TC4 titanium alloy surface composite wear-resistant coating and preparation method therefor

Abstract

Disclosed in the present invention are a TC4 titanium alloy surface composite wear-resistant coating and a preparation method therefor. The wear-resistant coating comprises a transition layer and a surface layer; the transition layer is attached to the surface of a TC4 titanium alloy by means of laser cladding, and the surface layer is attached to the transition layer by means of laser cladding; the transition layer comprises 70-90% of TC4 particles and 10-30% of WC particles; and the surface layer comprises 50-70% of TC4 particles and 30-50% of WC particles. The TC4 titanium alloy surface composite wear-resistant coating is provided with the transition layer and the surface layer, and the transition layer contains fewer WC particles than the surface layer; the transition layer contains more TC4 particles, and as the base material is also TC4 titanium alloy, the cladding performance and effect of laser cladding are better, and the bonding toughness is better, enhancing the bonding force between the transition layer and the surface of the TC4 titanium alloy. Moreover, the surface layer contains more WC particles, enhancing the wear resistance of the surface layer; and as the transition layer and the surface layer use the same cladding material, the bonding force and toughness of the transition layer and the surface layer are better.

Description

A composite wear-resistant coating on the surface of TC4 titanium alloy and its preparation method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 202310690832.X filed with the Patent Office of China on June 12, 2023, entitled "A composite wear-resistant coating on the surface of TC4 titanium alloy and its preparation method", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of TC4 titanium alloy surface treatment, in particular to a TC4 titanium alloy surface composite wear-resistant coating and a preparation method thereof. Background Art

[0004] TC4 titanium alloy, also known as Ti-6Al-4V, is a (α+β) phase duplex titanium alloy widely used in aerospace, shipbuilding, petrochemical, military, medical and biological fields. TC4 titanium alloy has advantages such as high specific strength and good biocompatibility. However, TC4 titanium alloy also has disadvantages such as low hardness, poor wear resistance, high friction coefficient, easy oxidation at high temperatures, and high resistance to processing deformation, which limit the application of TC4 titanium alloy. Therefore, in order to expand the application range of TC4 titanium alloy, in the existing technology, the surface of TC4 titanium alloy is usually modified to enhance the performance of TC4 titanium alloy.

[0005] Currently, laser cladding is primarily performed on the surface of TC4 titanium alloy. The materials used for laser cladding primarily include metal powder, ceramic powder, and metal-ceramic composite powder. Ceramic materials generally offer strong wear resistance, high hardness, and good chemical stability, but their brittleness limits many of their applications. Metal materials, on the other hand, have poor hardness and wear resistance, but possess a certain degree of plasticity and toughness. Metal-ceramic composite powders offer superior overall performance, combining the strong wear resistance of ceramics with the good toughness of metals. However, existing laser cladding coatings have poor compatibility with the TC4 titanium alloy substrate, making them prone to cracking or flaking.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide a composite wear-resistant coating on the surface of TC4 titanium alloy and a preparation method thereof, so as to solve the problem that the above-mentioned laser cladding coating has poor compatibility with the TC4 titanium alloy substrate and the coating is easy to crack or peel off.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a composite wear-resistant coating on the surface of TC4 titanium alloy, comprising a transition layer and a surface layer; the transition layer is attached to the surface of the TC4 titanium alloy by laser cladding, and the surface layer is attached to the transition layer by laser cladding;

[0010] The raw materials of the transition layer include the following components by weight percentage: 70-90% TC4 particles and 10-30% WC particles; the raw materials of the surface layer include the following components by weight percentage: 50-70% TC4 particles and 30-50% WC particles.

[0011] The TC4 titanium alloy surface composite wear-resistant coating also includes one or more reinforcement layers, which are located between the transition layer and the surface layer. The raw materials of the reinforcement layer include the following components in weight percentage: 60-70% TC4 particles and 30-40% WC particles. The weight percentage of TC4 particles in the reinforcement layer is less than the weight percentage of TC4 particles in the transition layer, and the weight percentage of TC4 particles in the reinforcement layer is greater than the weight percentage of TC4 particles in the transition layer.

