Coating layer of hard alloy and machine article having coating layer of hard alloy on substrate surface

Abstract

[Solution] Provided is a coating layer containing a hard phase, a binder phase, no more than 2.0 area% of voids, and an abnormal phase having an area ratio of 10.0 area% or less. Examples of machine components with a coating layer of this hard alloy on the surface thereof are a cutting tool, a machining tool, and a coating application device.

Description

Hard alloy coating layer and mechanical article having said hard alloy coating layer on the surface of a substrate

[0001] The present invention relates to a hard alloy coating layer and a mechanical article having the hard alloy coating layer on a substrate surface. This application claims priority from Japanese Patent Application No. 2023-222105, filed on December 28, 2023. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] Powder metallurgy is a method for producing machine parts using hard alloys. In this method, hard alloy powder is pressure-molded into a shape with a cutting allowance for the desired machine part, sintered, and then the sintered body is processed by grinding, electric discharge machining, etc. to obtain the desired shape of the machine part.

[0003] In this method, because a cutting allowance is provided, there are portions that do not become the intended mechanical part, to varying degrees, resulting in a waste of expensive raw material powder containing W, Co, and Ni. Also, hard alloys are used in portions that do not actually require the use of hard alloys, resulting in a waste of expensive raw material powder. Therefore, several proposals have been made in light of this situation.

[0004] For example, Patent Document 1 describes a method for producing a sintered body of a complex shape using an additive manufacturing method, which is said to be capable of obtaining a sintered body of a shape very close to the desired shape and to reduce the amount of raw material powder used.

[0005] Furthermore, for example, Patent Document 2 describes a cutting tool that uses a hard alloy only in necessary portions, and a composite mechanical component that has an intermediate layer between a cemented carbide part made of a WC-Co based cemented carbide and a mechanical component that contains 50 mass % or more of Ni and Co in total, and it is said that the composite mechanical component has excellent high-temperature strength and can suppress the occurrence of cracking and peeling.

[0006] JP 2018-83959 A International Patent Publication No. 2019 / 069701

[0007] The present invention aims to provide a hard alloy coating layer and a mechanical component having the coating layer formed thereon. The coating layer and method make it possible to obtain a coating layer having a sound alloy structure and high durability, and a mechanical component having the coating layer formed thereon, without wasting expensive W, Co, or Ni powders.

[0008] The hard alloy coating layer according to an embodiment of the present invention has a hard phase and a binder phase, the area ratio of abnormal phase is 10.0% or less, and the area ratio of voids is 2.0% or less.

[0009] The hard alloy coating layer may satisfy at least one of the following (1) and (2).

[0010] (1) The Vickers hardness is 1200 Hv or more, and (2) The average equivalent circle diameter (D50) of the hard phase is 0.3 to 10.0 μm.

[0011] Moreover, the machine part according to the embodiment of the present invention has a coating layer of the above-mentioned hard alloy on its surface, and examples thereof include cutting tools, which are tools, cutting tools, coating devices, and die rolls.

[0012] The hard alloy coating layer has a low area ratio of abnormal phases and voids, and therefore has a sound alloy structure (defined below), increasing the durability of the mechanical component. Furthermore, since the mechanical component has the hard alloy coating layer only on its surface (for example, in areas of the mechanical component where hardness and mechanical strength are more required), the use of raw material powders containing expensive W, Co, and Ni can be reduced.

[0013] 1 is a schematic diagram of an example of an apparatus for manufacturing a mechanical component according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of an example of a die cutter, which is a mechanical component (cutting tool) on which a surface coating layer of an example is formed.

[0014] The present inventors first studied the disclosures of Patent Documents 1 and 2 to find a way to improve the durability of cutting edges (cutting edge shaped portions) and forming grooves using a small amount of raw material powder containing expensive W, Co, and Ni in, for example, cutting tools, cutting tools, coating devices, and die rolls having forming grooves, and confirmed the following points.

[0015] (1) Regarding the additive manufacturing method described in Patent Document 1, many voids exist within the granulated powder, and large voids also exist between the granulated powder particles. Furthermore, because pressure molding using a press or other method is not performed, voids (cavities) remain in the sintered body heated by a laser. One method for suppressing voids in the sintered body is to increase the laser output and melt the granulated powder at a high temperature. However, when granulated powder of a hard alloy containing a hard phase and a binder phase is melted at a high temperature, the high-melting-point hard phase melts, generating an embrittlement phase or a hard phase with grain growth. This prevents the formation of a sound alloy structure (defined below), resulting in a decrease in the hardness and strength of the sintered body. Furthermore, this additive manufacturing method is difficult to use for manufacturing large machine parts.

[0016] (2) Regarding the cutting tool described in Patent Document 2, in which a hard alloy is used only in necessary portions, Patent Document 2 describes that cracking and peeling are suppressed by forming an intermediate layer in which the components of the hard alloy and the mechanical part are mixed. However, since the hard alloy, which is composed of a high-melting-point hard phase and a low-melting-point binder phase, is melted by direct irradiation with a heat source, the intermediate layer does not have a sound alloy structure. Furthermore, the mechanical part is limited to Ni, Co, or an alloy containing Ni or Co in a total of 50 mass% or more, making it difficult to manufacture a hard alloy composite structure in which steel is used as the mechanical part.

