A composite metal layer based on CoCrMo alloy and TC4 alloy and a preparation method thereof

Abstract

This invention relates to the field of surface modification of metallic materials, and more particularly to a composite metal layer based on CoCrMo alloy and TC4 alloy and its preparation method. The composite metal layer based on CoCrMo alloy and TC4 alloy comprises a CoCrMo alloy layer, an intermediate alloy layer, and a TC4 alloy layer stacked sequentially; wherein a continuous BCC-type solid solution is formed between the CoCrMo alloy layer and the intermediate alloy layer; a continuous FCC-type solid solution is formed between the intermediate alloy layer and the TC4 alloy layer; the intermediate alloy layer comprises Nb, Ti, Cr, Ni, Cu, and Y2O3. The mixed powder of the intermediate alloy layer can be directionally controlled to react with the phases of the upper and lower layers, forming a BCC phase with CoCrMo and an FCC phase with TC4, without the formation of brittle intermetallic compounds, achieving metallurgical bonding and synergistic performance of the three-layer structure.

Description

Technical Field

[0001] This invention relates to the field of surface modification of metallic materials, and more particularly to a composite metal layer based on CoCrMo alloy and TC4 alloy and its preparation method. Background Technology

[0002] CoCrMo alloys are widely used in medical implants such as artificial joints due to their excellent wear resistance, corrosion resistance, and biocompatibility. TC4 alloys, on the other hand, are indispensable in aerospace and medical device fields due to their lightweight, high strength, and low elastic modulus. In practical applications, it is often necessary to combine the two materials to achieve multiple properties. However, CoCrMo and TC4 have significantly different crystal structures; CoCrMo is an FCC phase, while TC4 is a dual-phase structure of α-HCP and β-BCC. Direct composite formation easily leads to the formation of brittle intermetallic compounds such as TiCo and Cr2Ti at the interface, resulting in low interfacial bonding strength and easy coating peeling failure. Laser cladding technology, as an efficient surface modification method, can achieve metallurgical bonding by controlling the cladding material and process parameters. However, existing cladding powders are mostly designed for single substrates and cannot simultaneously adapt to the phase structure requirements of CoCrMo and TC4.

[0003] Therefore, designing an intermediate layer powder with directional controllable phase structure and relief of interlayer stress, and constructing a three-layer composite coating with synergistic performance, has become the key to solving the composite problem of CoCrMo and TC4. Summary of the Invention

[0004] This invention provides a composite metal layer based on CoCrMo alloy and TC4 alloy and its preparation method, in order to solve the problem of interfacial brittle phase formation in existing CoCrMo and TC4 composite coatings.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The present invention provides a composite metal layer based on CoCrMo alloy and TC4 alloy, comprising a CoCrMo alloy layer, an intermediate alloy layer and a TC4 alloy layer stacked sequentially. A continuous BCC-type solid solution is formed between the CoCrMo alloy layer and the intermediate alloy layer; A continuous FCC-type solid solution is formed between the intermediate alloy layer and the TC4 alloy layer; The intermediate alloy layer comprises the following raw materials in weight percentage: Nb 26%~30%, Ti 18%~24%, Cr 14%~18%, Ni 16%~20%, Cu 6%~10%, Y2O36%~10%.

[0006] In some specific embodiments, the intermediate alloy layer comprises the following raw materials in weight percentage: Nb 28%, Ti 22%, Cr 16%, Ni 18%, Cu 8%, Y2O38%.

[0007] In some specific embodiments, the particle size of the Nb and the Ti is independently 20~50 μm.

[0008] In some specific embodiments, the particle size of Cr and Ni is independently 10~20 μm.

[0009] In some specific embodiments, the Cu particle size is 5~10 μm.

[0010] In some specific embodiments, the particle size of the Y2O3 is 1~5μm.

[0011] In some specific embodiments, the thickness ratio of the CoCrMo alloy layer, the intermediate alloy layer and the TC4 alloy layer is (100~300):(50~150):(200~500).

[0012] A second aspect of the present invention also provides a method for preparing the above-mentioned composite metal layer based on CoCrMo alloy and TC4 alloy, comprising the following steps: Nb, Ti, Cr, Ni, Cu and Y2O3 are mixed and clad onto the surface of TC4 alloy substrate by a first laser cladding process to form an intermediate alloy layer on the surface of TC4 alloy substrate. The CoCrMo alloy is clad onto the surface of the intermediate alloy layer using a second laser cladding process to form a CoCrMo alloy layer on the surface of the intermediate alloy layer.