[0012] In the composite wear-resistant coating on the surface of the TC4 titanium alloy, the powder particle size of the WC particles is 50 to 150 μm, and the powder particle size of the TC4 particles is 50 to 120 μm.

[0013] In the composite wear-resistant coating on the surface of the TC4 titanium alloy, the total thickness of the transition layer and the surface layer is 4 to 7 mm.

[0014] The present invention also provides a method for preparing a composite wear-resistant coating on the surface of a TC4 titanium alloy, which is used to prepare the composite wear-resistant coating on the surface of the TC4 titanium alloy, comprising the following steps:

[0015] Pretreatment: Clean the surface of TC4 titanium alloy, dry it and bake it to obtain TC4 titanium alloy substrate;

[0016] Weighing TC4 particles and WC particles: drying the TC4 particles and WC particles, weighing the TC4 particles and WC particles according to the ratio of the transition layer, and mixing them to obtain a transition layer powder; then weighing the TC4 particles and WC particles according to the ratio of the surface layer, and mixing them to obtain a surface layer powder;

[0017] First laser cladding: a protective gas is introduced to transport transition layer powder to the TC4 titanium alloy substrate, and the TC4 titanium alloy substrate is subjected to the first laser cladding to form a transition layer on the surface of the TC4 titanium alloy substrate to obtain a transition TC4 titanium alloy substrate;

[0018] Second laser cladding: A protective gas is introduced to transport the surface layer powder to the transition TC4 titanium alloy substrate, and the transition TC4 titanium alloy substrate is laser clad for the second time to form a surface layer on the surface of the transition layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0019] In the method for preparing the composite wear-resistant coating on the surface of the TC4 titanium alloy, in the first laser cladding and the second laser cladding steps, the laser power is 2100-2300 W, the output continuous wavelength is 750-1070 nm, and the spot diameter is 1.2 mm-7 mm.

[0020] In the preparation method of the TC4 titanium alloy surface composite wear-resistant coating, in the first laser cladding and the second laser cladding steps, the gas flow rate for conveying transition layer powder or surface layer powder is set to 4-6 L / min, the protective gas is set to 9-10 L / min, the powder feeding rate of the transition layer powder is 3.6-3.8 r / min, and the powder feeding rate of the surface layer powder is 4.0-4.2 r / min. The protective gas and the powder feeding gas of the laser powder feeder are argon and helium with a purity of 99.999%.

[0021] In the method for preparing the composite wear-resistant coating on the surface of the TC4 titanium alloy, in the pretreatment step, the step of cleaning the surface of the TC4 titanium alloy includes: polishing the surface of the TC4 titanium alloy and degreasing it with acetone; and then preheating it at 300°C for 28 to 35 minutes.

[0022] A technical solution in the present invention can have the following beneficial effects:

[0023] The composite wear-resistant coating on the surface of the TC4 titanium alloy comprises a transition layer and a surface layer, wherein the WC particle content of the transition layer is less than that of the surface layer. The transition layer contains more TC4 particles, and since the base material is also TC4 titanium alloy, the cladding performance and effect are improved during laser cladding, and the bonding toughness is improved, which can enhance the bonding strength between the transition layer and the TC4 titanium alloy surface. The surface layer contains more WC particles, which can enhance the wear resistance of the surface layer. Since the transition layer and the surface layer use the same cladding material, only the specific content is different, the bonding strength and toughness of the transition layer and the surface layer are better during laser cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a micrograph of the interface bonding between the composite wear-resistant coating on the surface of the TC4 titanium alloy and the TC4 titanium alloy substrate of Example 1 of the present invention;

