Superhard polycrystalline diamond (PCD) bearing element attachment method and device

Abstract

Method for attaching PCD (polycrystalline diamond) bearing elements to bearing carriers in downhole drilling tools. Conventional attachment methods use brazing to directly fix PCD elements into bearing carriers, but poor braze joint quality and lack of quality control methods may lead to bearing element detachment and equipment damage. The attachment method described herein utilizes a shape memory ring that is fitted around the PCD element with a controlled gap, then heated to shrink and create a friction fit. This assembly is then positioned in the bearing carrier and welded in place. The method can be used for both axial and radial bearing applications and allows for easy inspection of the welded connection.

Description

[0001] Attorney Docket: 65DRL-511162-WO-2

[0002] SUPERHARD POLYCRYSTALLINE DIAMOND (PCD) BEARING ELEMENT ATTACHMENT

[0003] METHOD AND DEVICE

[0004] TECHNICAL FIELD

[0005] This disclosure relates to methods for attaching polycrystalline diamond (PCD) bearing elements in downhole drilling tools. More specifically, this disclosure relates to the use of shape memory alloy rings as intermediate connection components for securing PCD bearing elements within bearing carriers.

[0006] BACKGROUND

[0007] Downhole drilling tools operate in harsh environments characterized by high shear forces, high pressure, rapid vibration, abrasive drilling muds, and high temperature. Components of these drilling tools, such as but not limited to steering units and power alternators, rely on bearings to provide control and stability. PCD bearing assemblies have become increasingly utilized in these applications due to their significantly longer lifespan compared to conventional roller or plain bearings. PCD bearing assemblies can be configured in various geometries, including thrust and radial (male and female). For example, a male radial bearing can be positioned within a female radial bearing, with a thrust bearing positioned between the two to accommodate axial loads.

[0008] PCD is a synthetic diamond material produced by sintering small diamond crystals under high pressure and temperature in the presence of a metal catalyst (onto a substrate). The resulting material exhibits a combination of extreme hardness, high thermal conductivity, high strength, high toughness, and low friction, making it particularly well- suited for use in harsh downhole drilling environments.

[0009] In typical PCD bearing assemblies 10, as illustrated in FIGS. 1A, 1 B, and 1 C, small PCD inserts 12 are affixed within cavities in body 11 (often steel rings or housings or bodies). These inserts are typically secured using a brazing process, creating a brazed joint (shown and described in FIG. 2 as 14a) that is critical to the bearing’s performance when this attachment method if used. In particular, shown in FIG. 1 A is a male bearing assembly 10, shown in FIG. 1 B is a female bearing assembly 10a, and shown in FIG. 1 C is a first half of an axial bearing assembly 10'. Although, the second half of the axial bearing assembly

[0010] 65DRL-511162-WO-2 1 Attorney Docket: 65DRL-511162-WO-2

[0011] 10' is not shown, it looks similar, with the PCD inserts of the second half facing the PCD inserts 12 of the first half, but with a higher quantity of inserts.

[0012] FIG. 2 provides a diagrammatic cross-sectional view of this arrangement, in which a PCD insert 12 is shown disposed within a cavity or pocket 1 1 b formed in the body 1 1 of a bearing assembly. The PCD insert 12 itself comprises a tungsten carbide substrate 12a with a polycrystalline diamond (PCD) table 12b formed on the top surface thereof. Note that the brazing material 14 bonds the PCD insert 12 to the bottom surface and sidewall of the cavity 1 1 b, enabling load transfer between the insert and the body 1 1 forming a brazing joint 14a - the braze joint 14a is directly between the pocket 11 b and the PCD insert 12, including the bottom of the pocket.

[0013] Despite the inherent wear resistance of PCD, premature failures of PCD bearings have been observed during downhole drilling operations. These failures occur earlier and more frequently than expected and are characterized by the detachment and liberation of the PCD inserts 13 from the steel housings 1 1 and 11 a as depicted in FIGS. 3 and 4. Examination of failed bearings has revealed that the brazing joints 14a represent the weakest point, with the PCD inserts detaching intact.

[0014] In particular, detailed inspections have shown that brazing defects leading to cracking, voids, delamination, and / or detachment frequently initiate at the interface between the brazing material 14 and the metal substrate (e.g., the body 1 1 or the tungsten carbide substrate 12a of the PCD insert). Thermal stresses are believed to be a primary cause of these cracks. Indeed, joint quality (e.g., strength) of the brazed joint 14a between the PCD insert 12 and the walls / floor of its cavity 1 1 b, which is clearly reduced by such cracks, has been identified as a critical factor of the performance and longevity of PCD bearing assemblies. As a result, the integrity of the brazed joint is of particular concern for overall bearing reliability.

