A method for laser cladding Ti-Al-Co eutectic composite reinforcing phase on titanium alloy

Abstract

This invention relates to the field of metal surface modification and high-temperature coating preparation technology, and particularly to a method for laser surface cladding of eutectic composite reinforcing phases of titanium alloys, comprising TiN, SiC, and ZrO. 2 Three different types of reinforcing phase powders were added to Ti-Al-Co powder to form alloy powders containing reinforcing phases, which were then pre-placed on the surface of titanium alloys to form a pre-coating. The pre-coating was then clad using a laser cladding machine under high-purity argon protection to obtain a titanium alloy with a eutectic cladding layer. Experimental analysis of the mechanical properties and high-temperature oxidation resistance of the Ti-Al-Co / TiN, Ti-Al-Co / SiC, and Ti-Al-Co / ZrO2 eutectic composite cladding layers generated by laser cladding revealed the effect of the eutectic structure on improving the plasticity and toughness of the composite cladding layer and the mechanism by which the reinforcing phase inhibits the growth of rutile TiO2 in the oxide film. This invention adds TiN, SiC, and ZrO2 to the Ti-Al-Co alloy coating material. 2 This further enhances the high-temperature oxidation resistance and anti-friction and wear resistance of the coating.

Description

A method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase on titanium alloys Technical Field

[0001] This invention relates to the field of metal surface modification and high-temperature coating preparation technology, and in particular to a method for laser surface cladding of Ti-Al-Co eutectic reinforcing phase on titanium alloys. Background Technology

[0002] With the continuous improvement of my country's aerospace industry's scientific and technological level, TC21 titanium alloy, characterized by high specific strength, good performance at medium and low temperatures, and excellent corrosion resistance, is often used as a structural material for key aircraft components in the aerospace field. However, due to the high-temperature conditions often encountered by aerospace components, the high-temperature oxidation resistance of TC21 titanium alloy decreases sharply, making it difficult to balance thermal strength and thermal stability. Furthermore, it suffers severe abrasive wear under dry friction conditions at room temperature. Therefore, developing and improving the surface properties of TC21 titanium alloy has become a crucial issue urgently needing to be addressed to expand the application range of titanium alloys. Currently, the mainstream treatment method is to modify and strengthen the metal surface. Laser cladding is a technique that improves surface properties by coating a specific alloy layer onto the substrate surface while maintaining the internal properties. With its rapid heating and cooling process, laser cladding results in a small heat-affected zone and a tight bond between the sample and the coating, and has gradually become one of the important technologies for surface coating preparation and modification strengthening.

[0003] Ti+Al intermetallic compounds outperform titanium alloys in all aspects. Ti+Al coatings on metal surfaces offer advantages such as high specific elastic modulus, high creep resistance and oxidation resistance, and low thermal expansion coefficient. They also exhibit good compatibility with titanium alloy substrates and are frequently used in research on next-generation lightweight high-temperature structural materials. However, the directionality and low symmetry of the intermetallic compound γ-TiAl result in poor room-temperature plasticity and toughness, as well as high brittleness, limiting the widespread application of Ti+Al coatings.

[0004] In recent years, novel anti-oxidation Ti-Al-X protective coatings have been developed, exhibiting good compatibility with titanium alloy substrates. By adding other elements to the TiAl coating without requiring excessive Al, the high-temperature oxidation resistance of titanium alloys can be improved, thus providing better protection. Furthermore, Ti-Al-X coatings are less brittle and have better plasticity than TiAl intermetallic compound coatings. Compared to nickel-based superalloys, their oxidation resistance temperature can reach over 900 °C, resulting in more significant application advantages. However, titanium alloy workpieces in the aerospace field often operate under more complex high-temperature conditions, requiring even superior surface high-temperature oxidation resistance and anti-friction and wear properties.