[0025] FIG2 is a micrograph of the interface bonding between the composite wear-resistant coating on the surface of the TC4 titanium alloy and the TC4 titanium alloy substrate of Example 2 of the present invention;

[0026] 3 is a metallographic microstructure diagram of the lower portion of the composite wear-resistant coating on the surface of the TC4 titanium alloy of Example 2 of the present invention;

[0027] 4 is a metallographic microstructure diagram of the upper portion of the composite wear-resistant coating on the surface of TC4 titanium alloy in Example 2 of the present invention;

[0028] FIG5 is a partial enlarged view of the composite wear-resistant coating on the surface of the TC4 titanium alloy of Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further illustrated below by way of specific embodiments. To facilitate understanding of the present invention, the present invention will be described in more detail below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0030] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] 1 to 5 , the present invention provides a composite wear-resistant coating on the surface of a TC4 titanium alloy, comprising a transition layer and a surface layer; the transition layer is attached to the surface of the TC4 titanium alloy by laser cladding, and the surface layer is attached to the transition layer by laser cladding;

[0033] The raw materials of the transition layer include the following components by weight percentage: 70-90% TC4 particles and 10-30% WC particles; the raw materials of the surface layer include the following components by weight percentage: 50-70% TC4 particles and 30-50% WC particles.

[0034] In the existing methods for improving the wear resistance and hardness of TC4 titanium alloy surfaces, due to the insufficient bonding strength and toughness between the cladding material and the TC4 titanium alloy surface, usually only a single layer or a small number of layers of coating can be clad on the TC4 titanium alloy surface; if the thickness of the cladding coating is increased, or laser cladding repair is performed, the coating is prone to various defects such as cracks and holes.

[0035] The composite wear-resistant coating on the surface of the TC4 titanium alloy uses TC4 particles and WC particles as cladding materials. WC particles, that is, tungsten carbide particles, are a compound composed of tungsten and carbon, with the advantages of high melting point, high hardness, stable chemical properties and good fracture toughness. Compared with existing Ti+TiC coatings, TC4+NiCr-Cr3C2, Ti / AlB4C / C and other coatings, the linear expansion coefficient between WC particles and TC4 is closer, which improves the compatibility of the coating with the TC4 titanium alloy matrix and reduces the situation where the coating is prone to cracking or peeling. Moreover, WC reacts chemically with TC4 under high temperature conditions. During the laser cladding process, some WC particles react with TC4 to obtain TiC hard reinforcement phase α-Ti and matrix phase β-Ti, thereby enhancing the wear resistance of the coating.

[0036] TC4 particles are TC4 titanium alloy particles. The transition layer and the surface layer introduce the base material, which makes the cladding performance and effect better. Moreover, it also improves the bonding strength and toughness between the cladding material and the surface of the TC4 titanium alloy, and reduces the various defects such as cracks and holes in the composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0037] The composite wear-resistant coating on the surface of the TC4 titanium alloy comprises a transition layer and a surface layer, wherein the WC particle content of the transition layer is less than that of the surface layer. The transition layer contains more TC4 particles, and since the base material is also TC4 titanium alloy, the cladding performance and effect are improved during laser cladding, and the bonding toughness is improved, which can enhance the bonding between the transition layer and the TC4 titanium alloy surface. The surface layer contains more WC particles, which can enhance the wear resistance of the surface layer. Since the transition layer and the surface layer use the same cladding material, only the specific content is different, the bonding strength and toughness of the transition layer and the surface layer are better during laser cladding.

[0038] Specifically, it also includes one or more reinforcement layers, which are located between the transition layer and the surface layer. The raw materials of the reinforcement layer include the following components in weight percentage: 60-70% TC4 particles and 30-40% WC particles. The weight percentage of TC4 particles in the reinforcement layer is less than the weight percentage of TC4 particles in the transition layer, and the weight percentage of TC4 particles in the reinforcement layer is greater than the weight percentage of TC4 particles in the transition layer.