[0017] Next, the following known techniques were examined, and the following findings were reached: (3) Wire Directional Energy Deposition (DED) Method The wire DED method is a method in which a filler metal in wire form is fed, melted by a laser, coated on a mechanical component, and finished into a desired shape. However, because it is difficult to control the temperature of the filler metal when heating with a laser, when the filler metal is a hard alloy, the hard phase also melts, resulting in the formation of an embrittlement phase or a hard phase with abnormal grain growth in the coating layer, and thus reducing the hardness and strength of the mechanical component on which the coating layer is provided.

[0018] (4) Overlay welding Overlay welding is a process in which both the surface of a machine part and the tip of a wire-shaped filler metal are melted by a heat source to form a molten pool on the surface of the machine part, and the filler metal is fed into the molten pool from a direction different from the heat source to form the surface of the machine part with the filler metal. However, in this overlay welding, if a hard alloy is used as the filler metal, the coating layer will not have a sound alloy structure.

[0019] Based on this understanding, the inventors of the present invention conducted further research and found that if the filler metal is formed in a rod shape rather than a wire shape, and is heated to a temperature that softens the filler metal without melting it using a preheating section such as electrical heating, and the machine part is fed into a molten pool created by a heat source provided separately from the preheating section such as a laser, electron beam, plasma, or arc, and the filler metal is heated in the molten pool without melting the hard phase of the hard alloy filler metal, a coating layer formed on the machine part using the hard alloy filler metal will have a sound alloy structure. The present invention is based on this finding.

[0020] The wire shape refers to a wire rod that is easily bent so that it can be fed from a cylindrical body such as a bobbin, whereas the rod shape refers to a wire rod that is highly rigid and difficult to bend, making it difficult to feed from the cylindrical body. The rod shape may have any cross section, such as a circle, an ellipse, or a rectangle.

[0021] Hereinafter, a hard alloy coating layer for coating and a mechanical part having the hard alloy coating layer formed thereon according to an embodiment of the present invention will be described. In this specification and claims, when a numerical range is expressed as "L to M" (L and M are both numerical values), this is synonymous with "not less than L and not more than M", and the range includes an upper limit (M) and a lower limit (L). When a unit is stated only for the upper limit, the upper limit (M) and the lower limit (L) have the same unit.

[0022] "Hard alloy" as used in the claims and this specification refers to an alloy (super hard alloy) based on W carbide or any of the carbides, nitrides, or carbonitrides of elements in Groups 4 to 6 of the periodic table, and further containing iron group elements such as Co, Ni, etc. Furthermore, "the appearance of the coating layer is normal" means that when the coating layer is visually inspected, there is no cracking, overlapping, humping, undercutting, or meandering.

[0023] Furthermore, the term "sound alloy structure" as used in this specification refers to a structure that does not contain (a predetermined proportion or less) phases such as embrittlement phases, low carbon phases, free carbon phases, and defects of coarse hard phases (these phases and defects are collectively referred to as abnormal phases), nor voids (not to be distinguished from voids).

[0024] 1. Hard alloy coating layer The hard alloy coating layer formed from the hard alloy will be described.

[0025] (1) Structure The hard alloy coating layer consists of a hard phase, a binder phase, a selectively present secondary hard phase, and an abnormal phase. Also, voids exist within the hard alloy coating layer.

[0026] 1) Hard Phase The hard phase is not particularly limited as long as it is used as a hard phase of a hard alloy, and may be, for example, W carbide (which may contain W carbide other than WC), a composite nitride of W and Ti, or nitride ceramics (TiN, TaN, NbN, etc.).

[0027] Although there are no particular restrictions on the average diameter of the hard phase, it is more preferable that the circle-equivalent diameter D50 (cumulative 50% diameter: median diameter) is 0.3 to 10.0 μm. When the average diameter (D50) of the hard phase satisfies this range, the coating layer has better hardness and toughness. If the average diameter exceeds 10 μm, the binder phase also becomes large, resulting in insufficient resistance to plastic deformation and increased wear, which may lead to early deterioration of sharpness when used, for example, as a coating layer for a hard alloy of a cutting tool. If the average particle size is less than 0.3 μm, the toughness against the load during cutting is insufficient, and early chipping of the cutting tool may occur. The average diameter of the hard phase is more preferably 0.5 to 3.5 μm, and even more preferably 0.6 to 1.5 μm.

[0028] Here, the cumulative 50% diameter (median diameter) refers to the circle-equivalent diameter at which the cumulative percentage is 50% when the horizontal axis is the equivalent circle diameter and the vertical axis is the cumulative percentage of the hard phase relative to the equivalent circle diameter. The number of hard phases on the larger and smaller sides of this cumulative 50% diameter is equal.

[0029] 2) Binder Phase The components and composition of the binder phase are determined according to the components of the hard phase. Examples include binder phases containing Co, Ni, and Fe as the main components.