[0013] In some specific embodiments, the mixing process further includes post-processing. The post-processing includes drying and ball milling the resulting product after mixing.

[0014] In some specific embodiments, the drying is vacuum drying, and the conditions for vacuum drying are: temperature of 100~140℃ and time of 1.5~2.5h.

[0015] In some specific embodiments, the ball milling conditions are as follows: ball-to-material ratio of 4:1 to 6:1, rotation speed of 180 to 220 r / min, time of 3 to 5 h, atmosphere of inert gas, and atmosphere flow rate of 18 to 30 L / min.

[0016] In some specific embodiments, the conditions for the first laser cladding process are: power of 1100~1600W, scanning speed of 10~12mm / s, powder feeding rate of 12~15g / min, and cooling rate >10. 4 K / s, the atmosphere is an inert gas, and the flow rate of the inert atmosphere is 18~30 L / min.

[0017] In some specific embodiments, the conditions for the second laser cladding process are: power of 1500~2100W, scanning speed of 4~8mm / s, powder feeding rate of 18~25g / min, and cooling rate of 10. 2 ~8×10 3 K / s, the atmosphere is an inert gas, and the flow rate of the inert atmosphere is 18~30 L / min.

[0018] In some specific embodiments, before the first laser cladding process, the process further includes: grinding and shaping the TC4 alloy layer substrate.

[0019] In some specific embodiments, after the second laser cladding process is completed, the process further includes: polishing and shaping the clad coating.

[0020] In some specific embodiments, the surface roughness Ra of the CoCrMo alloy layer after polishing is ≤0.8μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The composite metal layer based on CoCrMo alloy and TC4 alloy provided by the present invention includes a CoCrMo alloy layer, an intermediate alloy layer and a TC4 alloy layer arranged sequentially; wherein, a continuous BCC type solid solution transition layer is formed between the CoCrMo alloy layer and the intermediate alloy layer; a continuous FCC type solid solution transition layer is formed between the intermediate alloy layer and the TC4 alloy layer; the intermediate alloy layer includes the following raw materials in mass percentage: Nb 26%~30%, Ti 18%~24%, Cr 14%~18%, Ni 16%~20%, Cu 6%~10%, Y2O3 6~10%. The intermediate alloy layer is composed of five elements—Nb, Ti, Cr, Ni, and Cu—in specific atomic percentages, as well as Y2O3. Its phase reaction with the upper and lower layers can be directionally controlled, and its phase structure can be matched with the upper and lower layers. It reacts with the upper CoCrMo layer to form the BCC phase and with the lower TC4 layer to form the FCC phase. No brittle intermetallic compounds are formed, achieving metallurgical bonding and performance synergy of the three-layer structure. The interfacial bonding strength is >650MPa. This composite metal layer combines the wear and corrosion resistance of CoCrMo with the lightweight and high strength characteristics of TC4, making it suitable for fields such as biomedical implants and aerospace components.

[0022] (2) The method for preparing the composite metal layer based on CoCrMo alloy and TC4 alloy provided by the present invention adopts mature laser cladding technology, the process parameters are easy to control, and it is suitable for industrial production. At the same time, the adjacent layers are connected by a circular arc transition, which effectively alleviates the stress concentration between layers, reduces the probability of crack initiation, and improves the stability of the coating. Attached Figure Description

[0023] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 The image shown is a scanning electron microscope (SEM) image of the intermediate alloy layer powder in Example 1.

[0024] Figure 2 The diagram shown is a simplified cross-sectional microstructure of the composite metal layer in Example 1.

[0025] Figure 3 The image shown is an X-ray diffraction pattern of the junction between the intermediate alloy layer and the TC4 alloy layer in Example 1.

[0026] Figure 4 The image shown is an X-ray diffraction pattern of the junction between the CoCrMo alloy layer and the intermediate alloy layer in Example 1. Detailed Implementation

[0027] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0028] The present invention provides a composite metal layer based on CoCrMo alloy and TC4 alloy, comprising a CoCrMo alloy layer, an intermediate alloy layer and a TC4 alloy layer stacked sequentially. A continuous BCC-type solid solution is formed between the CoCrMo alloy layer and the intermediate alloy layer; A continuous FCC-type solid solution is formed between the intermediate alloy layer and the TC4 alloy layer; The intermediate alloy layer comprises the following raw materials in weight percentage: Nb 26%~30%, Ti 18%~24%, Cr 14%~18%, Ni 16%~20%, Cu 6%~10%, Y2O36%~10%.