[0015] The persistent occurrence of joint failures and the limitations of brazing as an attachment method highlight the need for a more reliable solution. There remains a need for an improved method of securing PCD bearing elements within their carriers, one that overcomes the weaknesses of brazed joints and provides enhanced mechanical integrity, durability, and inspectability. As such, further development is needed.

[0016] 65DRL-511162-WO-2 2 Attorney Docket: 65DRL-511162-WO-2

[0017] SUMMARY

[0018] Disclosed herein is a method and device for attaching polycrystalline diamond (PCD) bearing elements to bearing carriers in downhole drilling tools. A shape memory ring is used as an intermediate connection component between the PCD bearing element and its receiving pocket within the body of a bearing assembly.

[0019] Initially, the shape memory ring is initially fitted around the PCD bearing element with a controlled gap being therebetween. Then heat is applied and the ring contracts, creating a secure friction fit that retains the PCD element. After the PCD element is retained by the shape memory ring, the combined assembly is positioned within the pocket of the body of the bearing assembly. The assembly is then welded in place to secure the PCD element to the bearing assembly. The method allows for precise control of the retention force between the ring and the PCD bearing element by adjusting the dimensions and shrink parameters of the ring. The welded connection can be inspected for quality assurance. This is suitable for both axial and radial bearing configurations and is compatible with standard post-assembly finishing processes such as EDM cutting, grinding, or polishing.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIGS. 1 A-1 C are diagrams of bearing assemblies including polycrystalline diamond (PCD) inserts.

[0022] FIG. 2 is a cross-sectional view of a PCD insert within a cavity in a body of a bearing assembly.

[0023] FIGS. 3 and 4 are diagrams of bearings including PCD inserts that have failed (detached) during operation.

[0024] FIGS. 5 and 6 are simplified diagrams illustrating how the microstructure of a shape memory material may change.

[0025] FIGS. 7A-7B are diagrams showing the use of a shape memory ring as an intermediate connection component for attaching a PCD insert.

[0026] FIGS. 8A-8C and FIGS. 9A-9D are assembly sequence diagrams depicting the process of expanding, fitting, and contracting the shape memory alloy ring around a PCD insert.

[0027] FIGS. 10A-10B are detailed views of the shape memory ring, showing the gap feature and its relationship to the PCD insert.

[0028] 65DRL-511162-WO-2 3 Attorney Docket: 65DRL-511162-WO-2

[0029] FIGS. 1 1 A-1 1 B are diagrams showing the uniform contraction of the shape memory ring around the PCD insert during the heat-induced phase transformation.

[0030] FIG. 12 is a diagram showing the assembly of the PCD insert and shape memory ring positioned within a pocket of the bearing carrier.

[0031] FIGS. 13A-13C are diagrams showing the welding process used to secure the assembly within the bearing carrier.

[0032] FIGS. 14A-14C are diagrams showing post-assembly finishing processes, such as grinding or EDM cutting, to create a cylindrical bearing surface.

[0033] FIGS. 1 5A-15B are diagrams showing alternative configurations of the shape memory ring, including shorter and longer ring designs for different bearing applications.

[0034] FIGS. 16A-16B are diagrams showing a longer shape memory ring configuration that extends along a greater portion of the height of the PCD insert, providing increased contact area and enhanced retention force.

[0035] FIGS. 17A-17E are diagrams illustrating an embodiment in which the tungsten carbide backing includes an integral collar that provides a mechanical locking interface with the shape memory ring.

[0036] FIGS. 18A-18B are diagrams illustrating an embodiment in which the tungsten carbide backing includes one or more recesses configured to receive mating projections on the inner surface of the shape memory ring.

[0037] FIGS. 19A-19B are diagrams illustrating an alternative projection-recess configuration in which the shape memory ring itself conforms into recesses formed in the tungsten carbide backing during activation.

[0038] DETAILED DESCRIPTION

[0039] The following disclosure enables a person skilled in the art to make and use the subject matter described herein. The general principles outlined in this disclosure can be applied to embodiments and applications other than those detailed above without departing from the spirit and scope of this disclosure. It is not intended to limit this disclosure to the embodiments shown, but to accord it the widest scope consistent with the principles and features disclosed or suggested herein.

[0040] Certain structures, such as components of downhole tools, may be made of materials that are generally durable in terms of high hardness, resistant to erosion, corrosion, and abrasion, and also lightweight due to a relatively low density. Materials exhibiting desirable properties for certain downhole tool applications may also be relatively 65DRL-511162-WO-2 4 Attorney Docket: 65DRL-511162-WO-2 brittle and include materials such as ceramics or hard metal. While the chemical and thermal resistance of brittle materials, such as ceramics, makes them attractive materials for many applications, brittle materials are generally difficult to machine in comparison to metals. This is especially true for polycrystalline diamond (PCD) and tungsten carbide, which are commonly used in bearing assemblies but present unique challenges in terms of machining and reliable attachment. In addition, it may be desirable to connect brittle structures to one or more additional structures to form an assembly. For example, downhole tools generally include a variety of components that are connected together before being positioned within the drill string. Thus, the difficulty to machine brittle materials presents challenges for connecting brittle structures to other structures of an assembly. As explained, it is difficult to successfully form a strong braze joint to certain brittle materials. As a result, alternative connection strategies are required to ensure robust mechanical integration of brittle bearing elements with metallic carriers. To address this issue, metallic connection members, such as sleeves can be machined to size and then press-fit onto the ceramic material by first heating the metallic sleeve for thermal expansion. However, structures designed for a press-fit or interference fit require precision machining and procedures that are prone to error.