[0030] The area ratios of the hard phase and binder phase in the coating layer are preferably 50% or more for the hard phase and 40% or less for the binder phase for the following reasons. When the area ratio of the hard phase is less than 50% or the area ratio of the binder phase is greater than 40%, the coating layer has high toughness and is superior in fracture resistance, but its wear resistance is insufficient and it is prone to early wear. Therefore, when used as a coating layer for a cutting tool, for example, cutting performance cannot be maintained for a long period of time. It is more preferable that the hard phase be 85% or less and the binder phase be 5% or more.

[0031] In order to obtain a preferable Vickers hardness (1200 HV or more) described later, the relationship between the D50 of the hard phase and the area ratio of the binder phase is preferably as follows: when the D50 of the hard phase is 0.3 to 10.0 μm, the area ratio of the binder phase is 5 to 35%; when the D50 of the hard phase is 0.5 to 3.5 μm, the area ratio of the binder phase is 7 to 30%; and when the D50 of the hard phase is 0.6 to 1.5 μm, the area ratio of the binder phase is 9 to 25%.

[0032] 3) Secondary Hard Phase Optionally added elements such as Cr, V, etc. constitute a secondary hard phase as a carbide. Since the addition of Cr, V, etc. is optional, the presence of a secondary hard phase is not essential, but when present, it is preferable that the area ratio of the secondary hard phase in the coating layer is 10% or less. This is because if the area ratio of the secondary hard phase exceeds 10%, the secondary hard phase has poor wettability with the binder phase mainly composed of Co or Ni, which makes it more likely for the hard phase and secondary hard phase to aggregate, resulting in a decrease in the bending strength and a loss of toughness of the coating layer. It is even more preferable that the area ratio of the secondary hard phase is 5% or less (it may be 0 area %).

[0033] 4) Abnormal Phase The area ratio of the abnormal phase in the coating layer is preferably 10% or less. This is because if the area ratio of the abnormal phase exceeds 10%, the probability of the abnormal phase being exposed on the cutting edge of a machine part that has been polished to a sharp edge increases. In other words, a cutting edge with exposed abnormal phase does not have the wear resistance and toughness required for a cutting edge, and such a cutting edge cannot maintain cutting performance over a long period of time. Since it is preferable that the abnormal phase does not exist, the lower limit of the area ratio of the abnormal phase is 0%.

[0034] Phases that do not fall into the categories of hard phase, binder phase, or secondary hard phase are considered to be abnormal phases. However, we will further explain defects in phases such as embrittlement phases, low carbon phases, and free carbon phases, as well as coarse hard phases, which are considered to be abnormal phases.

[0035] 4-1) Embrittlement phase The embrittlement phase is W ２ C, M ６ C is W ３ Co ３ C or W ４ Co ２ C, M １２ C is W ６ Co ６ It is composed of one or more of WC. ２ C is hard but brittle and easily broken. ６ C and M １２ C is very brittle and reduces the strength of the hard alloy coating layer.

[0036] 4-2) Low carbon phase The low carbon phase appears due to carbon deficiency or decarburization reaction during the manufacturing process. ６ C is W ３ Co ３ C, M １２ C is W ６ Co ６ The low carbon phase is composed of one or more of C. When the low carbon phase is present, the bending strength and compressive strength of the hard alloy coating layer are reduced, which is undesirable.

[0037] 4-3) Free carbon phase The free carbon phase is graphite formed due to an excessive carbon content or when carbides such as WC decompose and precipitate independently without bonding with metal elements. The free carbon phase appears due to excessive addition of carbon or carburization during the manufacturing process, and is undesirable because it reduces the flexural strength and hardness of the hard alloy coating layer.

[0038] 4-4) Coarse hard phases Coarse hard phases are those in which the coarse phase diameter of the hard phase is equal to or greater than the average phase diameter (D50) of the hard phases x 3. The presence of coarse hard phases leads to a decrease in the flexural strength of the coating layer, and in the case of mechanical parts formed with a hard alloy coating layer, they become the starting point of fracture. In addition, the presence of coarse hard phases increases the gaps between the hard phases, resulting in coarsening of the binder phase. Areas in which the binder phase has coarsened have reduced resistance to plastic deformation, which causes rapid wear and shortens the lifespan.

[0039] 5) Voids The presence of voids, or cavities, is undesirable. For example, when a machine part coated with a hard alloy is a cutting tool, a sharp edge is required at the cutting edge. However, if voids exist, they may be exposed on the cutting edge of the polished cutting tool. This is because the exposed voids cause a localized decrease in sharpness, resulting in poor cutting.

[0040] Here, the area ratio of voids is defined as follows: Area ratio of voids (%) = (area of ​​voids in hard alloy coating layer) / (area of ​​hard alloy coating layer) x 100 Since it is preferable that no voids exist in the hard alloy coating layer, the lower limit of the area ratio of voids is 0%. A method for measuring the area ratio of voids will be described later.

[0041] (2) Composition There are no particular restrictions on the composition of the hard alloy coating layer as long as it satisfies the above-mentioned structure. For example, the following can be mentioned.

