be in the range from 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, or 35% to 40%. In some embodiments, the percentage of K2CO3 can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%. In one embodiment, the percentage of K2CO3 is in the range from 20% to 35%.

[0065] In some embodiments, the salt bath comprises 0.01% to 20% of KCl. In some embodiments, the percentage of KCl can be in the range from 0.01% to 5%, 5% to 10%, 10% to 15%, or 15% to 20%. In some embodiments, the percentage of KCl can be 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. In some embodiments, the percentage of KCl in the salt bath can be less than 5%, less than 10%, less than 15%, or less than 20%. In one embodiment, the percentage of KCl is in the range from 0.01% to 15%.

[0066] In some embodiments, the salt bath comprises 0.01% to 15% of Li2CO3. In some embodiments, the percentage of Li2CO3 can be in the range from 0.01% to 5%, 5% to 10%, or 10% to 15%. In some embodiments, the percentage of Li2CO3 can be 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. In some embodiments, the percentage of Li2CO3 in the salt bath can be less than 5%, less than 10%, or less than 15%. In one embodiment, the percentage of Li2CO3 is in the range from 0.01% to 10%.

[0067] In some embodiments, the salt bath comprises 0.01% to 5% of Na2SO4. In some embodiments, the percentage of Na2SO4 can be in the range from 0.01% to 1%, 1% to 2%, 2% to 3%, 3% to 4%, or 4% to 5%. In some embodiments, the percentage of Na2SO4 can be 0.01%, 1%, 2%, 3%, 4%, or 5%. In some embodiments, the percentage of Na2SO4 in the salt bath can be less than 1%, less than 2%, less than 3%, less than 4%, or less than 5%. In one embodiment, the percentage of Na2SO4 is in the range from 0% to 2%. As discussed above, the percentage of the compound can affect how the surface of the outer surface reacts with the salt bath. More specifically, the percentage of the compound can affect the formation of the nitride layer 230 and the first oxide layer 120, thereby affecting the surface hardness and corrosion resistance of the outer surface.

[0068] As discussed above, the salt bath can be aged by heating the salt bath to an aging temperature for an aging time. The aging time can be between 5.00 hours and 7.00 hours. The aging time can be between 5.00 hours and 5.25 hours, between 5.25 hours and 5.50 hours, between 5.50 hours and 5.75 hours, between 5.75 hours and 6.00 hours, between 6.00 hours and 6.25 hours, between 6.25 hours and 6.50 hours, between 6.50 hours and 6.75 hours, or between 6.75 hours and 7.00 hours. In one embodiment, the aging time is 6.00 hours.

[0069] The aging temperature can be between 525 °C and 605 °C. The aging temperature can be between 525 °C and 535 °C, between 535 °C and 545 °C, between 545 °C and 555 °C, between 555 °C and 565 °C, between 565 °C and 575 °C, between 575 °C and 585 °C, between 585 °C and 595 °C, or between 595 °C and 605 °C. The aging temperature can be 525 °C, 526 °C, 527 °C, 528 °C, 529 °C, 530 °C, 531 °C, 532 °C, 533 °C, 534 °C, 535 °C, 536 °C, 537 °C, 538 °C, 539 °C, 540 °C, 541 °C, 542 °C, 543 °C, 544 °C, 545 °C, 546 °C, 547 °C, 548 °C, 549 °C, 550 °C, 551 °C, 552 °C, 553 °C, 554 °C, 555 °C, 556 °C, 557 °C, 558 °C, 559 °C, 560 °C, 561 °C, 562 °C, 563 °C, 564 °C, 565 °C, 566 °C, 567 °C, 568 °C, 569 °C, 570 °C, 571 °C, 572 °C, 573 °C, 574 °C, 575 °C, 576 °C, 577 °C, 578 °C, 579 °C, 580 °C, 581 °C, 582 °C, 583 °C, 584 °C, 585 °C, 586 °C, 587 °C, 588 °C, 589 °C, 590 °C, 591 °C, 592 °C, 593 °C, 594 °C, 595 °C, 596 °C, 597 °C, 598 °C, 599 °C, 600 °C, 601 °C, 602 °C, 603 °C, 604 °C, or 605 °C. In one embodiment, the aging temperature is 565 °C.

[0070] Salt bath aging at the specified time and temperature ensures that the CNO concentration is between 28% and 36%. In some embodiments, the CNO concentration is between 28% and 29%, between 29% and 30%, between 30% and 31%, between 31% and 32%, between 32% and 33%, between 33% and 34%, or between 35% and 36%. As Figure 2 shown, CNO decomposes during aging to provide nitrogen for forming the nitride layer 230.

[0071] The second step may include sandblasting the outer surface. This step may involve sandblasting the golf club with a medium selected from the group consisting of glass beads, sand, water, alumina, silicon carbide, steel shot, and any other suitable form of grit. The grit size may be between #60 grit and #320 grit. The grit size may be between #60 grit and #80 grit, between #80 grit and #100 grit, between #100 grit and #120 grit, between #120 grit and #140 grit, between #140 grit and #160 grit, between #160 grit and #180 grit, between #180 grit and #200 grit, between #200 grit and #220 grit, between #220 grit and #240 grit, between #240 grit and #260 grit, between #260 grit and #280 grit, between #280 grit and #300 grit, or between #300 grit and #320 grit. In one embodiment, the medium may be glass beads having a #80 grit. In one embodiment, the medium may be glass beads having a #220 grit.

[0072] In addition, the sandblasting may be performed under pressure. The pressure may be between 1 kg / cm 2 and 5 kg / cm 2 In some embodiments, the pressure may be between 1 kg / cm 2 and 2 kg / cm 2 between 2 kg / cm 2 and 3 kg / cm 2 between 3 kg / cm 2 and 4 kg / cm 2 or between 4 kg / cm 2 and 5 kg / cm 2 The pressure may be 1 kg / cm 2 2 kg / cm 2 3 kg / cm 2 4 kg / cm 2 or 5 kg / cm 2 In one embodiment, the sandblasting is performed at a pressure of 2 kg / cm 2 In some embodiments, the second step may involve first sandblasting the outer surface with a first medium having a first grit size at a first pressure, and then sandblasting the outer surface with a second medium having a second grit size at a second pressure. The sandblasting can ensure that the outer surface is uniform by reducing local areas of excessive buildup of the outer layer. A uniform outer surface at this location in the process can allow for greater uniformity in the formation of the nitride layer 230 and the first oxide layer 120, which subsequently grow from the surface.

[0073] In some embodiments, the second step may further include loading the golf club head 100 into a holding fixture. In one exemplary embodiment, the holding fixture may consist of a tree fixture. The tree fixture may allow multiple golf club heads to be processed at any given time.

[0074] The third step may involve placing the holding fixture into a second furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time. The time and temperature may be selected to ensure that little to no moisture remains on or in the golf club head 100. The predetermined temperature may be between 325°C and 375°C. In one embodiment, the predetermined temperature may be between 325°C and 330°C, between 330°C and 335°C, between 335°C and 340°C, between 340°C and 345°C, between 345°C and 350°C, between 350°C and 355°C, between 355°C and 360°C, between 360°C and 365°C, between 365°C and 370°C, or between 370°C and 375°C. In one instance, the predetermined temperature may be 350°C. The predetermined heating time may be between 25 minutes and 35 minutes. The predetermined time may be between 25 minutes and 26 minutes, between 26 minutes and 27 minutes, between 27 minutes and 28 minutes, between 28 minutes and 29 minutes, between 29 minutes and 30 minutes, between 30 minutes and 31 minutes, between 31 minutes and 32 minutes, between 32 minutes and 33 minutes, between 33 minutes and 34 minutes, or between 34 minutes and 35 minutes. The time and temperature are selected to allow the environment of the pit furnace to equilibrate. This step can ensure that little to no moisture is on or in the golf club head 100, thereby improving the bonding ability of the second oxide layer 122, as discussed in further detail below.

[0075] The fourth step may involve moving the holding fixture from the second furnace to the first furnace, immersing the holding fixture in a salt bath, and allowing the holding fixture to remain in the first furnace for a predetermined amount of time. The predetermined time may be long enough to allow a nitride layer 230 to form on the outer surface of the golf club head.