[0041] Thus, in accordance with embodiments of this disclosure, connection members may include a shape memory material configured to transition from a first state having a first configuration to a second state having a second configuration, and vice versa, in response to application of a stimulus, such as a temperature, stress (optical stress, magnetic stress, or mechanical stress), or electrical current. The connection members may exhibit super-elastic properties, which may facilitate connections between brittle structures (e.g., ceramic, hard metal, glass, graphite, etc.) without press-fit or gluing procedures. For example, the shape memory material of the connection member may be in a second state below a transition temperature, and an opening within the connection member may be enlarged such that the connection member can be positioned on a brittle structure. Once positioned in a desired location, the connection member may be exposed to a temperature above the transition temperature. Exposing the connection members to a temperature above the transition temperature initiates a state change from the second state back to the first state, and results in a change in volume and configuration (e.g., shape, such as shrinking or expending) to secure the connection member to the brittle structure. This process enables a controlled friction fit between the shape memory material of the connection member and the brittle structure (e.g., a PCD insert), providing

[0042] 65DRL-511162-WO-2 5 Attorney Docket: 65DRL-511162-WO-2 reliable retention without inducing damaging stresses. In other embodiments, instead of exposing the connection member to a temperature above the transition temperature, a stress or an electrical current may be used to initiate the change from the second state back to the first state.

[0043] The following description provides specific details, such as specific shapes, specific sizes, dimensions, specific material compositions, and specific processing conditions, in order to provide a thorough description of embodiments of the present disclosure. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without necessarily employing these specific details. Embodiments of the disclosure may be practiced in conjunction with conventional fabrication techniques employed in the industry. In addition, the description provided below does not form a complete process flow for manufacturing a connection member or a downhole tool. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Additional acts to form a complete connection member or a complete downhole tool from the structures described herein may be performed by conventional fabrication processes and additive manufacturing processes.

[0044] Drawings presented herein are for illustrative purposes only, and are not meant to be actual views of any particular material, component, structure, device, or system. Variations from the shapes depicted in the drawings as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes or regions as illustrated, but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box-shaped may have rough and / or nonlinear features, and a region illustrated or described as round may include some rough and / or linear features. Moreover, sharp angles that are illustrated may be rounded, and vice versa. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a region and do not limit the scope of the present claims. The drawings are not necessarily to scale. Additionally, elements common between figures may retain the same numerical designation.

[0045] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0046] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] 65DRL-511162-WO-2 6 Attorney Docket: 65DRL-511162-WO-2

[0048] As used herein, the term "substantially" in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0 percent met, at least 95.0 percent met, at least 99.0 percent met, at least 99.9 percent met, or even 100.0 percent met.

[0049] As used herein, the term "about," when used in reference to a numerical value for a particular parameter, is inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, "about," in reference to a numerical value, may include additional numerical values within a range of from 90.0 percent to 1 10.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.

[0050] As used herein, the term "shape memory material" includes any suitable shape memory material, including shape memory metal alloys and shape memory polymers. Shape memory metal alloys may include Ni-based alloys, Cu-based alloys, Co-based alloys, Fe-based alloys, Ti-based alloys, Al-based alloys, or any mixture thereof. Shape memory metal alloys may additionally include additional elements, such as Niobium (Nb), which may enhance the shape memory capability of such materials. For example, a shape memory metal alloy may include a 50:50 mixture by weight of nickel and titanium, a 55:45 mixture by weight of nickel and titanium, or a 60:40 mixture by weight of nickel and titanium. Many other compositions are possible and can be selected based on tool requirements and material properties as known in the art. Shape memory polymers may include, for example, epoxy polymers, thermoset polymers, thermoplastic polymers, or combinations or mixtures thereof. Other polymers that exhibit shape memory behavior may also be employed. Shape memory materials are polymorphic and may exhibit two or more crystal structures or states (e.g., phases). Shape memory materials may further exhibit a shape memory effect associated with the state (e.g., phase) transition between two crystal structures or states (e.g., phases), such as austenite and martensite. The austenitic phase exists at elevated temperatures, while the martensitic phase exists at low temperatures.