[0039] In some embodiments of the present invention, multiple reinforcement layers are provided between the transition layer and the surface layer. In one specific embodiment, three reinforcement layers are provided. The reinforcement layers are provided between the transition layer and the surface layer. When the surface layer is worn, the reinforcement layers are exposed. The transition layer is exposed only after the reinforcement layers are completely worn. This structure further improves the wear resistance of the composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0040] The reinforcement layer also uses TC4 particles and WC particles as cladding materials. The proportion of WC particles in the reinforcement layer is smaller than that in the surface layer and higher than that in the transition layer, so that the content of WC particles gradually increases from the transition layer to the surface layer, while the content of TC4 particles gradually decreases from the transition layer to the surface layer.

[0041] The TC4 particle content of the three reinforcement layers decreases from the inside out, while the WC particle content increases, with the WC particle content gradually transitioning from the inside out. The above components enhance the bonding strength between the substrate, transition layer, reinforcement layer, and surface layer, making the bond between the transition layer and the surface layer tighter while ensuring the wear resistance of the composite wear-resistant coating on the TC4 titanium alloy surface.

[0042] Specifically, the powder particle size of the WC particles is 50 to 150 μm, and the powder particle size of the TC4 particles is 50 to 120 μm.

[0043] The similar particle size of the WC and TC4 particles allows for a more uniform mixture. This allows for even coverage of the TC4 titanium alloy surface during laser powder feeding, and forms a uniform transition layer or surface layer after laser cladding, thus preventing uneven coatings that could lead to reduced wear resistance. In one embodiment of the present invention, the WC particles are spherical cast WC powder from Great Wall Zigong.

[0044] Specifically, the total thickness of the transition layer and the surface layer is 4 to 7 mm. In a specific embodiment of the present invention, the total thickness of the transition layer and the surface layer is 6 mm.

[0045] The present invention also provides a method for preparing a composite wear-resistant coating on the surface of a TC4 titanium alloy, which is used to prepare the composite wear-resistant coating on the surface of the TC4 titanium alloy, comprising the following steps:

[0046] Pretreatment: Clean the surface of TC4 titanium alloy, dry it and bake it to obtain TC4 titanium alloy substrate;

[0047] Weighing TC4 particles and WC particles: drying the TC4 particles and WC particles, weighing the TC4 particles and WC particles according to the ratio of the transition layer, and mixing them to obtain a transition layer powder; then weighing the TC4 particles and WC particles according to the ratio of the surface layer, and mixing them to obtain a surface layer powder;

[0048] First laser cladding: a protective gas is introduced to transport transition layer powder to the TC4 titanium alloy substrate, and the TC4 titanium alloy substrate is subjected to the first laser cladding to form a transition layer on the surface of the TC4 titanium alloy substrate to obtain a transition TC4 titanium alloy substrate;

[0049] Second laser cladding: A protective gas is introduced to transport the surface layer powder to the transition TC4 titanium alloy substrate, and the transition TC4 titanium alloy substrate is laser clad for the second time to form a surface layer on the surface of the transition layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0050] Laser cladding can produce coatings with excellent overall properties on substrate materials. It is primarily used for surface modification and repair of mechanical parts. It is an important method for effectively improving the wear resistance, corrosion resistance, and high-temperature oxidation resistance of component surfaces. Compared with other surface treatment technologies, it offers advantages such as high cooling rates, a low melting point between the coating and the substrate, minimal deformation, and a denser microstructure.

[0051] The method for preparing a composite wear-resistant coating on a TC4 titanium alloy surface involves several laser cladding steps to deposit TC4 and WC particles onto the TC4 titanium alloy surface, forming a WC / TC4 coating. The WC / TC4 coating is free of defects such as pores, porosity, or cracks, exhibits good interlayer bonding, and exhibits a metallurgical bond between the coating and the interface. In one embodiment, the WC / TC4 coating comprises three reinforcement layers, a top layer, and a transition layer, for a total of five layers.