[0005] Currently, various ceramic powders have attracted widespread attention as coating materials due to their excellent corrosion resistance, wear resistance, and oxidation resistance, and have also shown broad prospects for industrial applications. In recent years, composite powder systems formed by mixing various high-melting-point hard ceramic materials such as carbides, nitrides, borides, oxides, and silicides with metal materials have developed rapidly. Therefore, in order to further improve the comprehensive mechanical properties of coatings, it is necessary to add ceramic powders such as nitrides, carbides, and oxides to Ti-Al-X based powders. The key is to rationally adjust the content ratio of ceramic powder components to further control the coating microstructure, acting as a second phase to obtain higher wear resistance, hardness, and oxidation resistance, thereby giving the coating a wider range of applications. Summary of the Invention

[0006] This invention addresses the problems of low friction and wear performance at room temperature, a sharp drop in high-temperature oxidation resistance, and poor thermal stability in titanium alloys. It provides a method for laser cladding of titanium alloys with a Ti-Al-Co eutectic composite reinforcing phase. This invention introduces Co into a TiAl-based coating and adds three different types of reinforcing phases—TiN, SiC, and ZrO2—to the Ti-Al-Co alloy coating. It utilizes the high-temperature stability and wear resistance of TiN, the high hardness and oxidation resistance of SiC, and the excellent high-temperature strength and wear resistance of ZrO2. A cladding layer with high wear resistance and high-temperature oxidation resistance is prepared on a TC21 titanium alloy substrate, and the microstructure evolution law and behavior are elucidated.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A method for laser cladding of Ti-Al-Co eutectic composite reinforcing phases onto titanium alloys includes the following steps:

[0009] Three different types of reinforcing phase powders, TiN, SiC, and ZrO2, are added to Ti-Al-Co powder to form alloy powder containing reinforcing phases, which are then pre-placed on the surface of titanium alloy to form a pre-coating.

[0010] The pre-coated layer is clad using a laser cladding machine under the protection of high-purity argon gas to obtain a titanium alloy with a eutectic cladding layer.

[0011] Furthermore, the mass fractions of the three types of reinforcing phases, TiN, SiC, and ZrO2, are 2wt.%, 4wt.%, 6wt.%, 8wt.%, 10wt.%, and 12wt.%, respectively.

[0012] Furthermore, the mass ratio of Ti:Al:Co in the eutectic cladding layer is 25.0%~45%:32.5%~52.5%:22.5%;

[0013] After mixing the eutectic component powder according to the calculated component ratio, grind it to ensure that the powder is fully mixed.

[0014] The ground powder was placed in a vacuum drying oven at 100°C to dry it and remove the moisture. The powder was then evenly coated onto the sample surface with a thickness of 1 mm.

[0015] Furthermore, the high-purity argon gas flow rate of the laser cladding protection box is 10-20 L / min, the spot diameter is 1-5 mm, the working wavelength is 1070 nm, and the defocusing amount is 10-30 mm; preferably, the high-purity argon gas flow rate is 15 L / min, the spot diameter is 3 mm, the working wavelength is 1070 nm, and the defocusing amount is 20 mm.

[0016] Using the method of the present invention, the Ti-Al-Co / TiN eutectic composite cladding layer obtained has good forming quality and no obvious defects. The surface of the cladding layer shows wrinkles as the nitride content increases.

[0017] Using the method of the present invention, the addition of an appropriate amount of carbide (<10wt.%) in the obtained Ti-Al-Co / SiC eutectic composite cladding layer will improve the wettability of the Ti-Al-Co eutectic composite cladding layer and the TC21 titanium alloy substrate, and enhance the compatibility between the cladding layer and the substrate.

[0018] Using the method of the present invention, the macroscopic morphology of the obtained Ti-Al-Co / ZrO2 eutectic composite cladding layer is dark metallic luster. An appropriate amount (<8wt.%) of oxide reinforcing phase can promote the absorption rate of laser irradiation energy of the Ti-Al-Co eutectic composite cladding layer and reduce the tendency of crack initiation.

[0019] Furthermore, since the gases generated by the thermal decomposition of the adhesive can easily contaminate the surface of the titanium alloy, leading to defects in the cladding layer, this invention does not use any adhesive.

[0020] The self-fluxing powder Co in this invention possesses high-temperature oxidation resistance and exhibits similar compatibility, elastic modulus, thermal conductivity, and linear expansion coefficient with the titanium alloy sample, which facilitates the formation of a metallurgical bond between the cladding layer and the substrate. Therefore, introducing Co into a Ti+Al-based coating to prepare a Ti-Al-Co-based coating can combine the advantages of TiAl-based alloys and eutectic alloys, improving toughness and reducing brittleness.

[0021] TiN reinforced phase: A metal nitride with a melting point (2950℃) higher than other transition zone metals, and a density (5.22 g / cm³). 3 It has low calorific value, high electrical conductivity, high thermal conductivity, and high hardness, as well as good stability, wear resistance, and corrosion resistance. Adding TiN to the Ti-Al-Co eutectic cladding layer can effectively utilize the excellent plasticity and toughness of the eutectic structure to improve problems such as high hardness and brittleness.