[0051] 65DRL-511162-WO-2 7 Attorney Docket: 65DRL-511162-WO-2

[0052] The shape memory effect may be triggered by a stimulus that may be thermal, electrical, magnetic, or chemical, and which causes a transition from one solid state to another.

[0053] As used herein, the terms "brittle structure" and "brittle material” refer to materials that have low ductility and, at 20° C., undergo 5% or less elongation (i.e., tensile plastic deformation) before fracturing when tested in accordance with ASTM Test Method under ASTM E399 using a tensile testing machine. The definition of a brittle material as used in this application refers to material that possess a fracture toughness or crack resistance K1 C lower than 20 MPa m1 / 2. As specific non-limiting examples, "brittle structures" and "brittle materials" include ceramics, glasses, graphite, certain metals (hard metals) and alloys, certain polymers, polycrystalline diamonds, etc. Ceramics may be Silicone Nitrides, Silicone Carbides, Aluminum Oxides, Zirconium Oxid or alternative technical ceramics. Hard metals may be Tungsten Carbide, Titanium Carbide, Titanium Nitride, or Tantalum Carbide.

[0054] FIGS. 5-6 are simplified diagrams illustrating how the microstructure of a shape memory material may change. While FIGS. 5-6 specifically illustrate microstructure of shape memory alloys, shape memory polymers may exhibit a similar shape memory effect, as described below. Shape memory materials generally exhibit both a "shape memory effect" and a "pseudoplasticity effect." Described briefly, the shape memory effect refers to the ability of a material to reverse material deformation in response to a temperature- induced state (e.g., phase) transformation. The pseudoelasticity effect refers to the ability of a material to reverse material deformation in response to a stress-induced state (e.g., phase) transformation, such as induced by the application of an external load.

[0055] Referring now to FIG. 5, a shape memory alloy may transform from an original austenitic phase (i.e., a high-temperature phase) to a martensitic phase (i.e., a low- temperature phase) upon cooling. The phase transformation from austenite to martensite may be spontaneous, diffusionless, and temperature dependent. The transition temperatures from austenite to martensite and vice versa vary for different shape memory alloy compositions. For example, the material composition of the shape memory alloy may be selected and / or tailored such that a first transition temperature (e.g., martensite finish temperature (Mf)) of a shape memory alloy occurs within a range of from about -140° C. to about 0° C., and a second transition temperature (e.g., austenite finish temperature (Af)) of the shape memory alloy occurs within a range of from about 0° C. to about 200° C. Different material compositions of shape memory alloys and the transition temperatures are described in Minjuan Wang et al., Martensitic transformation involved mechanical

[0056] 65DRL-511162-WO-2 8 Attorney Docket: 65DRL-511162-WO-2 behaviors and wide hysteresis of NiTiNb shape memory alloys, 22(2) Progress in Natural Science: Materials International 130-138 (2012), available: sciencedirect.com / science / article / pii / S10020071 12000330, the entire contents of which are hereby incorporated herein by this reference.

[0057] The phase transformation from austenite to martensite occurs between a first temperature (Ms), at which austenite begins to transform to martensite and a second, lower temperature (Mf), at which only martensite exists. As shown in FIG. 5 , initially, the crystal structure of martensite is heavily twinned and may be deformed by an applied stress such that the material takes on a new size and / or shape. After the applied stress is removed, the material retains the deformed size and / or shape. However, upon heating, martensite may transform and revert to austenite. The phase transformation occurs between a first temperature (As) at which martensite begins to transform to austenite and a second, higher temperature (Af) at which only austenite exists. Upon a complete transition to austenite, the element returns to its original "remembered" size and / or shape. As used herein, the term "remembered" refers to a configuration to which a material returns spontaneously responsive to a temperature change. Upon a second cooling process and transformation from austenite to martensite, the crystal structure of the martensitic phase is heavily twinned and may be deformed by an applied stress such that the material takes on at least one of a new size and / or shape. The size and / or shape of the material in the previously deformed martensitic phase are not remembered from the initial cooling process. This shape memory effect may be referred to as a one-way shape memory effect, such that the element exhibits the shape memory effect only upon heating as illustrated in FIG. 5.

[0058] Other shape memory alloys possess two-way shape memory, such that a material comprising such a shape memory alloy exhibits this shape memory effect upon heating and cooling. Shape memory alloys possessing two-way shape memory effect may therefore, include two remembered sizes and shapes— a martensitic (i.e., low-temperature) shape and an austenitic (i.e., high-temperature) shape. Such a two-way shape memory effect is achieved by "training." By way of example and not limitation, the remembered austenitic and martensitic shapes may be created by inducing non-homogeneous plastic strain in a martensitic or austenitic phase, by aging under an applied stress, or by thermomechanical cycling. With reference to FIG. 6, when a two-way shape memory alloy is cooled from an austenitic to a martensitic phase, some martensite configurations might be favored, so that the material may tend to adopt a preferred shape. By way of further non-

[0059] 65DRL-511162-WO-2 9 Attorney Docket: 65DRL-511162-WO-2 limiting example, and without being bound by any particular theory, the applied stress may create permanent defects, such that the deformed crystal structure of the martensitic phase is remembered. After the applied stress is removed, the element retains the deformed size and / or shape. Upon heating, martensite may transform and revert to austenite between the first temperature (As) and the second, higher temperature (Af). Upon a complete transition to austenite, the element returns to its original remembered size and shape. The heating and cooling procedures may be repeated such that the material transforms repeatedly between the remembered martensitic and the remembered austenitic shapes.