[0076] The predetermined temperature used in the fourth step can be between 500 °C and 650 °C. In one embodiment, the predetermined temperature can be between 500 °C and 525 °C, between 525 °C and 550 °C, between 550 °C and 575 °C, between 575 °C and 600 °C, between 600 °C and 625 °C, or between 625 °C and 650 °C. In one example, the predetermined temperature can be 580 °C. The predetermined time used in the fourth step can be between 35 minutes and 55 minutes. In some embodiments, the predetermined time can be between 35 minutes and 40 minutes, between 40 minutes and 45 minutes, between 45 minutes and 50 minutes, or between 50 minutes and 55 minutes. The time and temperature are selected to allow for the complete formation of the nitride layer 230.

[0077] The nitride layer 230 is formed by a chemical reaction between the salt bath and the outer surface. The chemical equation can be seen in Figure 2 As described above in step 1, the salt bath is preheated at a predetermined temperature for a predetermined amount of time. This process allows nitrogen to be separated from the chemical compound, as Figure 2 illustrated. The golf club head 100 is introduced into the salt bath, and additional heat is applied, allowing nitrogen to diffuse into the outer surface. As discussed above in step 2, the uniform outer surface created by sandblasting allows nitrogen to easily diffuse into the outer surface. Nitrogen diffuses into the outer surface of the golf club head to form the nitride layer 230.

[0078] The nitride layer 230 can include both mechanical and physical properties that can affect the durability and performance of the finished golf club head 100. The mechanical properties can include, but are not limited to, the hardness and uniformity of the nitride layer 230 (optionally referred to hereinafter as "nitride uniformity"). Uniformity can mean that the thickness of the layer is substantially the same throughout the layer. Uniformity can be quantified by the difference between the maximum nitride thickness and the minimum nitride thickness. The physical properties can include, but are not limited to, the nitride thickness, the maximum nitride thickness, and the minimum nitride thickness.

[0079] The nitride thickness can be defined as the distance from the portion where the nitride layer 230 abuts the core 110 to the portion where the nitride layer 230 abuts the first oxide layer 120. The nitride thickness can be between 0.00025 inches and 0.00060 inches. The nitride thickness can be between 0.00025 inches and 0.00030 inches, between 0.00030 inches and 0.00035 inches, between 0.00035 inches and 0.00040 inches, between 0.00040 inches and 0.00045 inches, between 0.00045 inches and 0.00050 inches, between 0.00050 inches and 0.00055 inches, between 0.00055 inches and 0.00060 inches, or between 0.00060 inches and 0.00065 inches. As discussed above, the nitride thickness can affect the durability and performance of the QPQ finish. More specifically, too large a nitride thickness can increase the force required to adjust the clubface and clubhead. The increased force can cause the QPQ finish to be overstressed, increasing cracking during clubface / clubhead adjustment. Additionally, too thin a nitride thickness may not be strong enough and may thus crack in response to the applied force during clubface / clubhead adjustment. Further, the QPQ finish tends to be a brittle finish, and thus, as the thickness of the nitride layer 230 increases, the likelihood of larger cracks 108 and the ease with which these cracks 108 form also increase.

[0080] The nitride layer 230 can also include a nitride maximum thickness and a nitride minimum thickness. The nitride maximum thickness can be defined as the maximum distance from the portion where the nitride layer 230 abuts the core 110 to the portion where the nitride layer 230 abuts the first oxide layer 120. The nitride maximum thickness can be measured in a direction perpendicular to the nitride layer 230 at the location where the measurement is taken. The nitride maximum thickness can be between 0.00025 inches and 0.00045 inches.

[0081] The nitride minimum thickness can be defined as the minimum distance from the portion where the nitride layer 230 abuts the core 110 to the portion where the nitride layer 230 abuts the first oxide layer 120. The nitride minimum thickness can be measured in a direction perpendicular to the nitride layer 230 at the location where the measurement is taken. The nitride minimum thickness can be between 0.00045 inches and 0.00060 inches.

[0082] The nitride layer 230 may also include nitride uniformity, which is defined herein as the ratio between the maximum thickness and the minimum thickness. The uniformity may be between 1.00 and 1.25. The uniformity may be between 1.00 and 1.05, between 1.05 and 1.10, between 1.10 and 1.15, between 1.15 and 1.20, or between 1.20 and 1.25. The uniformity may be less than 1.25, less than 1.20, less than 1.15, or less than 1.10. The closer the uniformity is to 1, the more uniform the nitride thickness. The nitride uniformity may be further ensured by providing a consistent and uniform surface for the first oxide layer 120 to grow from. Any uniformity or lack of uniformity in the nitride layer 230 may be directly translated into the uniformity of the first oxide layer 120.

[0083] The fifth step can involve reducing the temperature of the furnace to a predetermined temperature for a predetermined amount of time to allow a first oxide layer 120 to form on top of the nitride layer 230, as discussed above. The predetermined temperature can be between 345 °C and 415 °C. In some embodiments, the predetermined temperature can be between 345 °C and 350 °C, between 350 °C and 355 °C, between 355 °C and 360 °C, between 360 °C and 365 °C, between 365 °C and 370 °C, between 370 °C and 375 °C, between 375 °C and 380 °C, between 380 °C and 385 °C, between 385 °C and 390 °C, between 390 °C and 395 °C, between 395 °C and 400 °C, between 400 °C and 405 °C, or between 405 °C and 410 °C. The predetermined temperature can be 345 °C, 346 °C, 347 °C, 348 °C, 349 °C, 350 °C, 351 °C, 352 °C, 353 °C, 354 °C, 355 °C, 356 °C, 357 °C, 358 °C, 359 °C, 360 °C, 361 °C, 362 °C, 363 °C, 364 °C, 365 °C, 366 °C, 367 °C, 368 °C, 369 °C, 370 °C, 371 °C, 372 °C, 373 °C, 374 °C, 375 °C, 376 °C, 377 °C, 378 °C, 379 °C, 380 °C, 381 °C, 382 °C, 383 °C, 384 °C, 385 °C, 386 °C, 387 °C, 388 °C, 389 °C, 390 °C, 391 °C, 392 °C, 393 °C, 394 °C, 395 °C, 396 °C, 397 °C, 398 °C, 399 °C, 400 °C, 401 °C, 402 °C, 403 °C, 404 °C, 405 °C, 406 °C, 407 °C, 408 °C, 409 °C, 410 °C, 411 °C, 412 °C, 413 °C, 414 °C, or 415 °C. In one embodiment, the predetermined temperature can be 410 °C. In another embodiment, the predetermined temperature can be 350 °C. The predetermined time can be between 25 minutes and 35 minutes. The predetermined time can be between 25 minutes and 26 minutes, between 26 minutes and 27 minutes, between 27 minutes and 28 minutes, between 28 minutes and 29 minutes, between 29 minutes and 30 minutes, between 30 minutes and 31 minutes, between 31 minutes and 32 minutes, between 32 minutes and 33 minutes, between 33 minutes and 34 minutes, or between 34 minutes and 35 minutes. In one embodiment, the predetermined time is 30 minutes. The time and temperature are selected to fully form the first oxide layer 120. A chemical reaction can occur such that the first oxide layer 120 can form on the outer surface of the club head, which is on top of the nitride layer 230, as mentioned above. The relevant chemical reaction can be seen in Figure 3 as follows.

[0084] The first oxide layer 120 may include both mechanical and physical properties that can affect the durability and performance of the finished golf club head 100. The mechanical properties may include, but are not limited to, the hardness and uniformity of the first oxide layer 120. The physical properties may include, but are not limited to, the first oxide maximum thickness, the first oxide minimum thickness, and the uniformity of the first oxide layer 120 (optionally referred to hereinafter as "first oxide uniformity").

[0085] The first oxide thickness may be defined as the distance from the location where the first oxide layer 120 abuts the nitride layer 230 to the location where the first oxide layer 120 abuts the second oxide layer 122. The first oxide thickness may be between 0.000045 inches and 0.000115 inches. The first oxide thickness may be between 0.000045 inches and 0.000055 inches, between 0.000055 inches and 0.000065 inches, between 0.000065 inches and 0.000075 inches, between 0.000075 inches and 0.000085 inches, between 0.000085 inches and 0.000095 inches, between 0.000095 inches and 0.000105 inches, or between 0.000105 inches and 0.000115 inches. The first oxide thickness may be less than 0.000115 inches, less than 0.000105 inches, less than 0.000105 inches, less than 0.000095 inches, less than 0.000085 inches, less than 0.00075 inches, or less than 0.000065 inches.