[0052] The above-mentioned 5-layer WC / TC4 coating is similar to the WC / TC4 coating with only a surface layer and a transition layer, except that: 1. In the step of weighing TC4 particles and WC particles, TC4 particles and WC particles are weighed according to the ratio of each reinforcement layer, and mixed to obtain reinforcement layer powder, and the reinforcement layer powder of each layer is placed into the laser powder feeder respectively; 2. Between the first laser cladding and the second laser cladding steps, one or more reinforcement layer laser claddings are also included. The specific steps include: introducing protective gas, conveying reinforcement layer powder to the transition TC4 titanium alloy substrate through the laser powder feeder, and performing reinforcement layer laser cladding on the transition TC4 titanium alloy substrate to form a reinforcement layer on the surface of the transition layer, or performing another reinforcement layer laser cladding on the reinforcement layer to form another reinforcement layer on the surface of the reinforcement layer. In the second laser cladding step, the specific steps include: introducing protective gas, transporting surface layer powder to the TC4 titanium alloy substrate clad with the reinforcement layer through a laser powder feeder, and performing a second laser cladding on the surface of the reinforcement layer to form a surface layer on the surface of the reinforcement layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0053] Specifically, in the first laser cladding and the second laser cladding steps, the laser power is 2100-2300 W, the output continuous wavelength is 750-1070 nm, and the spot diameter is 1.2 mm-7 mm.

[0054] In one embodiment of the present invention, the laser cladding equipment is a TruDisk6006 laser cladding system manufactured by Trumpf. This system includes a Trumpf 6000W disk-type solid-state laser, a laser powder feeder, a chiller, a manipulator, a tilting turntable, a CNC machine tool, an internal hole cladding head, a cladding head, a motorized focusing lens, and other related components, as well as a complete system integration. The laser powder feeder uses a coaxial powder feeding method to deliver a mixed powder of TC4 and WC particles.

[0055] Specifically, in the first laser cladding and second laser cladding steps, the gas flow rate for conveying transition layer powder or surface layer powder is set to 4-6 L / min, the shielding gas is set to 9-10 L / min, the powder feeding rate of transition layer powder is 3.6-3.8 r / min, and the powder feeding rate of surface layer powder is 4.0-4.2 r / min. The shielding gas and the powder feeding gas of the laser powder feeder are argon and helium with a purity of 99.999%.

[0056] In a specific embodiment of the present invention, the air flow rate of the laser powder feeder is set to 6 L / min, the protective gas is set to 10 L / min, the powder feeding rate of the transition layer is 3.8 r / min, and the powder feeding rate of the surface layer is 4.2 r / min.

[0057] Specifically, in the pretreatment step, the step of cleaning the surface of the TC4 titanium alloy includes: polishing the surface of the TC4 titanium alloy and degreasing it with acetone; and then preheating it at 300° C. for 28 to 35 minutes.

[0058] Polishing the surface of TC4 titanium alloy can remove the surface oxide film, preventing it from affecting the cladding of the composite wear-resistant coating on the TC4 titanium alloy surface. Acetone can remove oil stains on the surface of TC4 titanium alloy, thereby reducing the risk of cracking or peeling of the coating. Preheating at 300℃ for 30 minutes can remove excess acetone and increase the temperature of the TC4 titanium alloy to facilitate laser cladding.