[0060] In some embodiments, the shape memory alloy material may comprise a nickel- titanium-niobium alloy that includes from about 40% to about 60% nickel by atomic weight, from about 30% to about 40% titanium by atomic weight, and from about 5% to about 20% Niobium by atomic weight. As specific non-limiting examples, the shape memory alloy may include Ni47.5Ti47.5Nb5, Ni45Ti44Nb9, and / or Ni45Ti45Nbi0. In some embodiments, the first temperature (Mf), at which only martensite exists may be about -40° C., and the higher temperature (Af) at which only austenite exists may be about 10° C. By way of non-limiting example, the shape memory alloy or shape memory polymer in a downhole application is to be selected to ensure that for a typical downhole temperature range, such as around 10C. to around 250° C., or 1 ° C. to around 350° C., the shape memory alloy or shape memory polymer is in the austenite phase. The material properties of the shape memory alloy or shape memory polymer are to be selected to allow a desired change in the dimension in the martensitic phase.

[0061] A shape memory polymer may exhibit a similar shape memory effect. Heating and cooling procedures may be used to transition a shape memory polymer between a hard solid state and a soft solid state by heating the polymer above, for example, a melting point or a glass transition temperature (Tg) of the shape memory polymer and cooling the polymer below the melting point or glass transition temperature (Tg) as taught in, for example, U.S. Pat. No. 6,388,043, issued May 14, 2002, and titled "Shape Memory Polymers," the entire disclosure of which is incorporated herein by reference. The shape memory effect may be triggered by a stimulus which may be thermal, electrical, magnetic, or chemical.

[0062] Recall the challenges described hereinabove regarding the brazing of a PCD insert into a pocket within a bearing body. Specifically, the tungsten carbide backing of PCD elements contains only a limited amount of braze-wettable alloys (primarily cobalt), making

[0063] 65DRL-511162-WO-2 10 Attorney Docket: 65DRL-511162-WO-2 reliable brazing difficult to achieve and verify. To provide an alternative mechanical joining method, disclosed herein is a method for attaching PCD bearing elements to both axial and radial bearing carriers used in downhole drilling tools.

[0064] Referring now to FIGS. 7A-7B, ratherthan directly brazing a PCD insert 12to a pocket 11 b within the body 11 of a bearing assembly 10, this method uses a shape memory ring 20 made from a shape memory material, such as those described hereinabove, as an intermediate connection component between the PCD insert 12 and the pocket 11 b. Specifically, as is perhaps best shown in the diagrammatical assembly sequence of FIGS. 8A-8C and FIGS. 9A-9D, the assembly process begins with the PCD insert 12, which comprises a PCD table 12b bonded to a tungsten carbide backing 12a. The shape memory ring 20 is initially provided in its expanded martensitic state, achieved by cooling below the martensite finish temperature (Mf), which may be designed to occur within a range of approximately -140°C to 0°C depending on the selected alloy composition and then expanding the ring by pushing a ball or similar tool through the inner diameter to plastically deform the ring to the desired expanded diameter.

[0065] In this expanded state, the inner diameter of the shape memory ring 20 is larger than the outer diameter of the PCD insert 12, allowing the ring to be easily positioned around the insert without requiring press-fit procedures or specialized tooling. Once the ring is properly positioned on the PCD insert 12, heat is applied to raise the temperature above the austenite finish temperature (Af), which typically ranges from 0°C to 200°C. For example, nickel-titanium-niobium alloys such as Ni475Ti47.5Nb5 or Ni^Ti^Nb^ may exhibit an Mf of approximately -40°C and an Af of approximately 10°C, values selected to ensure the ring remains in its austenitic phase during typical downhole operating temperatures of 1 °C to 350°C, with common operating temperatures being 150°C to 175°C, and occasionally up to 200°C. This temperature-induced phase transformation causes the shape memory ring 20 to transition from martensite to austenite, resulting in the ring shrinking to its remembered configuration and creating a controlled friction fit around the PCD insert 12, forming assembly 25.