[0029] The composite metal layer of this invention constructs a three-layer composite structure consisting of a CoCrMo alloy surface layer, a multi-component mixed powder intermediate alloy layer, and a TC4 alloy bottom layer. The key lies in the formulation design of the multi-component mixed powder and the optimization of the interlayer bonding method. By designing a specific composition for the intermediate alloy layer mixed powder, precise matching with the phase structure of the upper and lower layers is achieved. Specifically: Composed of five elements—Nb, Ti, Cr, Ni, and Cu—and mixed with Y2O3, it reacts with the upper CoCrMo alloy to form the BCC phase and with the lower TC4 to form the FCC phase, achieving a three-layer metallurgical bond and synergistic performance. It exhibits thermodynamic high entropy effect, structural lattice distortion effect, kinetic hysteresis diffusion effect, and performance cocktail effect, resulting in high wear and corrosion resistance and high strength.

[0030] In this invention, the raw materials of the intermediate alloy layer include Nb and Cr as BCC phase-forming elements, Ti as HCP phase-adapting elements, Ni and Cu as FCC phase-inducing elements, and Y2O3 as grain-refining strengthening elements. By controlling the amount of each element within the above range, Nb and Cr synergistically ensure the BCC phase-forming ability, Ni and Cu synergistically ensure the FCC phase-inducing ability, Ti enhances the HCP phase adaptability, and Y2O3 refines the grains.

[0031] In this invention, the selection of elements in the intermediate alloy layer affects the performance of the coating. Elements that easily form brittle phases with Co and Ti, such as Al and V, should be avoided to ensure compatibility with the upper and lower substrates.

[0032] In some embodiments, the intermediate alloy layer comprises the following raw materials in weight percentage: Nb 28%, Ti 22%, Cr 16%, Ni 18%, Cu 8%, Y2O38%.

[0033] In this invention, when the intermediate alloy layer contains 28% Nb, 22% Ti, 16% Cr, 18% Ni, 8% Cu and 8% Y2O3, the intermediate alloy layer and the CoCrMo alloy layer can form a BCC phase during the cladding process, and form a pure FCC phase with the lower TC4 layer, without the formation of brittle phases.

[0034] In some embodiments, the particle size of Nb and Ti is independently 20~50 μm. As an example, the particle size of Nb and Ti can be independently 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm and 50 μm, etc.

[0035] In some embodiments, the particle size of Cr and Ni is independently 10-20 μm. As an example, the particle size of Cr and Ni can be independently 10 μm, 12 μm, 15 μm, 17 μm, 19 μm, and 20 μm, etc.

[0036] In some embodiments, the Cu particle size is 5-10 μm. As an example, the Cu particle size can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, etc.

[0037] In some embodiments, the particle size of the Y2O3 is 1~5 μm. As an example, the particle size of the Y2O3 can be 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm, etc.

[0038] In some embodiments, the thickness ratio of the CoCrMo alloy layer, the intermediate alloy layer, and the TC4 alloy layer is (100~300):(50~150):(200~500). As an example, the thickness ratio of the CoCrMo alloy layer, the intermediate alloy layer, and the TC4 alloy layer can be 100:50:200, 200:100:300, and 300:150:500, etc.

[0039] Preferably, the thickness of the CoCrMo alloy layer is 100~300μm.

[0040] Preferably, the thickness of the intermediate alloy layer is 50~150μm.

[0041] Preferably, the thickness of the TC4 alloy layer is 200~500μm.

[0042] In this invention, the CoCrMo alloy layer provides excellent wear resistance and corrosion resistance.

[0043] In this invention, the intermediate alloy layer achieves phase compatibility and metallurgical bonding between the upper and lower layers. If the intermediate alloy layer is too thin, it is difficult to control the forming quality and the forming quality is poor; if the coating is too thick, the forming stress of the coating is large, which makes the coating prone to cracking and the bonding effect is poor. The intermediate alloy layer is within the above range, which is beneficial to improving the forming quality and performance of the intermediate alloy layer.

[0044] In this invention, the TC4 alloy layer provides lightweight and high-strength matrix support.

[0045] A second aspect of the present invention also provides a method for preparing the above-mentioned composite metal layer based on CoCrMo alloy and TC4 alloy, comprising the following steps: Nb, Ti, Cr, Ni, Cu and Y2O3 are mixed and clad onto the surface of TC4 alloy substrate by a first laser cladding process to form an intermediate alloy layer on the surface of TC4 alloy substrate. The CoCrMo alloy is clad onto the surface of the intermediate alloy layer using a second laser cladding process to form a CoCrMo alloy layer on the surface of the intermediate alloy layer.