[0022] SiC reinforcement phase: It has advantages such as excellent high-temperature strength, oxidation resistance, corrosion resistance and low cost. Adding SiC reinforcement phase to Ti-Al-Co eutectic cladding layer can significantly reduce residual stress in the coating, promote the formation of new compounds with both metallic and ceramic properties, and improve the overall performance of the cladding layer.

[0023] ZrO2 reinforced phase: It has excellent high-temperature strength, oxidation resistance, and high hardness and wear resistance, and is often used in the preparation of cladding layers. ZrO2 reinforced phase can significantly improve crack defects caused by residual stress inside the cladding layer. At the same time, the stress-induced phase transformation toughening and dispersion toughening effect of adding ZrO2 to the eutectic coating improves the surface toughness and wear resistance of the cladding layer.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) Through experimental analysis of the mechanical properties and high-temperature oxidation resistance of Ti-Al-Co / TiN, Ti-Al-Co / SiC and Ti-Al-Co / ZrO2 eutectic composite cladding layers generated by laser cladding, the eutectic structure was found to enhance the plasticity and toughness of the composite cladding layer and to inhibit the growth of rutile TiO2 in the oxide film.

[0026] (2) The laser cladding method for Ti-Al-Co eutectic composite reinforcing phase provided by the present invention, with the appropriate addition of TiN, forms a eutectic cladding layer oxide film mainly composed of TiO2 and Al2O3, which prevents oxygen atoms from diffusing into the composite coating and plays an anti-oxidation role. TiN as a reinforcing phase can promote the transformation of intergranular eutectic Al3Ti+Al9CoTi2 phase to AlCo2Ti, and with undissolved TiN particles as the core and (Ti,Al)N complex solid solution as the ring phase, the core-ring structure can inhibit grain growth and improve the wettability of the liquid molten pool and the toughness of the cladding layer.

[0027] (3) The laser cladding method for Ti-Al-Co eutectic composite reinforcing phase provided by the present invention can increase the activity of Al element by adding an appropriate amount of SiC, inhibit the growth of TiO2, and increase the density of Al2O3 oxide film. As a reinforcing phase, SiC can promote the precipitation of Al3Ti+Al9Co2 eutectic phase between crystals. The clear interface between TiC phase and substrate phase (TiSi2, TiAl) is conducive to the transfer of residual stress in cladding layer from substrate phase to reinforcing phase. At the same time, the obvious dislocations at TiSi2 / TiAl interface can improve the strength and hardness of cladding layer.

[0028] (4) The laser cladding method for Ti-Al-Co eutectic composite reinforcing phase provided by the present invention, with an appropriate increase in ZrO2, allows Zr elements to exist in the cladding layer as ZrCo2Al phase, promoting an increase in the precipitation of dense Al2O3 and making the oxide film structure more compact. When ZrO2 is used as the reinforcing phase, the O atoms released from the melt decomposition cause the cladding layer to undergo a high-temperature oxidation reaction, promoting the dissociation of the eutectic Al3Ti+Al9Co2 phase and the precipitation of Ti5Al3O2 phase, thereby improving the high-temperature oxidation resistance of the cladding layer. Attached Figure Description

[0029] Figure 1 shows the macroscopic morphology of Ti-Al-Co / TiN eutectic cladding layers with different mass fractions;

[0030] In the figure, (a) 2 wt.% TiN, (b) 4 wt.% TiN, (c) 6 wt.% TiN, (d) 8 wt.% TiN, (e) 10 wt.% TiN, (f) 12 wt.% TiN.

[0031] Figure 2 shows the macroscopic morphology of Ti-Al-Co / SiC eutectic cladding layers with different mass fractions;

[0032] In the figure, (a) 2 wt.% SiC, (b) 4 wt.% SiC, (c) 6 wt.% SiC, (d) 8 wt.% SiC, (e) 10 wt.% SiC, (f) 12 wt.% SiC.

[0033] Figure 3 shows the macroscopic morphology of Ti-Al-Co / ZrO2 eutectic cladding layers with different mass fractions;

[0034] In the figure, (a) 2 wt.% ZrO2, (b) 4 wt.% ZrO2, (c) 6 wt.% ZrO2, (d) 8 wt.%ZrO2, (e) 10 wt.% ZrO2, (f) 12 wt.% ZrO2.