[0042] 1) WC cemented carbide Co: 5.0 to 20.0 mass%, Cr: 2.0 mass% or less (including 0.0 mass%), V: 1.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. Preferably, Co: 7.0 to 10.0 mass%, Cr: 1.5 mass% or less (including 0.0 mass%), V: 0.5 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. More preferably, Co: 10.0 to 16.0 mass%, Cr: 1.0 mass% or less (including 0.0 mass%), V: 0.5 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities.

[0043] 2) WC-TiC-TaC-NbC cemented carbide Co: 5.0 to 20.0 mass%, TiC: 25.0 mass% or less (including 0.0 mass%), TaC: 20.0 mass% or less (including 0.0 mass%), NbC: 15.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. Preferably, Co: 7.0 to 10.0 mass%, TiC: 25.0 mass% or less (including 0.0 mass%), TaC: 10.0 mass% or less (including 0.0 mass%), NbC: 10.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. More preferably, Co: 10.0 to 16.0 mass%, TiC: 20.0 mass% or less (including 0.0 mass%), TaC: 10.0 mass% or less (including 0.0 mass%), NbC: 10.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities

[0044] (3) Vickers Hardness The Vickers hardness of the hard alloy coating layer is preferably 1200 Hv or higher. If the Vickers hardness is less than 1200 Hv, the hard alloy coating layer will have poor wear resistance and be prone to wear. There is no particular upper limit to the Vickers hardness, but according to an example of the manufacturing method described below, the upper limit is approximately 1800 Hv. A Vickers hardness of 1300 to 1800 Hv is more preferably, and 1400 to 1700 HV is even more preferably. Here, the Vickers hardness is measured under a load of 294 N according to the method specified in ISO 6507 or ASTM E385.

[0045] (4) Method for Identifying Each Phase and Measuring the Area Ratio Thereof After identifying the binder phase, secondary hard phase, and hard phase, the area ratio of each of the phases is measured as follows.

[0046] 1) Observation by EDS and EBSD Any cross section or surface of the cemented carbide coating layer is processed to remove any minute irregularities so as to be smooth and not interfere with measurement by an electron backscatter diffraction (EBSD) device. Observation fields are set on the processed surface and observed. The size and number of observation fields may be appropriately set depending on the specifications of the EBSD device used. Multiple observation fields (e.g., five or more fields) are set at any positions so that the total field size is, for example, 24 μm (vertical) × 72 μm (horizontal).

[0047] The sample is then observed using a field emission scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and an EBSD measurement device (OIM Data Collection, manufactured by AMETEK). Observation conditions can be determined based on the specifications of the device used. When using the exemplified measurement device, observation is performed at an acceleration voltage of 20 kV, and EBSD patterns and EDS data are simultaneously acquired. The working distance (distance between the lower surface of the objective lens and the sample) is 15 mm, the measurement count rate is 41,000 cps, and the measurement interval is 50 nm. Measurement points (pixels) are present discretely, but the region (preferably a regular hexagon) extending to the middle between adjacent measurement points is represented by the measurement results of that measurement point. When there is an orientation difference of 5 degrees or more between adjacent measurement points, the region extending to the middle is defined as a crystal grain. However, a measurement point that has an orientation difference of 5 degrees or more from all of its adjacent measurement points, or that exists alone with no adjacent measurement points, is not treated as a crystal grain, and a measurement point is treated as a group of two or more measurement points connected together.

[0048] 2) Identification of each crystal grain For example, measurement data is read into OIM Analysis ver. 7.3.1 manufactured by AMETEK, and for each crystal grain, the EDS count values ​​obtained from each measurement point inside the crystal grain corresponding to each element are averaged to obtain the EDS measurement value of each element in each crystal grain, and the composition of each crystal grain is derived from the obtained measurement value. The details are as follows.

[0049] First, the EDS count values ​​of all elements, W, Co, Ni, Fe, Cr, V, Ta, Ti, Nb, and other elements, are averaged over the entire observation field, and then the EDS count values ​​of each element at each pixel inside each grain are averaged to derive the composition of each grain.

[0050] The hard phase is considered to be an aggregate of crystal grains with W as the main component and hcp crystal structure, the binder phase is considered to be an aggregate of crystal grains with Co, Ni, or Fe as the main component and fcc or hcp crystal structure, and the secondary hard phase is considered to be an aggregate of crystal grains with Cr, V, Ta, Ti, Nb, etc. as the main component, and each phase is identified. Phases that do not fall into any of the hard phase, binder phase, or secondary hard phase are considered to be abnormal phases.

[0051] 3) Measurement of the size of hard phases To identify coarse hard particles, the diameter (circle equivalent diameter) of each hard phase is measured, and the average particle size (D50) is calculated. Then, as described above, hard phases having an average diameter three times or more the average diameter (D50) are treated as coarse hard phases, and the area ratio of the coarse hard phases is measured. This measured area ratio is then added to the area ratio of the abnormal phase and subtracted from the area ratio of the hard phase. Here, when calculating the average diameter, it is preferable to measure 300 or more hard phases in order to accurately determine the average diameter.

[0052] (5) Measurement of the Area Ratio of Voids Assuming that voids are uniformly present in the hard alloy coating layer, the voids are measured as follows. A sample piece is cut out from the hard alloy coating layer and mirror-polished. An observation field of 430 μm × 600 μm is arbitrarily set on the polished sample piece, and an image is observed. The observed image is then binarized so that the voids and other areas can be distinguished.