[0046] The method for preparing the composite metal layer of the present invention involves laser cladding to deposit the aforementioned alloy powder onto the surface of a substrate. An intermediate alloy layer, composed of five elements (Nb, Ti, Cr, Ni, and Cu) and mixed with Y2O3, reacts with the upper CoCrMo alloy to form a BCC phase and with the lower TC4 to form an FCC phase during the laser cladding process. This achieves metallurgical bonding and synergistic performance of the three-layer structure, exhibiting thermodynamic high entropy effect, structural lattice distortion effect, kinetic hysteresis diffusion effect, and performance cocktail effect, resulting in high wear and corrosion resistance and high strength.

[0047] In some embodiments, the TC4 alloy substrate further includes a pretreatment, which includes polishing, degreasing, derusting and drying the surface of the TC4 alloy substrate.

[0048] In some embodiments, the mixing process further includes post-processing. The post-processing includes drying and ball milling the resulting product after mixing.

[0049] In some embodiments, the drying is vacuum drying, and the conditions for vacuum drying are: temperature of 100~140℃ and time of 1.5~2.5h.

[0050] In some embodiments, the ball milling conditions are as follows: ball-to-material ratio of 4:1 to 6:1, rotation speed of 180 to 220 r / min, time of 3 to 5 h, atmosphere of inert gas, and atmosphere flow rate of 18 to 30 L / min.

[0051] In this invention, the ball milling process is only used to achieve uniform mixing and surface optimization of the raw materials, without changing the original design intention of this particle size range.

[0052] In some embodiments, the conditions for the first laser cladding process are: power of 1100~1600W, scanning speed of 10~12mm / s, powder feeding rate of 12~15g / min, and cooling rate >10. 4The atmosphere is inert gas, with a flow rate of 18-30 L / min. For example, the power can be 1100W, 1200W, 1300W, 1400W, 1500W, and 1600W, etc.; the scanning speed can be 10mm / s, 10.5mm / s, 11mm / s, 11.5mm / s, and 12mm / s, etc.; the powder feeding rate can be 12g / min, 13g / min, 14g / min, and 15g / min, etc.; the inert gas flow rate can be 18L / min, 20L / min, 25L / min, and 30L / min, etc.; the inert gas includes, but is not limited to, nitrogen and argon, etc.; considering the upper limit of process adaptability, the upper limit of the cooling rate is ≤10. 6 K / s.

[0053] In some embodiments, the conditions for the second laser cladding process are: power of 1500~2100W, scanning speed of 4~8mm / s, powder feeding rate of 18~25g / min, and cooling rate of 10. 2 ~8×10 3 The atmosphere is inert gas, with a flow rate of 18-30 L / min. For example, the power can be 1500W, 1800W, 1900W, 2000W, and 2100W, the scanning speed can be 4mm / s, 4.5mm / s, 5mm / s, 5.5mm / s, 6mm / s, 7mm / s, and 8mm / s, the powder feed rate can be 18g / min, 20g / min, 21g / min, 22g / min, 23g / min, 24g / min, and 25g / min, and the cooling rate can be 10... 2 K / s, 10 3 K / s and 8×10 3 The flow rate of the inert atmosphere can be 18 L / min, 20 L / min, 25 L / min, and 30 L / min, etc.; the inert gas includes, but is not limited to, nitrogen and argon.

[0054] This invention, by simultaneously controlling the laser power, laser scanning rate, and powder feeding rate within a certain range, helps to further improve the quality of refractory high-entropy alloy coatings, thereby enhancing the coating's resistance to high-temperature oxidation and wear resistance.

[0055] In this invention, inert gas protection is applied during the laser cladding process, and the entire cladding process is protected with inert gas through a protective atmosphere chamber.

[0056] In some embodiments, prior to the first laser cladding process, the process further includes: grinding and shaping the TC4 alloy layer substrate.

[0057] In some embodiments, after the second laser cladding process is completed, the process further includes: grinding and shaping the clad coating. By grinding and shaping the TC4 alloy substrate and the coating after the second laser cladding process, a smooth transition between layers can be ensured. The grinding and shaping can be achieved by CNC grinding equipment, and the process can also remove oxide scale and burrs.