[0035] Figure 4 shows the oxidation kinetics curves of TC21 titanium alloy, Ti-Al-Co cladding layer and Ti-Al-Co / TiN eutectic cladding layer prepared in Examples 1-6 at 850℃.

[0036] Figure 5 shows the oxidation kinetics curves of TC21 titanium alloy, Ti-Al-Co cladding layer and Ti-Al-Co / SiC eutectic cladding layer prepared in Examples 1-6 at 850℃.

[0037] Figure 6 shows the oxidation kinetics curves of TC21 titanium alloy, Ti-Al-Co cladding layer and Ti-Al-Co / ZrO2 eutectic cladding layer prepared in Examples 1-6 at 850℃. Detailed Implementation Methods

[0038] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0039] I. Material composition, proportions, and cladding layer preparation: Example 1

[0040] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0041] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, is 2 wt.%.

[0042] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0043] (4) The ground powder was placed in a vacuum drying oven and dried at 100°C to remove moisture. Example 2

[0044] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0045] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, was 4 wt.%.

[0046] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0047] (4) The ground powder was placed in a vacuum drying oven and dried at 100°C to remove moisture. Example 3

[0048] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0049] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, was 6 wt.%.

[0050] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0051] (4) The ground powder was placed in a vacuum drying oven and dried at 100°C to remove moisture. Example 4

[0052] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0053] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, was 8 wt.%.

[0054] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0055] (4) The ground powder was placed in a vacuum drying oven and dried at 100°C to remove moisture. Example 5

[0056] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0057] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, was 10 wt.%.

[0058] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0059] (4) The ground powder was placed in a vacuum drying oven and dried at 100°C to remove moisture. Example 6

[0060] (1) The composition of the Ti-Al-Co eutectic cladding layer, with a mass ratio of Ti:Al:Co of 25.0%:52.5%:22.5%;

[0061] (2) The mass fraction of the three types of reinforcing phases, TiN, SiC, and ZrO2, was 12 wt.%.

[0062] (3) Grind the prepared eutectic component powder for 1 hour to ensure thorough mixing of the powder;

[0063] (4) The ground powder is placed in a vacuum drying oven and dried at 100°C to remove moisture from the powder.

[0064] II. Preparation of Laser Cladding Coatings

[0065] The laser cladding powder materials provided in Examples 1-6 were pre-placed on the surface of TC21 titanium alloy and subjected to laser cladding treatment. The specific coating preparation steps are as follows:

[0066] (1) Cut the titanium alloy block into a rectangular sample of 30mm×15mm×8mm, polish it with 200# sandpaper to remove the oxide layer on the sample surface, and use it after ultrasonic cleaning with alcohol as a medium.

[0067] (2) The obtained dry mixed powder is uniformly coated on the surface of the sample to form a pre-coated layer with a powder thickness of 1 mm.

[0068] (3) The laser cladding machine was used to perform cladding under the protection of high-purity argon gas. The flow rate of high-purity argon gas was 15L / min, the spot diameter was 3mm, the working wavelength was 1070nm, and the defocusing amount was 20mm.

[0069] (4) The cladding layer is processed, the macroscopic morphology is observed, the microstructure is analyzed, and the changes in cross-sectional hardness, surface wear resistance and high-temperature oxidation resistance are tested.

[0070] III. Macroscopic Surface Morphology Analysis

[0071] Figure 1 shows the macroscopic morphology of Ti-Al-Co / TiN eutectic cladding layers with different mass fractions. As the TiN content increases, the surface of the cladding layer becomes rougher, exhibiting minute ripples, and the color gradually shifts towards a golden yellow. The best forming quality is achieved when the TiN mass fraction is 2 wt.%. This is because the flow stirring force of the molten pool increases with the increase of the TiN content during the cladding process, intensifying the convection motion of the melt within the molten pool.

[0072] Figure 2 shows the macroscopic morphology of Ti-Al-Co / SiC eutectic cladding layers with different mass fractions. As the SiC content increases, the surface initially becomes smoother, followed by the gradual appearance of metal particle splashes. When the TiN mass fraction is 4 wt.% and 6 wt.%, the surface is smooth and flat, indicating that an appropriate increase in SiC content can improve the surface smoothness of the cladding layer.