[0086] The first oxide maximum thickness may be defined as the maximum distance from the location where the first oxide layer 120 abuts the nitride layer 230 to the location where the first oxide layer 120 abuts the second oxide layer 122. The first oxide maximum thickness may be measured in a direction perpendicular to the nitride layer 230 at the location where the measurement is taken. The first oxide maximum thickness may be between 0.000075 inches and 0.000115 inches.

[0087] The first oxide minimum thickness may be defined as the minimum distance from the location where the first oxide layer 120 abuts the nitride layer 230 to the location where the first oxide layer 120 abuts the second oxide layer 122. The first oxide minimum thickness may be measured in a direction perpendicular to the nitride layer 230 at the location where the measurement is taken. The first oxide maximum thickness may be between 0.000050 inches and 0.000075 inches.

[0088] The first oxide uniformity may refer to that the thickness of the layer is substantially the same throughout the layer. The first oxide uniformity can be quantified by the difference between the maximum thickness of the first oxide and the minimum thickness of the first oxide. The uniformity can be between 1.00 and 1.85. The uniformity can be between 1.00 and 1.15, between 1.15 and 1.30, between 1.30 and 1.45, between 1.45 and 1.60, between 1.60 and 1.65, between 1.65 and 1.80, or between 1.80 and 1.95. The uniformity can be less than 1.95, less than 1.80, less than 1.65, or less than 1.50. The closer the uniformity is to 1, the more uniform the first oxide thickness is.

[0089] The sixth step may involve removing the holding fixture from the first furnace and cooling the club head 100 to a predetermined temperature. In some embodiments, the cooling can be achieved by allowing the club head 100 to air cool. In other embodiments, the club head 100 can be cooled by partially or completely immersing the club head 100 in a medium. The medium can be a gas or a liquid. In one embodiment, the medium is an inert gas. The predetermined temperature can be between 60°C and 100°C. In some embodiments, the predetermined temperature can be between 60°C and 65°C, between 65°C and 70°C, between 70°C and 75°C, between 75°C and 80°C, between 80°C and 85°C, between 90°C and 95°C, or between 95°C and 100°C.

[0090] The club head 100 can be cooled over a specified period of time. The period of time can range from 20 minutes to 40 minutes. In some embodiments, the cooling can be carried out over a period of time in the range from 20 minutes to 25 minutes, 25 minutes to 30 minutes, 30 minutes to 35 minutes, or 35 minutes to 40 minutes. After the club head 100 is cooled, the club head 100 can be rinsed with water and then unloaded from the holding fixture.

[0091] The seventh step may involve sandblasting the outer surface to ensure the uniformity of the entire first oxide layer 120. This step may involve sandblasting the golf club with a medium selected from the group consisting of glass beads, sand, alumina, silicon carbide, steel shot, and any other suitable form of grit. The medium may also include a grit size. The grit size may be between #60 grit and #320 grit. The grit size may be between #60 grit and #80 grit, between #80 grit and #100 grit, between #100 grit and #120 grit, between #120 grit and #140 grit, between #140 grit and #160 grit, between #160 grit and #180 grit, between #180 grit and #200 grit, between #200 grit and #220 grit, between #220 grit and #240 grit, between #240 grit and #260 grit, between #260 grit and #280 grit, between #280 grit and #300 grit, or between #300 grit and #320 grit. In one exemplary embodiment, the medium may be glass beads with a #80 grit size. In one exemplary embodiment, the medium may be glass beads with a #220 grit size.

[0092] In addition, the sandblasting may be performed at a specified pressure. The pressure may be between 1 kg / cm 2 and 5 kg / cm 2 In some embodiments, the pressure may be between 1 kg / cm 2 and 2 kg / cm 2 between 2 kg / cm 2 and 3 kg / cm 2 between 3 kg / cm 2 and 4 kg / cm 2 or between 4 kg / cm 2 and 5 kg / cm 2 In one exemplary embodiment, the sandblasting is performed at a pressure of 2.5 kg / cm 2 . In some embodiments, the eighth step may involve first sandblasting the outer surface with a first medium having a first grit size at a first pressure, and then sandblasting the outer surface with a second medium having a second grit size at a second pressure. In one exemplary embodiment, the eighth step may involve sandblasting the outer surface with glass beads of #80 grit size at a pressure of 2.5 kg / cm 2 , and then at 2.5 kg / cm 2The surface is sandblasted with #220 grit glass beads. As discussed above, sandblasting ensures that the first oxide layer 120 is uniform. A uniform first oxide layer 120 can allow for greater uniformity in the formation of the second oxide layer 122, thereby ensuring uniform strength across the outer surface of the golf club head.

[0093] The seventh step can also involve visually inspecting the golf club head 100 to ensure uniformity. As discussed above, ensuring uniformity in this step can further ensure more uniform formation of the second oxide layer 122, thereby ensuring uniform strength across the outer surface of the golf club head. Each layer (nitride, first oxide, and second oxide) can have this step to ensure uniformity (close to 1) to ensure that each layer works in concert with the others to mitigate crack migration.

[0094] In some embodiments, the seventh step can also involve loading the golf club head 100 into a holding fixture. In one exemplary embodiment, the holding fixture can consist of a tree fixture. As previously discussed, a tree fixture enables the ability to process multiple golf club heads at any given time.

[0095] The eighth step can involve placing the holding fixture into a second heating furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time. The time and temperature can be selected to ensure that no moisture remains on or in the golf club head 100. The predetermined temperature can be between 325°C and 375°C. In one embodiment, the predetermined temperature can be between 325°C and 330°C, between 330°C and 335°C, between 335°C and 340°C, between 340°C and 345°C, between 345°C and 350°C, between 350°C and 355°C, between 355°C and 360°C, between 360°C and 365°C, between 365°C and 370°C, or between 370°C and 375°C. In one instance, the predetermined temperature can be 350°C. The predetermined time can be between 25 minutes and 35 minutes. In one embodiment, the predetermined time can be between 25 minutes and 26 minutes, between 26 minutes and 27 minutes, between 27 minutes and 28 minutes, between 28 minutes and 29 minutes, between 29 minutes and 30 minutes, between 30 minutes and 31 minutes, between 31 minutes and 32 minutes, between 32 minutes and 33 minutes, between 33 minutes and 34 minutes, or between 34 minutes and 35 minutes. The time and temperature are selected to allow the environment of the pit furnace to equilibrate. This step can ensure little to no moisture on or in the golf club head 100, thereby improving the bonding ability of the second oxide layer 122, as discussed in more detail below.

[0096] The ninth step can involve moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the second furnace for a continuously predetermined amount of time. The predetermined time can be long enough to allow a second oxide layer 122 to form on the outer surface of the golf club head. The chemical equation showing the chemical reaction that occurs during this step can be seen in Figure 3 below.

[0097] The second oxide layer 122 can include both mechanical and physical properties that can affect the durability and performance of the finished golf club head 100. This layer is exposed to the elements and provides the visual aesthetic of a QPQ finish on the golf club head 100. The mechanical properties can include, but are not limited to, the hardness and thickness of the second oxide layer 122. The physical properties can include, but are not limited to, the maximum second oxide thickness, the minimum second oxide thickness, and the uniformity of the second oxide layer 122 (optionally referred to hereinafter as "second oxide uniformity"). Second oxide uniformity can refer to the thickness of the layer being substantially the same throughout the layer. Second oxide uniformity can be quantified by the difference between the maximum second oxide thickness and the minimum second oxide thickness.

[0098] The second oxide layer 122 can include both mechanical and physical properties that can affect the durability and performance of the finished golf club head 100. The mechanical properties can include, but are not limited to, the hardness and uniformity of the second oxide layer 122 (optionally referred to hereinafter as "second oxide uniformity"). Second oxide uniformity can refer to the thickness of the layer being substantially the same throughout the layer. Second oxide uniformity can be quantified by the difference between the maximum second oxide thickness and the minimum second oxide thickness. The physical properties can include, but are not limited to, the second oxide thickness, the maximum second oxide thickness, and the minimum second oxide thickness.

[0099] The second oxide thickness can be defined as the distance from the location where the second oxide layer 122 interfaces with the first oxide layer 120 to the location where the second oxide layer 122 interfaces with the outer surface. The second oxide thickness can be between 0.000045 inches and 0.000115 inches. The second oxide thickness can be between 0.000045 inches and 0.000055 inches, between 0.000055 inches and 0.000065 inches, between 0.000065 inches and 0.000075 inches, between 0.000075 inches and 0.000085 inches, between 0.000085 inches and 0.000095 inches, between 0.000095 inches and 0.000105 inches, or between 0.000105 inches and 0.000115 inches. The first oxide thickness can be less than 0.000115 inches, less than 0.000105 inches, less than 0.000105 inches, less than 0.000095 inches, less than 0.000085 inches, less than 0.00075 inches, or less than 0.000065 inches.