[0058] In some embodiments, the surface roughness Ra of the CoCrMo alloy layer after polishing is ≤0.8μm.

[0059] In some embodiments, the arc transition is processed using CNC grinding equipment.

[0060] In this invention, adjacent layers are connected by a circular arc with a radius of 1 mm, which can effectively disperse interlayer stress and avoid crack initiation caused by stress concentration.

[0061] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Example 1 A composite metal layer based on CoCrMo alloy and TC4 alloy includes a CoCrMo alloy layer with a thickness of 200 μm, an intermediate alloy layer with a thickness of 100 μm and a TC4 alloy layer with a thickness of 300 μm stacked sequentially; a continuous BCC-type solid solution is formed between the CoCrMo alloy layer and the intermediate alloy layer; a continuous FCC-type solid solution is formed between the intermediate alloy layer and the TC4 alloy layer. The intermediate alloy layer is composed of the following raw materials in weight percentage: 28%Nb, 22%Ti, 16%Cr, 18%Ni, 8%Cu, 8%Y2O3; The method for preparing the composite metal layer based on CoCrMo alloy and TC4 alloy includes the following steps: (1) Preparation of intermediate alloy layer powder: Nb, Ti, Cr, Ni, Cu and Y2O3 were mixed and placed in a vacuum drying oven and dried in a vacuum oven at 120℃ for 2h. After drying, the mixture was placed in a ball mill protected by argon gas (flow rate of 20L / min) and ball milled for 4h at a ball-to-material ratio of 5:1 and a rotation speed of 200r / min to obtain a uniformly mixed intermediate alloy powder. (2) Substrate pretreatment: The surface of the TC4 alloy sheet is successively polished and shaped, ultrasonically degreased with acetone and ethanol, derusted with sandpaper and dried to obtain the treated TC4 alloy sheet. (3) Intermediate alloy layer cladding: Intermediate alloy powder was clad onto the surface of TC4 substrate using a fiber laser cladding machine. The process parameters were: laser power 1300W, scanning speed 11mm / s, powder feeding rate 13g / min, atmosphere argon, argon flow rate 25L / min, and cooling rate 1.5×10 4 K / s, causing the intermediate alloy layer to react with the TC4 alloy layer to generate the FCC phase, thereby forming an intermediate alloy layer on the surface of the TC4 alloy substrate; (4) Surface cladding: CoCrMo alloy powder was clad onto the surface of the intermediate alloy layer using a fiber laser cladding machine. The process parameters were as follows: laser power 1900W, scanning speed 5mm / s, powder feeding rate 22g / min, atmosphere argon, argon flow rate 20L / min, and cooling rate 5×10 2 K / s ensures that the intermediate alloy layer reacts with the CoCrMo surface layer to form the BCC phase, thereby forming a CoCrMo alloy layer on the surface of the intermediate alloy layer. (5) Post-processing: The coating is reshaped using CNC grinding equipment, and the interlayer arc transition structure is processed with an arc radius of 1mm. After grinding, the surface roughness of the CoCrMo alloy layer Ra≤0.8μm is removed to remove oxide scale and burrs.

[0063] Figure 1 The image shown is a scanning electron microscope (SEM) image of the intermediate alloy layer powder in Example 1. Figure 1 It is evident that the mixed powder of the intermediate alloy layer has a regular particle shape, appearing as spherical or irregular blocks, without obvious adhesion or agglomeration. The particles of different components are uniformly dispersed, with no local elemental segregation, and the particle size distribution is uniform. This uniform particle size distribution and dispersion provides a structural basis for the rapid diffusion and full reaction of each element during laser cladding, avoiding phase structure inhomogeneity problems caused by particle agglomeration or particle size imbalance.

[0064] Figure 2 The diagram shown is a simplified cross-sectional microstructure of the composite metal layer in Example 1. Figure 2 It is evident that the composite metal layer exhibits a clear three-layer structure from bottom to top, with continuous interlayer interfaces and no obvious defects such as porosity or cracks: the bottom layer is a TC4 alloy substrate, maintaining its inherent HCP+BCC dual-phase structure; the middle alloy layer is a mixed structure of FCC and BCC phases, serving as a transition layer to achieve phase compatibility between the upper and lower layers; the surface layer is a CoCrMo alloy layer, exhibiting a single FCC phase structure. Crucially, the middle alloy layer forms a continuous FCC-type solid solution at the interface with the TC4 bottom layer and a continuous BCC-type solid solution at the interface with the CoCrMo surface layer, without the presence of brittle intermetallic compounds such as TiCo and Cr2Ti. The smooth interlayer transitions directly demonstrate the design goal of metallurgical bonding and performance synergy.