[0066] The ring is designed with a specific gap that allows it to be easily fitted around the PCD bearing element during initial assembly. As illustrated in detail in FIGS. 10A-10B, the shape memory ring 20 includes a gap 22 that extends completely through the wall thickness of the ring. This gap 22 serves functions in both the assembly and retention process. For example, the gap 22 is sized to accommodate for manufacturing tolerances of the PCD inserts 12 (which may vary from nominal dimensions) while avoiding excessive expansion of the shape memory ring 22 that could rupture the shape memory ring 22, and during the heat-induced phase transformation to austenite, the shape memory ring 20 contracts uniformly around the circumference of the PCD

[0067] 65DRL-511162-WO-2 11 Attorney Docket: 65DRL-511162-WO-2 insert 12 (as shown in FIGS. 11 A-11 B), creating a controlled interference fit between the shape memory ring 22 and the PCD insert 12 without over-stressing the brittle PCD insert 12.

[0068] The retention force applied to the PCD insert 12 is determined by the interface fit between the shape memory ring 20 the PCD insert 12, and can be specifically designed and adjusted for the application. The retention force can be controlled through optimizing design parameters, such as the wall thickness of the shape memory ring 20, the overall height of the shape memory ring 20, and the gap width 22. Other factors to that may be optimized include balancing the original inner diameter of the shape memory ring 20 relative to the PCD element 12 diameter, the amount of plastic deformation during expansion, and the elastic recovery during heating. Material selection plays a role, as different shape memory materials have different transformation stresses and recoverable strains. The shape memory ring 20 may be trained through thermomechanical cycling to optimize the remembered configuration.

[0069] Note that prior to assembly, both the outer surface of the PCD insert 12 and the inner surface of the shape memory ring 20 are cleaned and prepared, with surface roughness being a parameter affecting the quality of the interface fit. These surfaces are to be free of debris or contaminants to provide for uniform contact, though precision surface preparation required for traditional press-fit assemblies is not necessary due to the conforming nature of the shape memory material during phase transformation.

[0070] As to the sizing of the gap 22, the gap 22 may be configured such that in the austenitic phase, the gap 22 is between approximately 0.001 inch (0.0254 mm) to about 0.1 inch (2.54 mm), or between about 0.005 inch (0.127 mm) to about 0.05 inch (1.27 mm).

[0071] After the application to heat to form the interface fit , the assembly 25 is positioned into pockets 11 b in the bearing carrier 11, as shown in FIG. 12, and subsequently welded in place using methods such as laser or plasma welding, as shown in FIGS. 13A-130. Alternative welding methods may include electron beam welding, tungsten inert gas (TIG) welding, or other suitable joining techniques. The welding process joins two metallic materials (the shape memory ring 20 and the bearing carrier 11 ), and such welding is a well-controlled process that provides stronger attachment compared to brazing. The bearing elements can then undergo final processing like EDM (electrical discharge machining) cutting, grinding, or polishing as needed. For example, for radial bearing applications, the PCD elements 12 typically require finish machining to create a cylindrical bearing surface as shown in FIGS. 14A-14C, which can be accomplished through grinding or EDM cutting to remove the flat facets of the individual PCD inserts 12.

[0072] 65DRL-511162-WO-2 12 Attorney Docket: 65DRL-511162-WO-2

[0073] Note that the shape memory ring 20 does not include any threads on its exterior radius. Likewise, the interior radius of the pocket 11 b formed in the body 1 1 of the bearing assembly 10 is not threaded.

[0074] It is evident that modifications and variations can be made to what has been described and illustrated herein without departing from the scope of this disclosure. For example, in alternative embodiments, the shape memory ring 20 may be configured with different heights to accommodate various design requirements and pocket configurations. As illustrated in FIGS. 15A-15B, a shorter shape memory ring 20’ may be employed that extends only partially along the height of the PCD insert 12. In this configuration, the shorter ring 20' primarily engages the tungsten carbide backing 12a while leaving a greater portion of the PCD table 12b exposed above the ring. This configuration may be advantageous when pocket depth is limited or when maximum exposure of the PCD cutting surface is desired.

[0075] Alternatively, as illustrated in FIGS. 16A-16B, a longer shape memory ring 20" may be utilized that extends along a greater portion of the height of the PCD insert 12. The longer ring 20” provides increased contact area between the shape memory material and the PCD insert 12, potentially offering enhanced retention force and stability. This configuration may partially cover the lower portion of the PCD table 12b in addition to engaging the tungsten carbide backing 12a. As shown in FIG. 16B, when using the longer ring 20”, a correspondingly deeper pocket 11 b' may be machined into the bearing carrier 11 to accommodate the increased ring height. The weld 30 secures the longer ring 20” to the bearing carrier 11 at the pocket interface.

[0076] The selection between shorter and longer ring configurations may be based on factors including the required retention force, available pocket depth in the bearing carrier, desired PCD exposure, operating conditions, and manufacturing constraints. Both configurations maintain the advantages of the shape memory attachment method while offering design flexibility for different bearing applications.