[0100] The second oxide maximum thickness can be defined as the maximum distance from the location where the second oxide layer 122 interfaces with the first oxide layer 120 to the location where the second oxide layer 122 interfaces with the outer surface. The second oxide maximum thickness can be measured in a direction perpendicular to the second oxide layer 122 at the location where the measurement is taken. The second oxide maximum thickness can be between 0.000075 inches and 0.000115 inches.

[0101] The second oxide minimum thickness can be defined as the minimum distance from the location where the second oxide layer 122 interfaces with the first oxide layer 120 to the location where the second oxide layer 122 interfaces with the outer surface. The second oxide minimum thickness can be measured in a direction perpendicular to the nitride layer 230 at the location where the measurement is taken. The second oxide minimum thickness can be between 0.000050 inches and 0.000075 inches.

[0102] As previously mentioned, the second oxide layer 122 includes second oxide uniformity. The second oxide uniformity can be defined as the ratio between the second oxide maximum thickness and the second oxide minimum thickness. The uniformity can be between 1.00 and 1.65. The uniformity can be between 1.00 and 1.15, between 1.15 and 1.30, between 1.30 and 1.45, between 1.45 and 1.60, or between 1.60 and 1.65. The uniformity can be less than 1.65, less than 1.50, less than 1.45, or less than 1.30. The closer the uniformity is to 1, the more uniform the second oxide thickness.

[0103] The tenth step may involve removing the holding fixture from the first furnace and cooling the club head 100 to a predetermined temperature. In some embodiments, the cooling may be achieved by allowing the club head 100 to air cool. In other embodiments, the club head 100 may be cooled by partially or fully immersing the club head 100 in a medium. The predetermined temperature may be between 60°C and 100°C. In some embodiments, the predetermined temperature may be between 60°C and 65°C, between 65°C and 70°C, between 70°C and 75°C, between 80°C and 85°C, between 90°C and 95°C, or between 95°C and 100°C.

[0104] The club head 100 may be cooled over a period of time. The period of time may range from 20 minutes to 40 minutes. In some embodiments, the cooling may be carried out over a period of time ranging from 20 minutes to 25 minutes, 25 minutes to 30 minutes, 30 minutes to 35 minutes, or 35 minutes to 40 minutes. After the club head 100 is cooled, the club head 100 may be rinsed with water and then unloaded from the holding fixture.

[0105] In some embodiments, the tenth step may also involve allowing the club head 100 to air dry. The club head 100 may be allowed to air dry until it reaches room temperature. In some embodiments, the room temperature may be between 20°C and 35°C. In some embodiments, the room temperature may be between 20°C and 25°C, between 25°C and 30°C, or between 30°C and 35°C.

[0106] The eleventh step may involve sandblasting the outer surface to ensure the uniformity of the entire second oxide layer 122. This step may involve sandblasting the golf club with a medium selected from the group consisting of glass beads, sand, alumina, silicon carbide, steel shot, and any other suitable form of grit. The grit size may be between #60 grit and #320 grit. The grit size may be between #60 grit and #80 grit, between #80 grit and #100 grit, between #100 grit and #120 grit, between #120 grit and #140 grit, between #140 grit and #160 grit, between #160 grit and #180 grit, between #180 grit and #200 grit, between #200 grit and #220 grit, between #220 grit and #240 grit, between #240 grit and #260 grit, between #260 grit and #280 grit, between #280 grit and #300 grit, or between #300 grit and #320 grit. In one exemplary embodiment, the medium may be glass beads with a #220 grit size.

[0107] In addition, the sandblasting may be carried out under pressure. The pressure may be 1 kg / cm 2and 5 kg / cm 2 between. In one embodiment, the pressure can be between 1 kg / cm 2 and 2 kg / cm 2 between, between 2 kg / cm 2 and 3 kg / cm 2 between, between 3 kg / cm 2 and 4 kg / cm 2 between or between 4 kg / cm 2 and 5 kg / cm 2 between. In one exemplary embodiment, the sandblasting is performed at a pressure of 2 kg / cm 2 In another exemplary embodiment, the sandblasting can be performed at a pressure of 3 kg / cm 2 In some embodiments, the fifteenth step can involve first sandblasting the outer surface with a first medium having a first grit size at a first pressure and then sandblasting the outer surface with a second medium having a second grit size at a second pressure. As discussed above, sandblasting can ensure the uniformity of the entire second oxide layer 122, thus ensuring the uniform strength of the outer surface of the entire golf club head.

[0108] In some embodiments, the eleventh step can further include visually inspecting each golf club head 100 to ensure uniformity, similar to the ninth step. The uniformity of the second oxide layer 122 can ensure that the surface hardness is uniform, thereby eliminating or minimizing the formation of cracks 108 formed during face / head adjustment.

[0109] The implementation of the method is as follows: 1) Aging the nitriding salt to a temperature of 565°C for 6 hours, 2) Blasting the outer surface of the golf club head, 3) Placing the golf club head into a holding fixture, 4) Placing the holding fixture into a second furnace and heating the second furnace to 350°C for 30 minutes, 5) Moving the holding fixture from the second furnace to the first furnace and maintaining the furnace at 580°C for 45 minutes to form a nitride layer, 6) Reducing the temperature of the furnace to 410°C and maintaining the temperature there for 30 minutes to form a first oxide layer on top of the nitride layer, 7) Removing the holding fixture from the first furnace, cooling the golf club head to a temperature, cleaning the golf club head, and unloading the golf club head from the holding fixture, 8) Blasting the outer surface of the golf club head, 9) Visually inspecting the golf club head to ensure the uniformity of the outer surface, 10) Reloading the golf club head into the holding fixture, 11) Placing the holding fixture in the second furnace and heating the second furnace at 410°C for 45 minutes to form a second oxide layer, 12) Moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the first furnace for a predetermined amount of time, 13) Removing the holding fixture from the first furnace, cooling the golf club head to a predetermined temperature, and cleaning the golf club head, 14) Allowing the golf club head to air dry, 15) Blasting the outer surface of the golf club head, and 16) Visually inspecting the golf club head to ensure the uniformity of the outer surface.

[0110] The method described above can ensure increased uniformity in the formation of each of the nitride layer 230, the first oxide layer 120, and the second oxide layer 122. The increased uniformity of the above layers, and more specifically, the increased uniformity of the layer thickness, can allow for an increase in the integrity of the layers, resulting in an improvement in the mechanical properties of the outer surface of the golf club head.

[0111] The increased uniformity in the formation of the nitride layer 230, the first oxide layer 120, and the second oxide layer 122 results in an improvement in the uniformity of the hardness of the QPQ finish. The hardness of the QPQ finish can be between 55 HRC and 65 HRC. The hardness of the QPQ finish can be between 55 HRC and 60 HRC or between 60 HRC and 65 HRC. The hardness can be 55 HRC, 56 HRC, 57 HRC, 58 HRC, 59 HRC, 60 HRC, 61 HRC, 62 HRC, 63 HRC, 64 HRC, or 65 HRC. The QPQ finish as described herein can result in a 27% increase in hardness. The QPQ finish as described herein can result in an improvement in the hardness change of up to 36%, thereby improving the hardness uniformity of the entire QPQ finish.

[0112]

[0113] Table 1: Images of levels 1-5, depicting the degree and depth of porosity within the compound layer.

[0114] The methods described above can produce golf club heads having graded compound layers or layers. The compound layer grade or layer grade can refer to a QPQ finish, and more specifically to the nitride layer 230 and the first oxide layer 120 and the second oxide layer 122. The compound layer grade describes the degree and distribution of porosity within the compound layer. Levels 1, 2, and 3 are considered to be within an acceptable range of porosity. Levels 4 and 5 are considered to contain too many pores to reliably prevent undesired surface deformation. Specifically, levels 1 and 2 describe a dense compound layer having few to no micropores on the surface. Level 3 refers to a dense compound layer having micropores that gradually decrease from the upper layer into the material. Levels 4 and 5 describe a compound layer in which more than 2 / 3 of the compound layer is occupied by micropores. In some instances, a golf club head as described herein can include a level 3 compound layer. In some instances, a golf club head as described herein can include a level 2 compound layer. In some instances, a golf club head as described herein can include a level 1 compound layer. A golf club head as described herein can include a level 1, 2, or 3 compound layer. A golf club head as described herein does not include a level 4 or 5 compound layer.