[0065] Figure 3The image shown is an X-ray diffraction pattern of the junction between the intermediate alloy layer and the TC4 alloy layer in Example 1. Figure 3 It is evident that characteristic diffraction peaks of the HCP, FCC, and BCC phases appeared at the junction. These peaks exhibited high intensity and sharp shape, without any impurity peaks from brittle intermetallic compounds. This indicates that the intermediate alloy layer, through the synergistic effect of Nb, Ti, Cr, Ni, and Cu, successfully achieved phase structure compatibility with the upper and lower substrate layers, without generating any ineffective impurity phases. This aligns with the core invention principle of "directionally controlled phase reaction," providing a phase structure guarantee for high-strength interlayer bonding.

[0066] Figure 4 The image shown is an X-ray diffraction pattern of the junction between the CoCrMo alloy layer and the intermediate alloy layer in Example 1. Figure 4 It was observed that characteristic diffraction peaks of the FCC and BCC phases appeared at the junction, without interference from other impurity phase peaks. This indicates that the phase structure of the CoCrMo alloy layer did not undergo distortion during the laser cladding process, and no brittle phase was formed after reacting with the intermediate alloy layer. This result confirms the rationality of the second laser cladding process parameters, ensuring the excellent wear and corrosion resistance of the surface layer.

[0067] Example 2 The difference from Example 1 is that the surface cladding process parameters are adjusted as follows: laser power is 1500W, scanning speed is 8mm / s, powder feeding rate is 18g / min, argon flow rate is 20L / min, and cooling rate is 1.2×10⁻⁶. 3 K / s, and everything else is the same as in Example 1.

[0068] Example 3 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 26% Nb, 23% Ti, 17% Cr, 18% Ni, 8% Cu, and 8% Y2O3, while the others are the same as in Example 1.

[0069] Example 4 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 26% Nb, 18% Ti, 17% Cr, 20% Ni, 10% Cu, and 9% Y2O3, while the others are the same as in Example 1.

[0070] Example 5 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 26% Nb, 20% Ti, 18% Cr, 19% Ni, 9% Cu, and 8% Y2O3, while the others are the same as in Example 1.

[0071] Example 6 The difference from Example 1 is that the laser power is 1100W during the intermediate alloy layer cladding, while all other aspects are the same as in Example 1.

[0072] Example 7 The difference from Example 1 is that the laser power is 1200W in the intermediate alloy layer cladding, while all other aspects are the same as in Example 1.

[0073] Example 8 The difference from Example 1 is that the laser power is 1400W in the intermediate alloy layer cladding, while all other aspects are the same as in Example 1.

[0074] Example 9 The difference from Example 1 is that the laser power is 1500W in the intermediate alloy layer cladding, while everything else is the same as in Example 1.

[0075] Example 10 The difference from Example 1 is that the laser power is 1600W in the intermediate alloy layer cladding, while all other aspects are the same as in Example 1.

[0076] Comparative Example 1 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 26% Nb, 22% Ti, 16% Cr, 21% Ni, 7% Cu, and 8% Y2O3, while the others are the same as in Example 1.

[0077] Comparative Example 2 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 28% Nb, 21% Ti, 16% Cr, 18% Ni, 11% Cu, and 6% Y2O3, while the others are the same as in Example 1.

[0078] Comparative Example 3 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 28% Nb, 22% Ti, 16% Cr, 17% Ni, 6% Cu, and 11% Y2O3, while the others are the same as in Example 1.

[0079] Comparative Example 4 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 30% Nb, 24% Ti, 18% Cr, 19% Ni, 9% Cu, and 0% Y2O3, while the others are the same as in Example 1.

[0080] Comparative Example 5 The difference from Example 1 is that the intermediate alloy layer is composed of the following raw materials in terms of mass percentage: 28% Nb, 23% Ti, 16% Cr, 19% Ni, 9% Cu, and 5% Y2O3, while the others are the same as in Example 1.

[0081] Comparative Example 6 The difference from Example 1 is that the laser power in the surface cladding is 2300W, while all other aspects are the same as in Example 1.

[0082] Comparative Example 7 The difference from Example 1 is that the laser power is 2000W in the intermediate alloy layer cladding, while everything else is the same as in Example 1.

[0083] Comparative Example 8 The difference from Example 1 is that the laser power is 2100W in the intermediate alloy layer cladding, while everything else is the same as in Example 1.