[0053] That is, a 256-level gradation display is used, with 0 representing white and 255 representing black, with the lower limit set to 0 and the upper limit set to half the gradation having the most frequent value in the observed image. A threshold is then set using Otsu's binarization process, and the white areas are considered to be voids, and the area ratio of these white areas is measured. As is clear from this measurement method, the area ratio of voids is measured independently of the area ratios of the hard phase, binder phase, etc. that make up the hard alloy coating layer.

[0054] (6) Measurement of the average content of each component The content of each component is measured using an electron probe microanalyzer. A sample for analysis is cut out from the hard alloy coating layer, and three observation fields of 96 μm x 128 μm or more are set on the mirror-finished surface (the surface is smoothed by removing any minute irregularities so as not to interfere with the characteristic X-ray analysis using the electron probe microanalyzer). The components contained and their amounts are measured using characteristic X-rays, and the average of the measurement results is calculated as the content.

[0055] 2. Mechanical Parts Mechanical parts on which a hard alloy coating layer is formed will be described.

[0056] (1) Type and Material of Mechanical Parts There are no particular restrictions on the mechanical parts on which the hard alloy coating layer is formed, as long as they have a shape appropriate for the intended use. Examples of the shape of the mechanical parts include cutting tools (e.g., die cutters), cutting tools (e.g., end mills), and coating devices (e.g., slot dies). There are also no particular restrictions on the material of the mechanical parts, as long as they are appropriate for the intended use, and examples of the material include carbon steel, low-alloy steel, stainless steel, and WC cemented carbide.

[0057] (2) Surface Layer A hard alloy coating layer may be formed directly on the surface of the mechanical component. Alternatively, a surface layer consisting of one or more layers may be provided on the mechanical component, and a hard alloy coating layer may be formed on the surface layer. There are no particular restrictions on the composition of the surface layer, and examples of the surface layer include NCF600, NCF718, and DCoCrC, which are represented by JIS material symbols. The thickness of the surface layer depends on the application, shape, etc. of the mechanical component, so it is difficult to discuss the thickness in a uniform manner, but examples of the thickness include 1 to 5 mm.

[0058] 3. Manufacturing Method A hard alloy coating layer and a mechanical component having the hard alloy coating layer formed thereon can be obtained by the following procedure.

[0059] (1) Manufacturing method of rod-shaped hard alloy filler metal 1) Raw material powder of hard alloy coating layer Raw material powder of filler metal corresponding to the composition of hard alloy coating layer is prepared. The raw material powder is WC powder, Cr powder, ３ C ２ Examples of the powder include VC powder, Co powder, TiC powder, TaC powder, NbC powder, TaNbC powder, TiN powder, and NbN powder.

[0060] The raw material powder preferably has an average particle size (Fisher diameter) within a predetermined range. For example, the average particle size (Fisher diameter) of WC powder is 0.5 to 1.5 μm, that of Cr powder is 0.5 to 1.5 μm, and that of Cr powder is 0.5 to 1.5 μm. ３ C ２ The Fischer diameter is measured by a sub-sieve sizer.

[0061] 2) Blending (Mixing) The raw material powders prepared in (1) above are blended to a predetermined blend composition, paraffin wax and ethanol are further added, and the blend is pulverized and mixed in a ball mill for a predetermined time to uniformly disperse the raw material powders, and then dried under reduced pressure.

[0062] 3) Press Molding The mixed powder obtained in (2) above is mixed with a thickener, a surfactant, etc., and molded by injection molding into a green material that will serve as the base for the rod shape after sintering.

[0063] 4) Sintering The green mold body obtained in 3) above is degreased by holding it at 780 to 850°C for 100 to 140 minutes with a temperature increase rate of 0.3 to 1.0°C / min, and subsequently sintered by holding it at a temperature of 1350 to 1450°C for 50 to 70 minutes with a temperature increase rate of 2 to 8°C / min in a vacuum of about 20 Pa, and then cooled to room temperature at a rate of 5 to 8°C / min in an argon gas atmosphere.

[0064] 5) HIP Treatment The sintered body is subjected to HIP treatment in an Ar gas atmosphere, where the temperature is raised to 1250-1350°C at a rate of 5-10°C / min, and the temperature is held at a pressure of 85-95 MPa for 50-70 minutes, and then the body is cooled to room temperature at a rate of 3-10°C / min. The shape of the molded body that has undergone HIP treatment, i.e., the filler metal, is, for example, a long object with a circular cross section having a diameter of 3 mm and a length of 1500 mm.

[0065] (2) Coating For example, a hard alloy coating layer is coated on a mechanical part using a molding apparatus as shown in Fig. 1. There are no restrictions on the shape of the part of the mechanical part (1) to be coated with the coating layer, and examples of the cross-sectional shape include a polygon, a semicircle, and a semi-ellipse. The angles described below are defined with the top (apex) of this cross-section as the reference line.