[0059] Example Group A

[0060] A method for preparing a composite wear-resistant coating on the surface of a TC4 titanium alloy, for preparing the composite wear-resistant coating on the surface of the TC4 titanium alloy, comprising the following steps:

[0061] Pretreatment: The surface of the TC4 titanium alloy was polished and degreased with acetone; then preheated at 300°C for 30 minutes to obtain a TC4 titanium alloy substrate;

[0062] Weighing TC4 particles and WC particles: Drying the TC4 particles and WC particles, weighing the TC4 particles and WC particles according to the ratio of the transition layer in Table 1, and mixing to obtain a transition layer powder; then weighing the TC4 particles and WC particles according to the ratio of the surface layer in Table 1, and mixing to obtain a surface layer powder; respectively placing the transition layer powder and the surface layer powder into a laser powder feeder;

[0063] First laser cladding: A protective gas is introduced, and a transition layer powder is delivered to the TC4 titanium alloy substrate through a laser powder feeder. The TC4 titanium alloy substrate is subjected to the first laser cladding to form a transition layer on the surface of the TC4 titanium alloy substrate, thereby obtaining a transition TC4 titanium alloy substrate.

[0064] Second laser cladding: protective gas is introduced, and surface layer powder is transported to the transition TC4 titanium alloy substrate through a laser powder feeder, and the transition TC4 titanium alloy substrate is laser clad for the second time to form a surface layer on the surface of the transition layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0065] The total thickness of the composite wear-resistant coating on the surface of TC4 titanium alloy is 6 mm.

[0066] Table 1 - Components and parameters

[0067] Example 4

[0068] A method for preparing a composite wear-resistant coating on a TC4 titanium alloy surface, used for preparing the composite wear-resistant coating on the TC4 titanium alloy surface, the composite wear-resistant coating on the TC4 titanium alloy surface comprising a transition layer, a first reinforcement layer, a second reinforcement layer, a third reinforcement layer and a surface layer, wherein the components of the transition layer and the surface layer are the same as those in Example 2, except that the method comprises the following steps:

[0069] Pretreatment: The surface of the TC4 titanium alloy was polished and degreased with acetone; then preheated at 300°C for 30 minutes to obtain a TC4 titanium alloy substrate;

[0070] Weigh TC4 particles and WC particles: dry the TC4 particles and WC particles, weigh TC4 particles and WC particles according to the ratio of the transition layer, and mix them to obtain transition layer powder; weigh TC4 particles and WC particles according to the ratio of the first reinforcement layer, and mix them to obtain first reinforcement layer powder; weigh TC4 particles and WC particles according to the ratio of the second reinforcement layer, and mix them to obtain second reinforcement layer powder; weigh TC4 particles and WC particles according to the ratio of the third reinforcement layer, and mix them to obtain third reinforcement layer powder; weigh TC4 particles and WC particles according to the ratio of the surface layer, and mix them to obtain surface layer powder; put the transition layer powder, the first reinforcement layer powder, the second reinforcement layer powder, the third reinforcement layer powder and the surface layer powder into the laser powder feeder respectively;

[0071] First laser cladding: A protective gas is introduced, and a transition layer powder is delivered to the TC4 titanium alloy substrate through a laser powder feeder. The TC4 titanium alloy substrate is subjected to the first laser cladding to form a transition layer on the surface of the TC4 titanium alloy substrate, thereby obtaining a transition TC4 titanium alloy substrate.

[0072] First reinforcement layer laser cladding: Shielding gas is introduced, and the first reinforcement layer powder is delivered to the transition TC4 titanium alloy substrate through a laser powder feeder. The first reinforcement layer laser cladding is performed on the TC4 titanium alloy substrate to form the first reinforcement layer on the surface of the transition layer.

[0073] Second reinforcement layer laser cladding: Shielding gas is introduced, and the second reinforcement layer powder is transported to the first reinforcement layer through the laser powder feeder. The second reinforcement layer laser cladding is performed on the TC4 titanium alloy substrate to form the second reinforcement layer on the surface of the transition layer.