[0084] Comparative Example 9 The difference from Example 1 is that the thickness of the CoCrMo alloy layer is 200 μm, the thickness of the intermediate alloy layer is 200 μm, and the thickness of the TC4 alloy layer is 200 μm. All other aspects are the same as in Example 1.

[0085] Comparative Example 10 The difference from Example 1 is that the CoCrMo alloy layer is 300 μm thick, the intermediate alloy layer is 200 μm thick, and the TC4 alloy layer is 400 μm thick. All other aspects are the same as in Example 1.

[0086] Comparative Example 11 The difference from Example 1 is that the scanning speed in the surface cladding is 40 m / s, while the rest is the same as in Example 1.

[0087] Comparative Example 12 The difference from Example 1 is that the scanning speed during the intermediate alloy layer cladding is 50 m / s, while the rest is the same as in Example 1.

[0088] Comparative Example 13 The difference from Example 1 is that the TC4 alloy sheet was not pretreated, but otherwise it is the same as Example 1.

[0089] Comparative Example 14 The difference from Example 1 is that neither the intermediate alloy layer cladding nor the surface cladding is gas protected; otherwise, they are the same as in Example 1.

[0090] Performance testing The composite metal layers in the examples and comparative examples were subjected to the following performance tests: Test method for coating forming quality: Determined according to national standard GB / T 36591-2018; Test method for interfacial bonding strength: determined according to national standard GB / T 44990-2024; Test method for surface wear rate: determined according to national standard GB / T 1768-2020; The test method for the tensile strength of the bottom layer was as follows: The test was conducted in accordance with the national standard GB / T 228.1-2021. The test results are shown in Table 1.

[0091] Table 1 Performance test results of the composite metal layers in the examples and comparative examples

[0092] Comparing Comparative Examples 1-5 with Example 1 in Table 1, it can be seen that the Ni content in Comparative Example 1 is not within the range of 26-30%, the Cu content in Comparative Example 2 is not within the range of 6-10%, the Y₂O₃ content in Comparative Example 3 is not within the range of 6-10%, no Y₂O₃ was added in Comparative Example 4, and the Y₂O₃ content in Comparative Example 5 is not within the range of 6-10%. The coating forming quality of these comparative examples is poor or average, and the interfacial bonding strength, surface wear rate, and tensile strength of the underlying layer are all significantly worse than those of Example 1. Therefore, it can be concluded that the elements in the intermediate alloy layer powder need to work synergistically within a specific atomic percentage range. The absence of key elements or exceeding the ratio range will disrupt the phase structure compatibility, leading to a decrease in performance.

[0093] According to the comparison of Comparative Examples 6-8 with Example 1 in Table 1, the surface cladding power of Comparative Example 6 is greater than 2100W, and the performance of the coating is not as good as that of Example 1. Too high laser power can easily lead to high input energy, element burn-out, and the formation of defects. The intermediate alloy layer cladding power of Comparative Examples 7 and 8 is greater than 1900W, and the performance of the coating is not as good as that of Example 1. Too high laser power can easily lead to high input energy, element burn-out, and the formation of defects. The coating forming quality is poor. It can be concluded that the laser power of ultra-high speed laser cladding has a significant impact on the performance of the coating.

[0094] Comparing Comparative Examples 9-10 with Example 1 in Table 1, it can be seen that the coating thickness of Comparative Example 9 is less than that of Example 1, while the coating thickness of Comparative Example 10 is greater than that of Example 1. The coating forming quality of both is poor, with interface bonding strength, surface wear rate, and underlayer tensile strength significantly lower than those of Example 1. This indicates that excessively thin coatings lead to insufficient bonding, while excessively thick coatings cause stress concentration, both of which impair interlayer synergy.

[0095] According to the comparison between Comparative Examples 11-12 and Example 1 in Table 1, the surface cladding scanning speed of Comparative Example 11 and the intermediate alloy layer cladding scanning speed of Comparative Example 12 are much higher than those of Example 1. The coating forming quality is poor, with an increase in unmelted particles, and the interfacial bonding strength, surface wear rate, and tensile strength of the underlying layer are significantly inferior to those of Example 1. Therefore, the surface cladding scanning speed needs to be controlled within a reasonable range; excessive speed will lead to abnormal cooling rates, preventing the formation of a stable phase structure and affecting the bonding quality.