[0077] In other alternative embodiments, the shape memory ring may comprise multiple segments that cooperate to secure the PCD insert, or may include surface features such as ridges, grooves, or textured surfaces to enhance retention.

[0078] A mechanical locking feature may be provided as part of the PDC insert 12. In an exemplary embodiment shown in FIG. 17A-17B, the tungsten carbide backing 12a has a collar 12c, larger than the inner diameter of the shape memory ring. As illustrated in FIGS. 17A-17E, the collar 12c forms an integral portion of the tungsten carbide backing 12a and provides a positive axial engagement surface for the shape memory ring 20. In this embodiment, the shape memory ring 20 is positioned over the PCD insert 12 such that, upon activation and contraction,

[0079] 65DRL-511162-WO-2 13 Attorney Docket: 65DRL-511162-WO-2 the ring 20 or 20' engages both the outer surface of the tungsten carbide backing 12a and an annular shoulder defined by the collar 12c.

[0080] The collar 12c is annular in shape and, as explained, includes a radially extending shoulder or flange configured to seat against a corresponding surface of the shape memory ring 20 once assembled. This geometry provides a defined weld interface that allows for precise placement and uniform weld penetration when the ring is secured to the surrounding bearing carrier or pocket. The collar 12c may also act as a load-bearing feature, distributing thermal and mechanical stresses generated during welding away from the brittle PCD table 12b and into the tougher tungsten carbide backing 12a. As a result, the welded joint maintains dimensional stability and minimizes the risk of cracking or delamination of the PCD insert.

[0081] Note that this configuration differs from the previously described embodiments in that the shape memory ring 20 not only provides a radial clamping force but also establishes an axial mechanical interlock with the collar 12c. As shown in FIG. 17A, the components are initially separate, and the ring 20 is in its expanded martensitic state. FIG. 17B shows the ring 20' after transformation to its austenitic state, having contracted into firm contact with both the tungsten carbide 12a and collar 12c. The collar thereby prevents axial displacement of the PCD insert 12 relative to the ring 20'.

[0082] As further illustrated in FIGS. 17C-17E, this embodiment may include a small radial gap between the shape memory ring 20 and the tungsten carbide 12a prior to activation. When the shape memory ring 20 is heated above its transformation temperature, the gap is closed, resulting in a tight interference fit. The engagement of the collar 12c provides an additional mechanical stop that enhances axial retention, thereby combining the advantages of frictional and mechanical locking.

[0083] Accordingly, the embodiment of FIGS. 17A-17E provides a dual-mode retention mechanism in which the shape memory ring 20 exerts a circumferential compressive force on the PCD insert 12 while the collar 12c provides an axial restraint. This design eliminates the need for adhesives or brazing and further increases resistance to dislodgment under dynamic downhole loading.

[0084] In yet another alternative embodiment, the tungsten carbide backing 12a includes a recess 12d configured to receive a corresponding projection 20a"' formed on an inner surface of a shape memory ring 20 ", as shown in FIGS. 18A-18B. In this configuration, the projection 20a " of the shape memory ring 20"' engages the recess 12d upon contraction of the ring, forming a positive mechanical interlock in addition to the circumferential clamping provided by the shape memory material. The projection-recess interface prevents relative axial and rotational

[0085] 65DRL-511162-WO-2 14 Attorney Docket: 65DRL-511162-WO-2 movement between the PCD insert 12 and the shape memory ring 20", thereby enhancing mechanical stability under high dynamic loading conditions.

[0086] Referring now to FIGS. 19A-19B, additional variations of the projection-recess locking concept are illustrated. In these embodiments, the tungsten carbide backing 12a defines one or more recesses 12d adjacent to the PCD table 12b, and the shape memory ring 20"' contracts into these recesses during activation. Unlike the configuration of FIGS. 18A-18B, the ring 20"' in FIGS. 19A-19B may omit a discrete projection and instead relies on the plastic recovery and conforming behavior of the shape memory material to partially flow into the recess 12d as it transforms to the austenitic phase. This creates a secure mechanical engagement that resists both radial and axial displacement of the ring relative to the insert body.

[0087] The connection member may also be configured with varying wall thicknesses to provide differential clamping forces around the circumference of the PCD insert. Additionally, in some embodiments, a secondary connection member may be employed, such as an outer sleeve or collarthat provides additional mechanical retention or serves as a backup retention mechanism.

[0088] Although this disclosure has been described with a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, can envision other embodiments that do not deviate from the disclosed scope. Furthermore, skilled persons can envision embodiments that represent various combinations of the embodiments disclosed herein made in various ways.