[0074] Third reinforcement layer laser cladding: protective gas is introduced, and the third reinforcement layer powder is transported to the second reinforcement layer through the laser powder feeder, and the TC4 titanium alloy substrate is laser clad for the third reinforcement layer to form the third reinforcement layer on the surface of the transition layer;

[0075] Second laser cladding: protective gas is introduced, and the surface layer powder is transported to the third reinforcement layer through the laser powder feeder, and the transition TC4 titanium alloy substrate is laser clad for the second time to form a surface layer on the surface of the transition layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

[0076] Among them, in laser cladding, the laser power of the transition layer is 2300KW, the laser power of the first reinforcement layer, the second reinforcement layer, the third reinforcement layer and the surface layer is 2100KW, and the spot diameter is 5mm. The air flow rate of the laser powder feeder is set to 6L / min, the shielding gas is set to 10L / min, the powder feeding rate of the transition layer powder is 3.8r / min, the powder feeding rate of the first reinforcement layer powder, the second reinforcement layer powder and the third reinforcement layer powder is 4.0r / min, and the powder feeding rate of the surface layer powder is 4.2r / min, with a total thickness of 6mm. The powder size of the TC4 particles and the WC particles is the same as that in Example 2. The components of the composite wear-resistant coating on the surface of the TC4 titanium alloy are shown in Table 2.

[0077] Table 2-Components of composite wear-resistant coating on TC4 titanium alloy surface

[0078] The interface bonding between the composite wear-resistant coating on the surface of TC4 titanium alloy and the TC4 titanium alloy substrate of Examples 1 and 2 was observed, and the results are shown in Figures 1 and 2; the metallographic microstructure of Example 2 was observed, and the results are shown in Figures 3 and 4; the composite wear-resistant coating on the surface of TC4 titanium alloy prepared in Examples 1 to 4 was supported on a wear-resistant test block by laser cladding using TC4 titanium alloy as a cladding material, and a microhardness test was performed with a tempered TC4 titanium alloy sample block, and the friction and wear properties of the wear-resistant test blocks prepared in Examples 1 to 4, the tempered TC4 titanium alloy sample block and the alloy with hardness HRC50-50 were used. The microhardness test results are shown in Table 3, and the friction and wear performance results are shown in Table 4.

[0079] The conditions for friction and wear performance are load 30N, number of times 400 times, and sandpaper mesh size 400. Before the test, the surface of the wear-resistant test block after cladding is pretreated, and then weighed, and the original weight is recorded. The experiment is repeated five times, and it is weighed again before each experiment, and the weight after the experiment is recorded.

[0080] Table 3 - Microhardness test results

[0081] Microhardness testing reveals that the hardness of the TC4 titanium alloy substrate laser-clad without cladding material is not significantly altered compared to the hardness of the quenched and tempered TC4 titanium alloy sample, indicating that the thermal effects of laser cladding have no significant impact on the substrate's inherent hardness. However, after cladding with WC and TC4 particles, the average hardness exceeds 2700 Hv.

[0082] Table 4 - Friction and wear performance results

[0083] It can be seen from the results that the wear amount of the wear-resistant sample with the composite wear-resistant coating on the surface of the TC4 titanium alloy laser cladding is about 2.7 mg, the wear amount of the tempered TC4 titanium alloy sample is about 18.6 mg, and the wear amount of the alloy with a hardness of HRC50-50 is about 31.4 mg. The wear performance of the laser cladding wear-resistant coating is about 6 times that of the tempered TC4 titanium alloy sample and 10 times that of the alloy with a hardness of HRC50-50.

[0084] From Figures 1 and 2, it can be seen that there is metallurgical bonding between the interface of the composite wear-resistant coating on the surface of TC4 titanium alloy and the TC4 titanium alloy substrate. Moreover, through tensile tests and adhesion tests, the bonding strength of the laser cladding coating is greater than 300 MPa.

[0085] From Figures 3 and 4, it can be seen that the WC particles are evenly distributed, there are no defects such as holes, looseness, and cracks inside the coating, and the layers are well bonded.

[0086] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will be able to devise other specific embodiments of the present invention without inventive effort, and such equivalent variations or substitutions are intended to be encompassed within the scope of the claims of this application.