[0096] Comparing Comparative Examples 13-14 with Example 1 in Table 1, it can be seen that Comparative Example 13 did not undergo surface treatment, and residual impurities led to a decrease in interfacial bonding strength; Comparative Example 14 had no gas protection during the cladding process, resulting in severe oxidation, both significantly inferior to Example 1. This indicates that substrate surface pretreatment and gas protection during the cladding process are necessary conditions to ensure coating performance and can effectively avoid problems such as oxidation and residual impurities.

[0097] Comparing Examples 6 and 10 with Example 1 in Table 1, it can be seen that Example 6 has slight porosity due to low power, while Example 10 has localized microcracks due to high power, resulting in a slight decrease in performance. This indicates that the suitable range for the cladding power of the intermediate alloy layer is 1200~1500W, within which the powder can be fully melted and the heat-affected zone can be avoided from being too large.

[0098] According to Examples 1-5 and 7-9 in the table, the three-layer composite coating of the present invention, under the optimized ratio of intermediate alloy layer, cladding parameters and preparation process, has excellent or good coating quality, and exhibits excellent interlayer bonding performance, wear resistance and mechanical strength. It solves the interfacial brittleness problem of direct composite of CoCrMo and TC4, and realizes the synergistic performance of the two materials.

[0099] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A composite metal layer based on CoCrMo alloy and TC4 alloy, characterized in that, It includes a CoCrMo alloy layer, an intermediate alloy layer and a TC4 alloy layer stacked in sequence; A continuous BCC-type solid solution is formed between the CoCrMo alloy layer and the intermediate alloy layer; A continuous FCC-type solid solution is formed between the intermediate alloy layer and the TC4 alloy layer; The intermediate alloy layer comprises the following raw materials in weight percentage: Nb 26%~30%, Ti 18%~24%, Cr 14%~18%, Ni 16%~20%, Cu 6%~10%, Y2O3 6%~10%.

2. The composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 1, characterized in that, The intermediate alloy layer comprises the following raw materials in weight percentage: Nb 28%, Ti 22%, Cr 16%, Ni 18%, Cu 8%, Y2O3 8%.

3. The composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 1, characterized in that, The particle size of Nb and Ti is independently 20~50 μm; The particle size of Cr and Ni is independently 10~20 μm; The Cu has a particle size of 5~10μm; The particle size of the Y2O3 is 1~5μm.

4. The composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 1, characterized in that, The thickness ratio of the CoCrMo alloy layer, the intermediate alloy layer and the TC4 alloy layer is (100~300):(50~150):(200~500).

5. A method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to any one of claims 1 to 4, characterized in that, Includes the following steps: Nb, Ti, Cr, Ni, Cu and Y2O3 are mixed and clad onto the TC4 alloy substrate using a first laser cladding process to form an intermediate alloy layer on the surface of the TC4 alloy substrate. The CoCrMo alloy is clad onto the surface of the intermediate alloy layer using a second laser cladding process to form a CoCrMo alloy layer on the surface of the intermediate alloy layer.

6. The method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 5, characterized in that, The mixing process also includes post-processing. The post-processing includes: drying and ball milling the resulting product after mixing; The drying process is vacuum drying, and the vacuum drying conditions are: temperature 100~140℃, time 1.5~2.5h; The ball milling conditions are as follows: ball-to-material ratio of 4:1 to 6:1, rotation speed of 180 to 220 r / min, time of 3 to 5 h, atmosphere of inert gas, and atmosphere flow rate of 18 to 30 L / min.

7. The method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 5, characterized in that, The conditions for the first laser cladding process are: power of 1100~1600W, scanning speed of 10~12mm / s, powder feeding rate of 12~15g / min, and cooling rate >10. 4 K / s, the atmosphere is an inert gas, and the flow rate of the inert gas is 18~30L / min.

8. The method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 5, characterized in that, The conditions for the second laser cladding process are: power of 1500~2100W, scanning speed of 4~8mm / s, powder feeding rate of 18~25g / min, and cooling rate of 10. 2 ~8×10 3 K / s, the atmosphere is an inert gas, and the flow rate of the inert gas is 18~30L / min.

9. The method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 5, characterized in that, Before the first laser cladding process, the process also includes: grinding and shaping the TC4 alloy layer substrate. After the second laser cladding process is completed, the process also includes polishing and shaping the clad coating.

10. The method for preparing a composite metal layer based on CoCrMo alloy and TC4 alloy according to claim 9, characterized in that, The surface roughness Ra of the CoCrMo alloy layer after polishing is ≤0.8μm.

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