[0089] 65DRL-511162-WO-2 15

Claims

Attorney Docket: 65DRL-511162-WO-2CLAIMS1 . A method of attaching a polycrystalline diamond (PCD) bearing element to a bearing carrier, comprising: providing a PCD insert comprising a PCD table bonded to a tungsten carbide backing; providing a shape memory ring; cooling the shape memory ring below a martensite finish temperature to place the shape memory ring in a martensitic state; expanding an inner diameter of the shape memory ring while in the martensitic state; positioning the expanded shape memory ring around the PCD insert; applying a stimulus to transition the shape memory ring to an at least partial austenitic state, whereby the shape memory ring shrinks to create an interference fit with the PCD insert to form an assembly; and placing the assembly within a pocket formed in the bearing carrier; welding the assembly to the bearing carrier by welding the shape memory ring to the bearing carrier.

2. The method of claim 1, wherein expanding the inner diameter comprises pushing a ball through the inner diameter to plastically deform the shape memory ring.

3. The method of claim 1, wherein the martensite finish temperature is between -140°C and 0°C.

4. The method of claim 1, wherein the austenite finish temperature is between 0°C and 200°C.

5. The method of claim 1, wherein heating the shape memory ring comprises heating to approximately 200°C.

6. The method of claim 1 , wherein the shape memory ring comprises a nickel- titanium-niobium alloy.65DRL-511162-WO-2 16Attorney Docket: 65DRL-511162-WO-27. The method of claim 6, wherein the nickel-titanium-niobium alloy comprises 40-60% nickel, 30-40% titanium, and 5-20% niobium by atomic weight.

8. The method of claim 1, wherein welding comprises one of laser welding, plasma welding, electron beam welding, or tungsten inert gas welding.

9. The method of claim 1, further comprising finish machining the PCD insert after welding to create a bearing surface.

10. The method of claim 9, wherein finish machining comprises one of grinding or electrical discharge machining.11 . The method of claim 1, wherein the gap has a width between 0.001 inch and 0.1 inch in the austenitic state.

12. The method of claim 1 , wherein the tungsten carbide backing includes an integral collar having a radially extending shoulder, and wherein transitioning the shape memory ring to the austenitic state causes the shape memory ring to engage the shoulder of the collar to provide axial restraint of the PCD insert.

13. The method of claim 12, wherein welding the assembly within the bearing carrier is performed such that the weld is formed primarily between the collar and the bearing carrier, thereby distributing welding heat through the tungsten carbide backing and reducing thermal stress on the PCD table.

14. The method of claim 1, wherein the tungsten carbide backing defines at least one recess and the shape memory ring includes a mating projection configured to engage the recess upon contraction of the shape memory ring to provide a mechanical interlock.

15. The method of claim 1, wherein the tungsten carbide backing defines one or more recesses and the shape memory ring, upon transformation to the austenitic state, conforms partially into the recesses to form a mechanical engagement without a discrete projection.65DRL-511162-WO-2 17Attorney Docket: 65DRL-511162-WO-216. A bearing assembly for a downhole tool, comprising: a plurality of assemblies, each comprising: a PCD insert comprising a PCD table bonded to a tungsten carbide backing; an a shape memory ring surrounding at least a portion of the PCD insert and creating an interference fit therewith to form an assembly; a body having a plurality of pockets formed therein, wherein each of the plurality of assemblies is positioned within a corresponding one of the plurality of pockets; and a plurality of welds formed between the body and corresponding ones of the shape memory rings of the plurality of assemblies.

17. The bearing assembly of claim 16, wherein the shape memory ring comprises a nickel-titanium-niobium alloy.

18. The bearing assembly of claim 17, wherein the nickel-titanium-niobium alloy is configured to maintain the austenitic state at downhole operating temperatures between 1 °C and 350°C.

19. The bearing assembly of claim 16, wherein the shape memory ring extends only partially along a height of the PCD insert.

20. The bearing assembly of claim 16, wherein the shape memory ring extends along substantially an entire height of the tungsten carbide backing.

21. The bearing assembly of claim 16 wherein the bearing carrier comprises one of an axial bearing carrier or a radial bearing carrier.

22. The bearing assembly of claim 16, wherein the tungsten carbide backing includes a collar defining an annular shoulder engaged by the shape memory ring to provide axial locking between the shape memory ring and the PCD insert.65DRL-511162-WO-2 18Attorney Docket: 65DRL-511162-WO-223. The bearing assembly of claim 22, wherein the collar provides a weld land such that a weld bead extends circumferentially between the collar and the bearing carrier to secure the assembly and conduct welding heat away from the PCD table.

24. The bearing assembly of claim 16, wherein the tungsten carbide backing defines at least one recess and the shape memory ring includes a corresponding projection that engages the recess to provide a positive mechanical interlock.

25. The bearing assembly of claim 24, wherein the projection-recess interlock restricts both axial and rotational movement of the PCD insert relative tothe shape memory ring.

26. The bearing assembly of claim 1 6, wherein the shape memory ring conforms into a recess defined in the tungsten carbide backing during transformation to the austenitic phase, thereby forming a mechanical locking engagement without a discrete projection.65DRL-511162-WO-2 19

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