[0073] Figure 3 shows the macroscopic morphology of Ti-Al-Co / ZrO2 eutectic cladding layers with different mass fractions. As the ZrO2 content increases, the number of metal particles on the cladding layer surface increases, and overheating occurs on the cladding layer surface when the ZrO2 content is 12 wt.%.

[0074] The addition of different types of hard reinforcing phases has a significant impact on the morphology of the cladding layer. The increase in TiN content promotes the Marangoni effect, resulting in a wavy effect. The Si element in the Ti-Al-Co / SiC eutectic cladding layer can improve the bonding strength between the cladding layer and the TC21 titanium alloy matrix by lowering the melting point of the molten pool, and the surface smoothness of the cladding layer is enhanced. The Ti-Al-Co / ZrO2 eutectic cladding layer has fine metal particles on its surface. The increase in ZrO2 content intensifies the flow and stirring of the molten pool, ultimately causing a splashing effect.

[0075] IV. Microstructure Analysis

[0076] The Ti-Al-Co / TiN eutectic cladding layer of TiN forms a good metallurgical bond with the TC21 titanium alloy. The microstructure of the cladding layer consists of blocky eutectic phases. With increasing TiN content, the black blocky phase decreases, the dendritic phase increases, the gray blocky phase increases, and the intergranular eutectic phase decreases. TiN, as a reinforcing phase, can promote the transformation of the intergranular eutectic Al3Ti+Al9CoTi2 phase to AlCo2Ti. Furthermore, the core-ring structure with undissolved TiN particles as the core and the (Ti,Al)N complex solid solution as the ring phase can inhibit grain growth and improve the wettability of the molten pool and the toughness of the cladding layer.

[0077] The Ti-Al-Co / SiC eutectic cladding layer of SiC consists of a gray phase, a black granular phase, a dark gray stripe phase, and an intergranular eutectic phase. With increasing SiC content, the gray columnar crystals transform into large-area clustered phases, while the intergranular eutectic phase gradually decreases. The short, dispersed dark gray stripe phase and the dendritic black granular phase at the bottom of the cladding layer both increase. When the SiC content is 6 wt.%, the intergranular eutectic phase is replaced by the gray clustered phase. SiC, as a reinforcing phase, promotes the precipitation of the intergranular Al3Ti+Al9Co2 eutectic phase. The clear interface between the TiC phase and the substrate phases (TiSi2, TiAl) facilitates the transfer of residual stress from the substrate phase to the reinforcing phase in the cladding layer. Simultaneously, the significant dislocations at the TiSi2 / TiAl interface improve the strength and hardness of the cladding layer.

[0078] When the ZrO2 content is below 6 wt.%, the Ti-Al-Co / ZrO2 eutectic cladding layer mainly consists of black dendritic crystals, gray blocky crystals, and intergranular eutectic phases. When the ZrO2 content reaches 6 wt.%, the microstructure becomes significantly finer and denser with increasing ZrO2 content. The cladding layer mainly consists of black dendritic crystals and white intergranular phases. The black dendritic crystals are distributed perpendicular to the surface of the TC21 titanium alloy substrate, exhibiting a clear directionality. When an appropriate amount of ZrO2 acts as a reinforcing phase, the O atoms released from the melt decomposition promote a high-temperature oxidation reaction in the cladding layer, facilitating the dissociation of the eutectic Al3Ti+Al9Co2 phase and the precipitation of the Ti5Al3O2 phase, thus improving the high-temperature oxidation resistance of the cladding layer.

[0079] V. Performance Testing

[0080] 1. Analysis of wear resistance of eutectic cladding layer

[0081] Friction and wear experiments were conducted on Examples 1-6 using a CFT-1 comprehensive material testing instrument. During the friction and wear process, the Si3N4 ceramic balls were pressed into the substrate surface under a vertical load, resulting in significant plastic deformation, and then moved back and forth at high speed in the horizontal direction. The test parameters were: normal load 10N, friction pair consisting of silicon nitride balls with a diameter of 3mm, reciprocating sliding speed of the friction pair 100mm / s, wear time 30min, and wear track length 5mm.