[0066] In the molding device shown in FIG. 1 , a rod-shaped filler metal (3) (a rod-shaped hard alloy filler metal for forming a hard alloy coating layer) is heated to a softening temperature in a preheating section (hot wire torch) (2) on a mechanical component and then fed to a molten pool on the surface of the mechanical component (1) by a feeding section (not shown). A molten pool is formed on the mechanical component (1) by heat irradiated from a heat source (4) provided separately from the preheating section. The filler metal remains softened and unmelted until it is fed into the molten pool (6). In this molten pool (6), the hard phase in the rod-shaped hard alloy filler metal (3) does not melt, and only the binder phase melts. The hard alloy then naturally cools, forming a hard alloy coating layer (5) on the surface of the mechanical component (1). The arrow in FIG. 1 indicates the direction in which the coating layer is formed. Note that the molten portion of the mechanical component and the heat-affected zone (HAZ) are not shown in FIG. 1 .

[0067] Here, in the apparatus for coating a hard alloy coating layer shown in Figure 1, the feed angle of the rod-shaped hard alloy filler (3) heated to a temperature at which it remains softened and not melted until it is fed into the molten pool (the feed angle of the filler) is preferably more than 4° and not more than 75° (more preferably 5 to 60°, even more preferably 7 to 45°, and even more preferably 10 to 35°), and the incident angle of the heat irradiated from the heat source (4) is 3 to 60° (more preferably 4 to 40°, and even more preferably 5 to 35°), and the feed angle is greater than the incident angle.

[0068] The reason why the above feed angle is preferable is that if the feed angle exceeds 75°, the laser spot is likely to interfere with the hot wire torch used as a preheating section, and the resulting thermal effect causes the hot wire torch to become extremely hot, which is undesirable. On the other hand, if the feed angle is less than 5°, the laser spot is likely to spread in the welding direction, resulting in the formation of an excessive molten pool and, as a result, abnormalities such as meandering of the weld bead are likely to occur.

[0069] In the apparatus for applying a hard alloy coating layer shown in FIG. 1, both the preheating section (hot wire torch) (2) and the heat source (4) are provided on the front surface where the coating layer is to be formed, but at least one of the preheating section (hot wire torch) (2) and the heat source (4) may be provided on the rear surface where the coating layer is to be formed or on a side surface where the coating layer is not to be formed.

[0070] Here, the softening temperature of the rod-shaped hard alloy filler material (3) means that the surface temperature of the rod-shaped hard alloy filler material (when W carbide is the base alloy) measured with a radiation thermometer is 1200 to 2000 ° C (preferably 1200 to 1700 ° C).

[0071] In this way, by softening the rod-shaped hard alloy filler metal by the preheating section (2), the hard phase of the rod-shaped hard alloy filler metal does not melt in the molten pool in which the mechanical component is melted by heat applied to the mechanical component from a heat source (4) provided separately from the preheating section, and only the bonding phase melts, forming a coating layer.

[0072] An example of the heating means for the preheating section 2 is an electric heating device. The heat source 4 provided separately from the preheating section is not limited as long as it applies heat, and examples thereof include a laser, electron beam, plasma, or arc source.

[0073] The rod-shaped hard alloy filler material (3) remains in a softened state without melting until it is fed into the molten pool, meaning that the filler material remains in a softened state even when exposed to the irradiated heat, in addition to when it is not exposed to the heat for forming the molten pool, and also means that the filler material remains in a softened state even when the heat of the molten pool is transmitted to the filler material by conduction or radiation, i.e., the surface temperature of the rod-shaped hard alloy filler material (when W carbide is the base alloy) is in the range of 1200 to 2000°C.

[0074] The thickness of the hard alloy coating layer varies depending on the application of the mechanical part to which the hard alloy coating layer is applied, but in the case of a die cutter, which is a cutting tool, it is preferable to form it so that it is about 5 mm thick after the subsequent polishing process.

[0075] (7) Post-treatment (polishing) The surface roughness of the hard alloy coating layer is preferably a predetermined value or less. The allowable surface roughness depends on the application of the machine part, but for example, for a die cutter, which is a cutting tool, Rz according to ISO 4287-1997 is preferably 0.8 μm or less, and polishing treatment is performed to achieve this surface roughness. For example, the polishing treatment can be performed by using different grinding stones to perform rough processing and finish processing.

[0076] The Vickers hardness (HV) of the coating layer is determined by the grain size of the W carbide and the area ratio of the binder phase, and it is necessary to devise manufacturing conditions to obtain a coating layer with a predetermined Vickers hardness. ３ C ２and the like, and sintering is performed at an appropriate processing temperature using a W carbide growth suppressor material, and the Fischer diameter of the WC powder used as the raw material is 0.3 to 0.8 μm and the area ratio of the binder phase is 5 to 30%, the Fischer diameter of the WC powder is 0.3 to 1.0 μm and the area ratio of the binder phase is 7 to 35%, or the Fischer diameter of the WC powder used as the raw material is 0.3 to 1.5 μm and the area ratio of the binder phase is 9 to 25%, then the Vickers hardness will be 1200 HV or more.