[0115] The grade of the compound layer can be affected by the porosity level in the upper half of the compound layer (at least partially including the first oxide layer 120 and the second oxide layer 122) and the porosity level in the lower half of the compound layer (at least partially including the nitride layer 130). A high porosity level exhibited at and near the surface is an intended effect of the QPQ process and allows surface deformation, including the formation of microcracks. A significant difference in the severity of surface deformation and cracks beyond microcracks is caused by a significant difference in porosity deeper below the upper half of the compound layer.

[0116] The porosity within the lower half of the compound layer can create interstitial spaces that allow microcracks formed at the surface to extend deeper into the material. Thus, it may be desirable to have little to no porosity within the lower half of the compound layer. The percentage of porosity within the lower half of the compound layer can be between 0% and 5%. The percentage of porosity within the lower half of the compound layer can be between 0% and 1%, between 1% and 2%, between 2% and 3%, between 3% and 4%, or between 4% and 5%. The percentage of porosity within the lower half of the compound layer can be less than 5%, less than 3%, less than 2%, less than 1%. The low percentage of porosity within the lower half of the compound layer results in a very low chance that the microcracks formed in the upper half will connect with any of the few interstitial spaces formed by the porosity in the lower half, such that the likelihood that the cracks will deepen to extend into the lower half and become visible to the naked eye at the arm length is very low.

[0117] The percentage of porosity within the upper half of the compound can be between 40% and 65%. The percentage of porosity within the upper half of the compound layer can be between 40% and 45%, between 45% and 55%, between 55% and 60%, or between 60% and 65%. Although the high level of porosity exhibited within the upper half of the compound layer is an intended effect of the QPQ process and allows surface deformation, including the formation of microcracks, the propagation and deepening of the microcracks into the lower half of the compound layer are prevented.

[0118] The application of the method described herein can improve the hardness uniformity and wear resistance of the outer surface of a golf club head while still allowing the core 110 to remain softer and more ductile. This is extremely important for a golf club head in order to maintain the flexibility of the adjustable face / head as well as the desired feel and sound characteristics. The application of the QPQ method can allow the golf club head 100, including the outer surface, to have the ability to withstand the forces applied during impact and during the face / head adjustment process without affecting the feel of the golf club head 100 during impact.

[0119] The heat treatment of metals increases hardness while also increasing porosity. Porosity increases the likelihood of crack 108 by creating gaps in the material. Porosity near the surface allows for the generation of microcracks. However, the presence of greater porosity in regions deeper beneath the material surface allows cracks to further extend into the material, resulting in longer and wider cracks. Specifically, microcracks connected to the gaps created by porosity gain volume (depth and width) from the gaps. These longer and wider cracks are more likely to combine or interconnect to further extend along the surface, thereby increasing visibility and reducing integrity. Due to the increased frequency of gap appearance within the material, a greater percentage of porosity beyond the surface region leads to an increased frequency of deep cracks. A low percentage of porosity may result in cracks extending to the same maximum depth as materials with a greater percentage of porosity but will exhibit significantly fewer deep cracks, thus maintaining durability.

[0120] Typical QPQ methods result in a hardened surface, including regions with increased porosity that extend deeper into the material. The QPQ method described above produces an ideal hardened surface while maintaining high porosity, which results in increased hardness very close to the surface. Therefore, cracks are desirably less likely to extend deeply beneath the surface or away from the surface. When bent, the QPQ-treated surface is more likely to exhibit a series of microcracks rather than thick deep cracks, thus maintaining elasticity while providing the hardness produced by the QPQ process. Examples

[0121] Example I: Comparison between a conventional layer and an exemplary layer

[0122] A comparison of the physical properties of a control golf club head produced using a conventional QPQ method detailed in Table 2 below and an exemplary golf club head produced using the QPQ method detailed in Table 3 below is described herein. More specifically, this example shows differences in the thickness and uniformity of the nitride layer, the first oxide layer, and the second oxide layer.

[0123]

[0124] As Figure 5E and Figure 6E shown, magnified images of the outer surface of the golf club head are taken. Figure 5E An enlarged image of the exemplary golf club head is shown, while Figure 6EDisplays enlarged images of the control golf club head. Each image is used to measure the depths of the nitride layer, the first oxide layer, and the second oxide layer at selected locations. These values are then used to calculate the thicknesses of the nitride layer, the first oxide layer, and the second oxide layer at each selected location. There are four selected locations, which produces four data points for each layer. The four data points are used to determine the minimum and maximum thickness values for each layer of each golf club head. Then the ratio of the maximum thickness to the minimum thickness is taken to determine the uniformity. Additionally, the standard deviation of the four data points is determined to further show the variation in the thickness of each layer of each golf club head. The results can be seen in Tables 4, 5, and 6 below.

[0125]

[0126]

[0127] Table 4: Comparison of Nitride Layers between Control Golf Club Head and Exemplary Golf Club Head

[0128] As shown in Table 4 above, the exemplary golf club head produced a 34.99% improvement in the uniformity of the nitride layer relative to the control golf club head. The uniformity of the nitride layer further ensures the uniformity of the first oxide layer and the second oxide layer by providing a consistent surface for the first oxide layer to expand and grow. Any uniformity in the nitride layer can be directly transferred to the first oxide layer and then to the second oxide layer. Additionally, the exemplary golf club head produced a 67.83% improvement in the standard deviation of the nitride layer thickness relative to the control golf club head. The significant improvement in the standard deviation of the nitride layer thickness further shows the uniformity of the nitride layer thickness, as the standard deviation measures the amount of variation in thickness.

[0129] Control club head Exemplary club head Maximum thickness of the first oxide layer (in) 0.000165 0.0001033 Minimum thickness of the first oxide layer (in) 0.000091 0.0000559 Average thickness (in) 0.000125 0.0000796 Uniformity of the first oxide layer 1.813 1.848 Standard deviation of the first oxide 0.00002804 0.00001676

[0130] Table 5: Comparison of First Oxide Layers between Control Golf Club Head and Exemplary Golf Club Head

[0131] As shown in Table 5 above, the exemplary golf club head produced a 1.93% decrease in the uniformity of the first oxide layer. However, the exemplary golf club head did produce a 40.23% improvement in the standard deviation of the first oxide layer thickness relative to the control golf club head. Due to the significant improvement in the standard deviation of the first oxide layer thickness relative to the control golf club head, the decrease in uniformity is considered negligible. As previously mentioned, the standard deviation of the first oxide layer thickness shows the uniformity of the first oxide layer thickness, as the standard deviation measures the amount of variation in thickness.

[0132] In addition, as shown in Table 5 above, the average thickness of the exemplary first oxide layer is much smaller than that of the control first oxide layer.

[0133] The smaller average thickness provides a thinner first oxide layer that is less brittle and less prone to developing large cracks.

[0134] Control club head Exemplary club head Maximum thickness of the second oxide (in) 0.000165 0.0001033 Minimum thickness of the second oxide (in) 0.000091 0.0000456 Average thickness (in) 0.000147 0.00005745 Uniformity of the second oxide layer 1.813 1.594 Standard deviation of the second oxide 0.00001753 0.00001419

[0135] Table 6: Comparison of the second oxide layer between the control golf club head and the exemplary golf club head

[0136] As shown in Table 6 above, the exemplary golf club head produced a 12.08% improvement in the uniformity of the second oxide layer. In addition, the exemplary golf club head produced a 19.05% improvement in the standard deviation of the second oxide layer thickness relative to the control club head. The significant improvement in the standard deviation of the first oxide layer thickness relative to the control golf club head further demonstrates the uniformity of the second oxide layer thickness, as the standard deviation measures the amount of variation in thickness.

[0137] In addition, as shown in Table 6 above, the average thickness of the exemplary second oxide layer is much smaller than that of the control second oxide layer. The smaller average thickness provides a thinner second oxide layer that is less brittle and less prone to developing large cracks.

[0138] In summary, the additional sandblasting step of the QPQ method described herein shows an increase in the uniformity of each of the nitride layer, the first oxide layer, and the second oxide layer. This increased uniformity promotes the bonding of each layer, reduces porosity, and increases hardness, as detailed below in Examples II and V. Specifically, the smooth surface produced by the sandblasting step prevents the formation of defects between the layers within the compound layer, thereby reducing the frequency of deep crack formation, as detailed below in Examples III and IV.