[0082] Compared with the Ti-Al-Co / TiN cladding layers prepared in Examples 1-6, the TC21 substrate surface showed more severe impact from grinding balls after dry sliding friction and wear experiments. The wear mechanism was mainly adhesive wear, accompanied by abrasive wear. The friction and wear morphology of the Ti-Al-Co / TiN cladding layer was smoother, indicating that the cladding layer had high bonding strength with the substrate and good wear resistance. The 0 wt.%, 2 wt.%, and 4 wt.% TiN cladding layers mainly consisted of TiAl, Al3Ti, and Al3Ti+Al9Co2, with low N content. The N element did not precipitate in the form of compounds but was dissolved in the eutectic Al3Ti+Al9Co2 of the cladding layer, and its wear mechanism was adhesive wear. As the TiN content gradually increased to 10 wt.%, the N element content increased, forming a hard TiN phase with Ti, which improved the surface wear resistance. When the content reaches 12 wt.%, the excessive amount of hard TiN phase leads to increased brittleness and hardness, resulting in surface spalling and wear, severe plastic deformation of the cladding layer, and intensified friction and wear. Comprehensive analysis shows that the 8 wt.% TiN cladding layer exhibits the best wear resistance, approximately 2.22 times that of the substrate.

[0083] Microscopic analysis of the worn surface after dry sliding friction and wear experiments of the Ti-Al-Co / SiC cladding layer revealed that the cladding layer with a small amount of SiC (2 wt.%, 4 wt.%) exhibited shallow furrows and flaky adhesions on its worn surface. The sliding of the Si3N4 friction pair on the cladding layer surface created a micro-cutting effect, inducing plastic deformation. Simultaneously, the formation of hard phases TiC and TiSi2 mitigated the degree of adhesive wear, but the wear mechanism remained adhesive wear. With further increases in SiC content, TiC and TiSi2 peeled off during the Si3N4 cutting process and were incorporated into the grinding process of the cladding layer, resulting in severe plastic deformation, severe adhesive wear, and abrasive wear, thus reducing its wear resistance. Overall, the 8 wt.% SiC cladding layer showed the best wear resistance, approximately 3.06 times that of the substrate.

[0084] Analysis of the microstructure of the worn surface after dry sliding friction and wear experiments on Ti-Al-Co / ZrO2 cladding layers revealed that the wear mechanism of the Ti-Al-Co / ZrO2 eutectic composite cladding layer with 2wt.%-8wt.% ZrO2 was abrasive wear, with decreased plasticity and toughness, increased brittleness, and crack formation. The Ti-Al-Co / ZrO2 cladding layer with 10wt.%-12wt.% ZrO2 exhibited severe adhesive wear and abrasive wear. The amount of Al3Ti5O2 precipitation increased with increasing ZrO2 content, showing a significant dispersion strengthening effect and a significant increase in the microhardness of the cladding layer. Overall, the 6wt.% ZrO2 cladding layer exhibited the best wear resistance, approximately 1.41 times that of the matrix.

[0085] 2. Analysis of the antioxidant properties of the eutectic cladding layer

[0086] The oxidation behavior of TC21 titanium alloy and the eutectic reinforced cladding layers prepared in Examples 1-6 was determined using a high-temperature energy-saving box furnace (model SX-GO1173) after oxidation at 850℃ for 120 hours. To reduce experimental error, each sample underwent three oxidation weight gain tests, and the average of the three oxidation weight gains was taken as the oxidation weight gain of the sample. The oxidation weight gain of the crucible and sample was measured every 24 hours using an electronic balance with an accuracy of 0.0001 mg, and the measurements were repeated five times to obtain the final oxidation kinetic curve.

[0087] Figure 4 shows the oxidation kinetics curves of TC21 titanium alloy and the Ti-Al-Co / TiN eutectic cladding layers prepared in Examples 1-6 at 850℃. The oxidation weight gain of the cladding layers follows a parabolic law. The TC21 titanium alloy substrate is significantly oxidized, exhibiting the fastest oxidation weight gain rate and the worst oxidation resistance. As the amount of TiN in the cladding layer increases, the oxidation growth rate of the coating slows down, the weight gain per unit area decreases, and the oxidation resistance of the cladding layer significantly declines. The oxide film of the Ti-Al-Co / TiN eutectic cladding layer is mainly composed of TiO2 and Al2O3, which prevents oxygen atoms from diffusing into the composite coating and plays an anti-oxidation role. Among them, the 6 wt.% TiN cladding layer has the smallest weight gain per unit area (0.41 mg / cm2), which is 8 times higher than that of the TC21 substrate, demonstrating excellent high-temperature oxidation resistance.