Claims

1. A composite wear-resistant coating on the surface of TC4 titanium alloy, characterized in that: It comprises a transition layer and a surface layer; the transition layer is attached to the surface of the TC4 titanium alloy by laser cladding, and the surface layer is attached to the transition layer by laser cladding; The raw materials of the transition layer include the following components by weight percentage: 70-90% TC4 particles and 10-30% WC particles; the raw materials of the surface layer include the following components by weight percentage: 50-70% TC4 particles and 30-50% WC particles.

2. The TC4 titanium alloy surface composite wear-resistant coating according to claim 1, characterized in that: It also includes one or more reinforcement layers, which are located between the transition layer and the surface layer. The raw materials of the reinforcement layer include the following components in weight percentage: 60-70% TC4 particles and 30-40% WC particles. The weight percentage of TC4 particles in the reinforcement layer is less than the weight percentage of TC4 particles in the transition layer, and the weight percentage of TC4 particles in the reinforcement layer is greater than the weight percentage of TC4 particles in the transition layer.

3. The TC4 titanium alloy surface composite wear-resistant coating according to claim 1, characterized in that: The powder particle size of the WC particles is 50 to 150 μm, and the powder particle size of the TC4 particles is 50 to 120 μm.

4. The TC4 titanium alloy surface composite wear-resistant coating according to claim 1, characterized in that: The total thickness of the transition layer and the surface layer is 4 to 7 mm.

5. A method for preparing a composite wear-resistant coating on the surface of a TC4 titanium alloy, for preparing the composite wear-resistant coating on the surface of a TC4 titanium alloy as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Pretreatment: cleaning the surface of TC4 titanium alloy, drying and baking to obtain TC4 titanium alloy substrate; Weighing TC4 particles and WC particles: drying the TC4 particles and WC particles, weighing the TC4 particles and WC particles according to the ratio of the transition layer, and mixing them to obtain transition layer powder; then weighing the TC4 particles and WC particles according to the ratio of the surface layer, and mixing them to obtain surface layer powder; First laser cladding: protective gas is introduced to transport transition layer powder to the TC4 titanium alloy substrate, and Performing a first laser cladding on the TC4 titanium alloy substrate to form a transition layer on the surface of the TC4 titanium alloy substrate to obtain a transition TC4 titanium alloy substrate; Second laser cladding: a protective gas is introduced to transport the surface layer powder to the transition TC4 titanium alloy substrate, and the transition TC4 titanium alloy substrate is laser clad for the second time to form a surface layer on the surface of the transition layer to obtain a composite wear-resistant coating on the surface of the TC4 titanium alloy.

6. The method for preparing a composite wear-resistant coating on the surface of TC4 titanium alloy according to claim 5, characterized in that: In the first laser cladding and the second laser cladding steps, the laser power is 2100-2300 W, the output continuous wavelength is 750-1070 nm, and the spot diameter is 1.2 mm-7 mm.

7. The method for preparing a composite wear-resistant coating on the surface of TC4 titanium alloy according to claim 5, characterized in that: In the first laser cladding and the second laser cladding steps, the gas flow rate for conveying transition layer powder or surface layer powder is set to 4-6 L / min, the shielding gas is set to 9-10 L / min, the powder feeding rate of transition layer powder is 3.6-3.8 r / min, and the powder feeding rate of surface layer powder is 4.0-4.2 r / min. The shielding gas and the powder feeding gas of the laser powder feeder are argon and helium with a purity of 99.999%.

8. The method for preparing a composite wear-resistant coating on the surface of TC4 titanium alloy according to claim 1, characterized in that: In the pretreatment step, the step of cleaning the surface of the TC4 titanium alloy includes: polishing the surface of the TC4 titanium alloy and degreasing it with acetone; and then preheating it at 300° C. for 28 to 35 minutes.

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