[0139] Example II: Comparison of Porosity within the Compound Layer Produced by the QPQ Method Described herein and the Conventional QPQ Method

[0140] Example II provides a comparison of the degree and depth of porosity within the compound layer or finish layer applied to the surface of a golf club head using the method described herein and the conventional QPQ method. Two samples of a single exemplary embodiment of a golf club head having a one-piece ferrule structure made of 8620 steel alloy and receiving a post-manufacture QPQ treatment (hereinafter referred to as "exemplary club head 1" and "exemplary club head 2") are described herein, as described in the steps above and in Figure 1 the steps detailed therein. Specifically, the exemplary golf club head is treated using the steps detailed in Table 3 of Example I above.

[0141] The depth and extent of porosity of exemplary club head 1 and exemplary club head 2 are compared with the depth and extent of porosity of two samples of similar golf club heads that have received a conventional QPQ treatment (hereinafter referred to as "control club head 1" and "control club head 2"). The conventional QPQ treatment consists of the steps described in Table 2 of Example I above.

[0142]

[0143] Table 7: Summary of compound layer grades and porosity percentages of control club heads and exemplary club heads

[0144] Referring again to Table 7 above, control club head 1 and control club head 2 show high levels of porosity in the upper half of the compound layer, 39% and 47% respectively. Exemplary club head 1 and exemplary club head 2 similarly show high levels of porosity in the upper half of the compound layer, 59% and 45% respectively. The high levels of porosity exhibited at and near the surface are an expected effect of any QPQ process and allow surface deformation, including the formation of microcracks. The significant differences in the severity of surface deformation and cracks beyond microcracks are caused by significant differences in porosity deeper below the upper half of the compound layer.

[0145] Referring again to Table 7, control club head 1 and control club head 2 show moderate levels of porosity in the lower half of the compound layer, 15% and 13% respectively. Exemplary club head 1 and exemplary club head 2 show very low levels of porosity in the lower half of the compound layer - 1% and <1%, which are significantly lower than the porosity of the lower half of the compound layer of control club head 1 and control club head 2. The porosity within the lower half of the compound layer creates gaps that allow microcracks formed at the surface to extend deeper into the material. Due to the similar high porosity seen in all tested club heads, microcracks are expected to form at the surface, but there is no significant effect on the strength of the coating, and the microcracks are not clearly visible to the user. The extremely low porosity of exemplary club head 1 and exemplary club head 2 results in a more resilient compound layer that resists surface deformation and prevents the formation of deep cracks.

[0146] Each sample was graded based on the degree of porosity exhibited within the compound layer, hereinafter referred to as the "oxidized loose layer grade" or "compound layer grade". Referring to Table 1, grades 1, 2, and 3 are considered to be within an acceptable porosity range. Grades 4 and 5 are considered to contain too many pores to reliably prevent unwanted surface deformation. Specifically, grades 1 and 2 describe a dense compound layer with few to no micro-pores on the surface, and the micro-pores allow micro-cracks to propagate or deepen. Grade 3 refers to a dense compound layer with micro-pores that gradually decrease from the upper layer into the material. Grades 4 and 5 describe a compound layer in which more than 2 / 3 of the compound layer is occupied by micro-pores and results in visible cracks at the arm length. As shown in Table 7 above, both control club head 1 and control club head 2 received a failed grade 4 compound layer, while exemplary club head 1 and exemplary club head 2 received an acceptable grade 3 compound layer. Thus, the traditional QPQ method cannot provide a coating for the material that contains an acceptable level of porosity. The QPQ method described herein produces a material coating that falls within an acceptable porosity level while including a desired hardened surface, providing the user with the elasticity needed to prevent surface deformation when bending.

[0147] Example III: Comparison of Flexibility and Surface Deformation Exhibited in Coatings Formed by the QPQ Method Described herein and the Traditional QPQ Method

[0148] Example III discusses the occurrence of significant visible surface deformation caused by stress on club heads treated with the QPQ method described herein. Specifically, Example 5 considers test data related to bending the hosel to adjust the face angle and club head angle and forming visible cracks in the bending region.

[0149] Samples of a single exemplary embodiment of a golf club head having a one-piece hosel structure made of 8620 steel alloy and receiving post-manufacture QPQ treatment are described herein (hereinafter referred to as "exemplary club head"), as described in the steps detailed above and in Figure 1 the steps described. Specifically, the exemplary golf club head was treated using the steps detailed in Table 3 of Example I above.

[0150] When the club head hosel is forced to bend after manufacture, visible scarring is produced at the bending site due to material deformation. The amount of surface deformation of the material after bending was analyzed and recorded according to a qualitative feedback scale. Eighteen exemplary club heads were forced to bend from a middle starting position at the hosel to an extent ranging between 3° and 5°. The upright and flat club head adjustments and open and closed face adjustments of the exemplary club heads were measured in this way.

[0151] Table 8 details the degree of attempted bending and the resulting level of surface deformation.

[0152]

[0153]

[0154] Table 8: Degree of bending at the visible demarcation point at the arm length.

[0155] The values recorded in the table indicate the change in face angle achieved before surface deformation becomes substantially visible at the arm length. Minor variations in the degree of bending are due to human error during the bending process and are generally negligible as the bending of the face angle and club head angle on post-manufactured club heads may be imprecise. As shown in Table 8, the exemplary club heads are all capable of being bent to a satisfactory degree greater than 3 degrees without any easily noticeable signs of surface deformation at the arm length. The exemplary club heads remain significantly unaffected by the applied force while maintaining the ability to be successfully bent to the desired degree without failure.

[0156] Example IV: Comparison of Surfaces

[0157] Example IV provides a qualitative comparison (i.e., crack development and surface characteristics) illustrating the effect of applying the QPQ method described herein on crack development and surface characteristics. Specifically, Example IV provides a comparison of images taken after the ferrule is bent, which depicts surface deformation in the ferrule region.

[0158] For exemplary club heads treated with the QPQ method described herein and control club heads that received conventional QPQ treatment, the visibility, occurrence rate, and size of cracks were observed and qualitatively analyzed. The exemplary club heads treated with the QPQ method described herein (hereinafter referred to as "exemplary club heads") include a one-piece ferrule structure made of 8620 steel alloy and receiving post-manufacturing QPQ treatment, as described in the steps above and in Figure 1 the steps described in detail. Specifically, the exemplary golf club heads were treated using the steps summarized in Table 3 of Example I above.

[0159] The degree of cracking seen on the surface of the exemplary club heads was compared with the degree of cracking of similar golf club heads (hereinafter referred to as "control club heads") that received conventional QPQ treatment. The conventional QPQ treatment consisted of the steps described in Table 2 of Example I above. In Figures 5A - 5G images of the surface deformation exhibited by the exemplary club heads after ferrule bending are shown. In Figure 6A - Figure 6G, images of the surface deformation exhibited by the control club heads after similar ferrule bending are shown.

[0160] Figure 5A (Exemplary club head) and Figure 6A (Control club head) show the ferrule region as observed by the naked eye (without post - treatment effects or magnification), clearly illustrating the differences between them in terms of the degree of surface deformation experienced. When observed at arm's length, the exemplary club head shows very little surface deformation, as Figure 5A shown. Specifically, there is a slightly demarcated appearance in the ferrule of the exemplary club head; however, the cracking appears to be shallow (i.e., closer to the visual range of arm's length) and may have little to no effect on the performance or durability of the club head. The ferrule of the exemplary club head does not have deep or substantial cracks that encircle the ferrule. Deep or substantial cracks encircling the ferrule are the case for the control club head. The slight surface deformation present in the ferrule of the exemplary club head is not easily observable at arm's length and requires careful inspection to identify. In contrast, Figure 6A shows significant surface deformation. The two lines of white paint were applied for testing purposes and can be ignored. The cracks in the ferrule region of the control club head appear to be obvious. Specifically, two cracks are particularly highly visible and have a deep appearance, while also encircling a large distance around the ferrule, thus casting doubt on the durability and resilience of the control club head.