[0077] The above description includes the features appended below. (Appendix 1) A hard alloy coating layer having a hard phase and a binder phase, characterized in that the area ratio of abnormal phases is 10.0% or less, and the area ratio of voids is 2.0% or less. (Appendix 2) A hard alloy coating layer according to Appendix 1, characterized in that the hard phase has an average circle equivalent diameter (D50) of 0.3 to 10.0 μm. (Appendix 3) A hard alloy coating layer according to Appendix 1 or 2, characterized in that it has a Vickers hardness of 1200 Hv or more. (Appendix 4) A hard alloy coating layer according to Appendix 1 or 2, characterized in that it has a Vickers hardness of 1300 to 1800 HV. (Appendix 5) A hard alloy coating layer according to Appendix 1 or 2, characterized in that it has a Vickers hardness of 1400 to 1700 HV. (Appendix 6) A machine component having a substrate and a coating layer of the hard alloy according to any one of Appendices 1 to 5 on the surface of the substrate. (Appendix 7) A cutting tool having a substrate and a coating layer of the hard alloy according to any one of Appendices 1 to 5 on the surface of the substrate. (Appendix 8) A cutting tool having a substrate and a coating layer of the hard alloy according to any one of Appendices 1 to 5 on the surface of the substrate. (Appendix 9) A coating device having a substrate and a coating layer of the hard alloy according to any one of Appendices 1 to 5 on the surface of the substrate. (Appendix 10) A machine component according to Appendices 6, characterized in that the substrate has a surface layer consisting of one or more layers on its surface. (Appendix 11) A cutting tool according to Appendices 7, characterized in that the substrate has a surface layer consisting of one or more layers on its surface. (Appendix 12) A cutting tool according to Appendices 8, characterized in that the substrate has a surface layer consisting of one or more layers on its surface. (Appendix 13) A coating device according to Appendices 9, characterized in that the substrate has a surface layer consisting of one or more layers on its surface.

[0078] Next, an example will be described in which a hard alloy coating layer is formed on the cutting edge (12) of a die cutter consisting of a die cut roll (10) and an anvil roll (11) shown in Figure 2 and on the bearer portion (13), but the present invention is not limited to this example.

[0079] (1) Raw material powder for hard alloy coating layer (rod-shaped hard alloy filler material) As raw material powder, WC powder (average particle size (Fisher diameter: the same applies hereinafter): three types of powder with 1.2 μm, 2.3 μm, and 2.9 μm), Cr ３ C ２ Powder (average particle size: 1.4 μm), VC powder (average particle size: 1.5 μm), and Co powder (average particle size: 2.1 μm) were prepared, and these alloy powders were blended to obtain the blend composition shown in Table 1.

[0080] (2) Blending (Mixing) Next, paraffin wax and ethanol were further added, and the mixture was pulverized and mixed in a ball mill, followed by drying under reduced pressure, thereby obtaining the 10 types of mixed powders shown in Table 1.

[0081] (3) Press Molding A thickener and a surfactant were added to each of these mixed powders, and the mixture was injection molded into a long body that would serve as the base for a rod shape.

[0082] (4) Sintering Each of the long green mold bodies was degreased by holding it at 750°C for 60 minutes with a temperature increase rate of 0.5°C / min, and subsequently sintered by holding it at a temperature of 1360 to 1450°C (sintering temperature listed in Table 1) with a temperature increase rate of 1.7°C / min in a vacuum of 20 Pa for 60 minutes, and the sintered body was cooled to room temperature at 2.9°C / min in an argon gas atmosphere.

[0083] (5) HIP Treatment Next, the sintered body was subjected to HIP treatment in an Ar gas atmosphere, in which the temperature was raised to 1280°C at a temperature rising rate of 4.7°C / min and held at a pressure of 90 MPa for 60 minutes. Thereafter, the sintered body was cooled to room temperature at a cooling rate of 1.2°C / min. The shape of the 10 types of sintered molded bodies that had undergone HIP treatment was a circle with a cross section of 5 mm diameter and a long object of 1500 mm length.

[0084] (6) Coating Using the molding device shown in FIG. 1, 10 types of rod-shaped hard alloy filler metals were used to form hard alloy coating layers to a thickness of 5 mm on the cutting edge and bearer portion of the machine parts, i.e., the die cutter, to obtain 10 types of die cutters with different hard alloy coating layers (referred to as Examples 1 to 10).

[0085] During the formation, the laser output was 3.5 kW, the laser spot size was 2.0 × 6.0 mm, the filler metal feed angle was 60°, the laser incidence angle was 30°, the filler metal feed speed was 0.1 m / min, and the hot wire current was 200 A. The laser was incident on the surface of the machine part to form a molten pool, and the rod-shaped filler metal made of hard alloy was fed in a softened state without melting until it was fed into the molten pool.

[0086] (7) Polishing: A grinding process was performed using a grindstone to obtain a cutting edge with a thickness of 3 mm. The Rz was 0.8 μm. The die cutter's die cut roll and anvil roll, both made of SCM440, had a roll diameter of 150 mm and a roll width (distance between bearers) of 230 mm.

[0087] For comparison, the same raw powder material as the raw powder of the example was used except for the average particle size of the WC powder, and the laser irradiation conditions were changed as described below to obtain die cutters (referred to as Comparative Examples 1 to 5) having coating layers of five different hard alloys.