[0088] Figure 5 shows the oxidation kinetics curves of TC21 titanium alloy and the Ti-Al-Co / SiC eutectic cladding layers prepared in Examples 1-6 at 850℃. The TC21 titanium alloy matrix was significantly oxidized, exhibiting the fastest oxidation weight gain rate and the worst high-temperature oxidation resistance. Adding SiC to the cladding layer significantly slowed the oxidation growth rate, reduced weight gain, and improved oxidation resistance. When the SiC content in the cladding layer was below 6 wt.%, the improvement in oxidation resistance was relatively small; when the SiC content was above 6 wt.%, the improvement in oxidation resistance was substantial, but when it exceeded 12 wt.%, the oxidation resistance tended to decrease. The cladding layer exhibited the best oxidation resistance when the SiC content was 10 wt.%, representing a 7.53-fold improvement compared to the matrix.

[0089] The oxide film of the Ti-Al-Co / SiC eutectic cladding layer mainly consists of an outer oxide film of TiO2+Al2O3+ composite oxide, a middle oxide film of TiO2+Al2O3, and an inner oxide film of AlCo2Ti+TiC+Ti5Si3. The appropriate addition of SiC can increase the activity of Al, inhibit the growth of TiO2, and thus increase the density of the Al2O3 oxide film.

[0090] Figure 6 shows the oxidation kinetics curves of TC21 titanium alloy, Ti-Al-Co cladding layer, and Ti-Al-Co / ZrO2 eutectic cladding layer prepared in Examples 1-6 at 850℃. The TC21 titanium alloy substrate showed the fastest oxidation weight gain rate, severe surface oxidation, and the worst high-temperature oxidation resistance. The Ti-Al-Co cladding layer showed the second-best oxidation resistance, with a 3.57-fold improvement compared to the substrate. Adding ZrO2 to the cladding layer significantly slowed down the oxidation growth rate and reduced the weight gain. However, when the ZrO2 content was too high, macroscopic cracks and pores appeared in the cladding layer, accelerating the oxidation process and increasing the oxidation weight gain. The cladding layer exhibited the best oxidation resistance when the ZrO2 content was 6 wt.%, a 13.04-fold improvement compared to the substrate. The oxide film of the Ti-Al-Co / ZrO2 eutectic cladding layer mainly consists of an outer oxide film of TiO2 + Al2O3 (minor) + composite oxide, a middle oxide film of TiO2 + Al2O3, and an inner oxide film of Co2Ti + AlCo2Ti. The increase of the ZrO2 reinforcing phase allows Zr elements to exist in the cladding layer as the ZrCO2Al phase, promoting an increase in the precipitation of dense Al2O3 and resulting in a more compact oxide film structure.

[0091] This invention adds TiN, SiC, and ZrO2 to the Ti-Al-Co alloy coating material to further improve the high-temperature oxidation resistance and anti-friction and wear performance of the coating.

[0092] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, changes can be made without departing from the spirit of the present invention.

Claims

1. A method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase onto titanium alloys, characterized in that, The method is as follows: three different types of reinforcing phase powders, TiN, SiC and ZrO2, are added to Ti-Al-Co powder to form an alloy powder containing reinforcing phases, and then pre-placed on the surface of the titanium alloy to form a pre-coating. The pre-coated layer is clad using a laser cladding machine under the protection of high-purity argon gas to obtain a titanium alloy with a eutectic cladding layer; wherein the mass ratio of Ti:Al:Co in the Ti-Al-Co powder is 25.0%~45%:32.5%~52.5%:22.5%.

2. The method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase onto titanium alloys according to claim 1, characterized in that: The mass fractions of the three reinforcing phases TiN, SiC, and ZrO2 are each independently selected from 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.%, 10 wt.%, and 12 wt.%.

3. The method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase onto titanium alloys according to claim 1, characterized in that: After grinding and mixing the eutectic component powder, it is placed in a vacuum drying oven and dried at 100°C to remove moisture from the powder. The powder is then uniformly coated onto the sample surface with a thickness of 1 mm.

4. The method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase onto titanium alloys according to claim 1, characterized in that: The high-purity argon gas flow rate of the laser cladding protection box is 10-20L / min, the spot diameter is 1-5mm, the working wavelength is 1070nm, and the defocusing amount is 10-30mm.

5. The method for laser cladding of Ti-Al-Co eutectic composite reinforcing phase onto titanium alloys according to claim 4, characterized in that: The laser cladding protective box has a high-purity argon gas flow rate of 15L / min, a spot diameter of 3mm, a working wavelength of 1070nm, and a defocusing amount of 20mm.

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