[0161] Figure 5B (Exemplary club head) and Figure 6B (Control club head) depict Figure 5A and Figure 6A magnified images of the same ferrule region as shown in Figure 5B and Figure 6B , including special lighting that causes the surface deformation to fluoresce. When comparing Figure 5B and Figure 6B , when quantified by occurrence rate, length, and width, it is immediately apparent that the control club head has experienced a greater level of cracking. The exemplary club head shows very little crack fluorescence, indicating a flat surface with no substantial surface deformation. Figure 6B The cracks found in the control club head in are significant and greatly affect the appearance of the ferrule after bending. These substantial cracks affect the integrity of the coating and the user's confidence in the durability of the club head. Again, due to the non - uniform nitride layer, first oxide layer, second oxide layer (see Example 2).

[0162] Figure 5C (Exemplary club head) and Figure 6C (Control club head) are micrographs magnified 100 times, depicting the most severe cracking observed in a cross - sectional slide of the ferrule region after bending. In Figure 5CThe cracks seen in [exemplary club head] are clear and uniform, and although the crack on the left side is quite deep, it is clear from the shallow crack on the right side that the presence of deep cracks is rare. In contrast, in Figure 6C the cracks seen look jagged and rough, indicating the presence of more impurities deeper below the surface. Due to the higher incidence of deep cracks on the surface, both cracks are deep. It can also be observed that the outer surface is smoother and more uniform in the exemplary club head, while it is more uneven in the control club head. Finally, the cracks in the control club head greatly affect the surface level, which can be seen from the height difference between the surfaces immediately to the right and left of each crack, showing the instability of the compound layer, resulting in displacement that may cause further surface deformation and loss of coating and material integrity.

[0163] Figure 5D (exemplary club head) and Figure 6D (control club head) are micrographs collected after bending. These micrographs illustrate the coverage and depth of the compound layer. Immediately apparent is that the exemplary club head includes a significantly smoother and more uniform nitride layer 130 (white line) and outer surface. This uniformity promotes a stronger bond of the accompanying oxide layer and provides a harder surface that is visually more appealing and resistant to surface deformation. The thickness or depth of the compound layer in the control club head is variable throughout the image, resulting in variability in the protection provided by the QPQ process to the underlying surface in terms of hardness and strength. The surface of the control club head includes more than one pit that causes stress concentration (rather than evenly dispersing stress over a smooth surface). These pits cause cracks to form at the surface. Then, due to the porosity and defects in each individual layer that makes up the compound layer, the cracks are more likely to extend deeper into the compound layer.

[0164] Compared to the base material treated by the conventional QPQ process, when the base material is treated by the QPQ process described herein, the compound layer and each individual layer (nitride layer and oxide layer) that makes up the compound layer appear significantly smoother and more uniform, with fewer impurities. When compared to the surface treated by the conventional QPQ process, when the QPQ treatment described herein is applied to the material surface, the incidence and severity of cracks visible to the naked eye are greatly reduced when observed at the arm's length or in the magnified image.

[0165] Example V: Comparison of surface hardness between the coating formed by the QPQ process described herein and the coating formed by the conventional QPQ process

[0166] Example V provides a comparison of hardness measurements recorded for the coated surfaces of processed golf club heads. Two samples of a single exemplary embodiment of a golf club head having a one-piece ferrule structure made of 8620 steel alloy and receiving post-manufacture QPQ treatment (hereinafter referred to as "Exemplary Club Head 1" and "Exemplary Club Head 2") are described herein, as described in the steps detailed above and in Figure 1 as described in the steps detailed in

[0167] Specifically, the exemplary golf club heads are processed using the steps detailed in Table 3 of Example I above.

[0168]

[0169] Table 9: Degree of Bending at Visual Demarcation Point

[0170]

[0171] Table 10: Degree of Bending at Visual Demarcation Point

[0172] Referring to Tables 9 and 10 above, for each of the control club head samples and the exemplary club head samples, the hardness of the QPQ coating is analyzed according to the HRC Rockwell Scale. Data is collected from five readings at different locations on the surface and averaged to determine the average hardness across the surface. When compared to Control Club Head 1 and Control Club Head 2, the hardness of Exemplary Club Head 1 and Exemplary Club Head 2 is significantly greater. Specifically, the hardness of the coatings formed on Exemplary Club Head 1 and Exemplary Club Head 2 by the QPQ method described herein is 27% greater than the hardness of the coatings formed on Control Club Head 1 and Control Club Head 2 by the traditional QPQ method.

[0173] The hardness values recorded in each of the five readings can indicate the uniformity of the hardness across the surface. When compared to the control club heads treated with the traditional QPQ method, in the exemplary club heads treated with the QPQ method described herein, the range of the hardness values collected in the five readings is reduced by 36.7% - 54.5%. On average, the QPQ method described herein reduces the variation in the surface hardness values measured in Exemplary Club Head 1 and Exemplary Club Head 2 by more than 46%.

[0174] It was found that the maximum deviation of the average value was significantly lower in the exemplary clubhead 1 and exemplary clubhead 2 than in the control clubhead 1 and control clubhead 2. In the exemplary clubhead 1 and exemplary clubhead 2, the hardness readings deviated from the average value by 1.85% - 2.25% and 1.59% - 1.72% respectively. In the control clubhead 1 and control clubhead 2, the hardness readings deviated from the average value by 4.74% - 4.94% and 4.96% - 5.95% respectively. The improvement in hardness and hardness uniformity improves the wear resistance of the outer surface of the golf clubhead, while still allowing the core 110 to remain softer and more ductile.

[0175] Replacing one or more of the claimed elements constitutes reconstruction rather than repair. Additionally, benefits, other advantages, and solutions to problems have been described with respect to specific embodiments. However, a benefit, an advantage, a solution to a problem, and any element or elements that may cause any benefit, advantage, or solution to occur or become more apparent should not be construed as a critical, essential, or necessary feature or element of any claim or all claims, unless such benefit, advantage, solution, or element is expressly recited in those claims.

[0176] Since the rules of golf may change from time to time (e.g., golf standard organizations and / or governing bodies such as the United States Golf Association (USGA), the Royal and Ancient Golf Club of St Andrews (R&A), etc. may adopt new regulations, or may cancel or modify old rules), golf equipment related to the devices, methods, and manufactured articles described herein may or may not comply with the rules of golf at any given time. Accordingly, golf equipment related to the devices, methods, and manufactured articles described herein may be advertised, offered for sale, and / or sold as compliant or non-compliant golf equipment. The devices, methods, and manufactured articles described herein are not limited in this regard.

[0177] Although the above examples may be described in connection with iron-type golf clubs, the devices, methods, and manufactured articles described herein may be applicable to other types of golf clubs, such as driver wood-type golf clubs, fairway wood-type golf clubs, hybrid golf clubs, iron-type golf clubs, wedge-type golf clubs, or putter-type golf clubs. Alternatively, the devices, methods, and manufactured articles described herein may be applicable to other types of sports equipment, such as hockey sticks, tennis rackets, fishing rods, ski poles, etc.

[0178] In addition, if the embodiments and / or limitations disclosed herein: (1) are not expressly claimed in the claims; and (2) are equivalents or potential equivalents of the recited elements and / or limitations in the claims under the doctrine of equivalents, then these embodiments and limitations are not dedicated to the public under the doctrine of dedication.

[0179] The various features and advantages of the present disclosure are set forth in the following items and claims.

[0180] Item 1. A method for treating a golf club head, the method comprising: aging a nitriding salt in a first furnace for a predetermined amount of time; sandblasting an outer surface of the golf club head; placing a holding fixture in a second furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time; moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the first furnace for a predetermined amount of time, wherein a nitride layer is formed on the outer surface; reducing the temperature of the first furnace to a predetermined temperature for a predetermined amount of time, wherein a first oxide layer grows on top of the nitride layer; removing the holding fixture from the first furnace, cooling the golf club head to a predetermined temperature, cleaning the golf club head, and unloading the golf club head from the holding fixture; sandblasting the outer surface of the golf club head; placing the holding fixture in the second furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time; moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the first furnace for a predetermined amount of time, wherein a second oxide layer grows on the first oxide layer; removing the holding fixture from the first furnace, cooling the golf club head to a predetermined temperature, and cleaning the golf club head; and sandblasting the outer surface of the golf club head, wherein the nitride layer, the first oxide layer, and the second oxide layer are uniform.

[0181] Item 2. The method according to claim 1, wherein the nitriding salt has a CNO concentration between 28% and 36%.

[0182] Item 3. The method according to claim 1, wherein the sandblasting in step (b) is performed with glass beads having a grit size of 220#.