[0088] (1') Raw material powder for hard alloy coating layer As raw material powder, WC powder (average particle size: 1.5 μm, 2.9 μm, two kinds of powder), Cr ３ C ２ Powder (average particle size: 1.4 μm), VC powder (average particle size: 1.5 μm), and Co powder (average particle size: 2.1 μm) were prepared and mixed so that the hard alloy coating layer had the composition shown in Table 1.

[0089] (2') Blending (Mixing) and (3) Pressing Steps Blending (mixing) and pressing steps were carried out in the same manner as in Example.

[0090] (4') Sintering Each long molded body was degreased by holding it at 750°C for 60 minutes with a temperature increase rate of 0.5°C / min, and subsequently sintered in a vacuum of 20 Pa by holding it at a temperature of 1360°C to 1430°C (sintering temperature listed in Table 1) with a temperature increase rate of 1.7°C / min for 60 minutes. The sintered body was cooled to room temperature at 2.9°C / min in an argon gas atmosphere.

[0091] (5') HIP Treatment The same HIP treatment as in the example was carried out to obtain a sintered compact having the same shape as in the example.

[0092] (6') Coating The laser output was 6.5 kW, the laser spot size was 1.0 x 6.0 mm, the filler metal feed angle was 75°, the laser incident angle was 60°, and the rod-shaped filler metal made of hard alloy was exposed to the laser. The hot wire current was 400 A, and the filler metal feed rate was 0.15 m / min. Using the molding apparatus shown in Figure 1 as an outline, five types of compacts were used as filler metals to form hard alloy coating layers with a thickness of 5 mm on the cutting edge and bearer portion of the die cutter, which is a mechanical part, to obtain five types of die cutters with different hard alloy coating layers (referred to as Comparative Examples 1 to 5).

[0093] (7') Polishing Polishing was carried out in the same manner as in Example.

[0094] The compositions of the hard alloy coating layers of Examples 1 to 10 and Comparative Examples 1 to 5 were measured using an electron beam microanalyzer as described above, and the results are shown in Table 2. Furthermore, the area percentages of the hard phase, binder phase, abnormal phase, and voids obtained by the above-mentioned measurement method for the hard alloy coating layers formed on the die cutter are shown in Table 3. The area percentage of the secondary hard phase was 0% in both the Examples and Comparative Examples. Furthermore, the appearance of the coating layer was normal. Note that in Table 3, abnormal phases were identified by EDS and EBSD, while voids were identified by image analysis, so the identification methods for the two are different. Furthermore, because abnormal phases may contain voids, the sum of the area percentages of the hard phase, binder phase, abnormal phase, and voids may exceed 100%.

[0095]

[0096]

[0097] In Tables 1 and 2, "-" indicates that no relevant items were included.

[0098]

[0099] Next, using Examples 1 to 10 and Comparative Examples 1 to 5, a 0.2 mm thick polyester nonwoven fabric was cut. In each Example and Comparative Example, the condition of the cutting edge was checked every 10 minutes (6,000 revolutions) under the following conditions: rotation speed: 600 rpm, pressing force: 2,940 N, cutting edge protrusion: 1.5 μm. When a portion of the material being cut (nonwoven fabric) remained, the cutting edge was considered to have reached the end of its life. The cutting edge was observed, and if there was a missing portion, it was judged to be chipped; otherwise, it was judged to be worn. The results are shown in Table 4.

[0100]

[0101] As is clear from Table 4, the rotational speeds at which the die cutter reaches its end of life are all greater in Examples 1 to 10 than in Comparative Examples 1 to 5, and it is clear that the hard alloy coating layer enhances the durability of the machine part (die cutter). Furthermore, because this coating layer is present only on the cutting edge, it is possible to reduce the amount of raw material powder containing expensive W and Co used.

[0102] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0103] REFERENCE SIGNS LIST 1 Machine part 2 Preheating part (hot wire torch) 3 Rod-shaped filler metal made of hard alloy 4 Heat source provided separately from preheating part 5 Hard alloy coating layer 6 Molten pool 10 Die-cut roll 11 Anvil roll 12 Cutting edge 13 Bearer

Claims

1. A coating layer of cemented carbide, having a hard phase and a bonding phase, wherein the area ratio of abnormal phases is 10.0% or less and the area ratio of voids is 2.0% or less.

2. The coating layer of cemented carbide according to claim 1, wherein the average equivalent circle diameter (D50) of the hard phase is 0.3 to 10.0 μm.

3. The coating layer of cemented carbide according to claim 1, wherein the Vickers hardness is 1200 Hv or more.

4. A mechanical part having a substrate and a coating layer of cemented carbide according to any one of claims 1 to 3 on the surface of the substrate.

5. A cutting tool having a substrate and a coating layer of cemented carbide according to any one of claims 1 to 3 on the surface of the substrate.

6. A cutting tool having a substrate and a coating layer of cemented carbide according to any one of claims 1 to 3 on the surface of the substrate.

7. A coating device having a substrate and a coating layer of cemented carbide according to any one of claims 1 to 3 on the surface of the substrate.

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