[0183] Item 4. The method according to claim 1, wherein the nitride layer has a nitride thickness between 0.00025 inches and 0.00060 inches.

[0184] Item 5. The method according to claim 4, wherein the nitride layer has a maximum nitride thickness and a minimum nitride thickness; wherein the maximum nitride thickness is between 0.00025 inches and 0.00045 inches, and the minimum nitride thickness is between 0.00045 inches and 0.00060 inches.

[0185] Item 6. The method according to claim 5, wherein the nitride layer has a nitride uniformity of less than 1.25.

[0186] Item 7. The method according to claim 1, wherein the first oxide layer has a first oxide thickness of less than 0.000115 inches.

[0187] Item 8. The method according to claim 7, wherein the first oxide layer has a first oxide maximum thickness and a first oxide minimum thickness; wherein the first oxide maximum thickness is between 0.000075 inches and 0.000115 inches, and the first oxide minimum thickness is between 0.000050 inches and 0.000075 inches.

[0188] Item 9. The method according to claim 8, wherein the first oxide layer has a first oxide uniformity of less than 1.85.

[0189] Item 10. The method according to claim 1, wherein the second oxide layer has a second oxide thickness of less than 0.000115 inches.

[0190] Item 11. The method according to claim 10, wherein the second oxide layer has a second oxide maximum thickness and a second oxide minimum thickness; wherein the second oxide maximum thickness is between 0.000075 inches and 0.000115 inches, and the second oxide minimum thickness is between 0.000050 inches and 0.000075 inches.

[0191] Item 12. The method according to claim 11, wherein the second oxide layer has a first oxide uniformity of less than 1.65.

[0192] Item 13. A golf club head, comprising: a body having a top rail opposite a bottom and a toe opposite a heel; a ferrule coupled to the club body and having a first end near the heel and a second end opposite the first end; an outer surface including a QPQ finish; wherein the QPQ finish includes a nitride layer, a first oxide layer, and a second oxide layer; wherein the outer surface includes a Class 3 QPQ finish; wherein the nitride layer has a nitride uniformity between 1.00 and 1.25; wherein the first oxide layer has a first oxide uniformity between 1.00 and 1.25; and wherein the second oxide layer has a second oxide uniformity between 1.00 and 1.25.

[0193] Item 14. The golf club head according to claim 13, wherein the QPQ finish has a hardness between 55HRC and 65HRC.

[0194] Item 15. The golf club head according to claim 13, wherein the nitride layer has a nitride thickness between 0.00025 inches and 0.00060 inches.

[0195] Item 16. The golf club head according to claim 13, wherein the nitride layer has a maximum nitride thickness and a minimum nitride thickness; and wherein the maximum nitride thickness is between 0.00025 inches and 0.00045 inches, and the minimum nitride thickness is between 0.00045 inches and 0.00060 inches.

[0196] Item 17. The golf club head according to claim 13, wherein the first oxide layer has a first oxide thickness less than 0.000115 inches.

[0197] Item 18. The golf club head according to claim 13, wherein the first oxide layer has a maximum first oxide thickness and a minimum first oxide thickness; wherein the maximum first oxide thickness is between 0.000075 inches and 0.000115 inches, and the minimum first oxide thickness is between 0.000050 inches and 0.000075 inches.

[0198] Item 19. The golf club head according to claim 13, wherein the second oxide layer has a second oxide thickness less than 0.000115 inches.

[0199] Item 20. The golf club head according to claim 13, wherein the second oxide layer has a maximum second oxide thickness and a minimum second oxide thickness; wherein the maximum second oxide thickness is between 0.000075 inches and 0.000115 inches, and the minimum second oxide thickness is between 0.000050 inches and 0.000075 inches.

Claims

1. A method for processing a golf club head, the method comprising: (a) aging a nitriding salt in a first furnace for a predetermined amount of time; (b) sandblasting an outer surface of the golf club head; (c) placing a holding fixture in a second furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time; (d) moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the first furnace for a predetermined amount of time, wherein a nitride layer is formed on the outer surface; (e) reducing the temperature of the first furnace to a predetermined temperature for a predetermined amount of time, wherein a first oxide layer grows on top of the nitride layer; (f) removing the holding fixture from the first furnace, cooling the golf club head to a predetermined temperature, cleaning the golf club head, and unloading the golf club head from the holding fixture; (g) sandblasting the outer surface of the golf club head; (h) placing the holding fixture in the second furnace and heating the second furnace to a predetermined temperature for a predetermined amount of time; (i) moving the holding fixture from the second furnace to the first furnace and allowing the holding fixture to remain in the first furnace for a predetermined amount of time, wherein a second oxide layer grows on the first oxide layer; (j) removing the holding fixture from the first furnace, cooling the golf club head to a predetermined temperature, and cleaning the golf club head; and (k) sandblasting the outer surface of the golf club head, wherein the nitride layer, the first oxide layer, and the second oxide layer are uniform.

2. The method according to claim 1, wherein the nitriding salt has a CNO concentration between 28% and 36%.

3. The method according to claim 1, wherein the sandblasting in step (b) is performed with glass beads of 220# grit size.

4. The method according to claim 1, wherein the nitride layer has a nitride thickness between 0.00025 inches and 0.00060 inches.

5. The method according to claim 4, wherein the nitride layer has a maximum nitride thickness and a minimum nitride thickness; wherein the maximum nitride thickness is between 0.00025 inches and 0.00045 inches, and the minimum nitride thickness is between 0.00045 inches and 0.00060 inches.

6. The method according to claim 5, wherein the nitride layer has a nitride uniformity of less than 1.

25.

7. The method according to claim 1, wherein the first oxide layer has a first oxide thickness of less than 0.000115 inches.

8. The method according to claim 7, wherein the first oxide layer has a maximum first oxide thickness and a minimum first oxide thickness; wherein the maximum first oxide thickness is between 0.000075 inches and 0.000115 inches, and the minimum first oxide thickness is between 0.000050 inches and 0.000075 inches.

9. The method according to claim 8, wherein the first oxide layer has a first oxide uniformity of less than 1.

85.

10. The method according to claim 1, wherein the second oxide layer has a second oxide thickness of less than 0.000115 inches.

11. The method according to claim 10, wherein the second oxide layer has a second oxide maximum thickness and a second oxide minimum thickness; wherein the second oxide maximum thickness is between 0.000075 inches and 0.000115 inches, and the second oxide minimum thickness is between 0.000050 inches and 0.000075 inches.

12. The method according to claim 11, wherein the second oxide layer has a first oxide uniformity of less than 1.

65.

13. A golf club head, comprising: a body having a top rail opposite a bottom and a toe opposite a heel; a ferrule coupled to the club body and having a first end near the heel and a second end opposite the first end; an outer surface including a QPQ finish; wherein the QPQ finish includes a nitride layer, a first oxide layer, and a second oxide layer; wherein the outer surface includes a Class 3 QPQ finish; wherein the nitride layer has a nitride uniformity between 1.00 and 1.25; wherein the first oxide layer has a first oxide uniformity between 1.00 and 1.25; and wherein the second oxide layer has a second oxide uniformity between 1.00 and 1.

25.

14. The golf club head according to claim 13, wherein the QPQ finish has a hardness between 55 HRC and 65 HRC.

15. The golf club head according to claim 13, wherein the nitride layer has a nitride thickness between 0.00025 inches and 0.00060 inches.

16. The golf club head according to claim 13, wherein the nitride layer has a nitride maximum thickness and a nitride minimum thickness; and wherein the nitride maximum thickness is between 0.00025 inches and 0.00045 inches, and the nitride minimum thickness is between 0.00045 inches and 0.00060 inches.

17. The golf club head according to claim 13, wherein the first oxide layer has a first oxide thickness of less than 0.000115 inches.

18. The golf club head according to claim 13, wherein the first oxide layer has a first oxide maximum thickness and a first oxide minimum thickness; wherein the first oxide maximum thickness is between 0.000075 inches and 0.000115 inches, and the first oxide minimum thickness is between 0.000050 inches and 0.000075 inches.

19. The golf club head according to claim 13, wherein the second oxide layer has a second oxide thickness of less than 0.000115 inches.

20. The golf club head according to claim 13, wherein the second oxide layer has a second oxide maximum thickness and a second oxide minimum thickness; wherein the second oxide maximum thickness is between 0.000075 inches and 0.000115 inches, and the second oxide minimum thickness is between 0.000050 inches and 0.000075 inches.

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