Preparation method and application of titanium nitride coating on surface of titanium alloy

Abstract

The invention discloses a preparation method and application of a titanium nitride coating on the surface of a titanium alloy. The preparation method of the titanium nitride coating comprises the following steps that titanium nitride powder is subjected to plasma cladding, and the titanium nitride coating is prepared on the surface of a titanium base material; the current of the plasma cladding is 80 to 160A. According to the method, titanium nitride powder and the surface of the titanium base material are subjected to sufficient element diffusion through a plasma cladding method under specific conditions, and a compact coating which is free of cracks and holes and has excellent bonding performance is formed. And the compatibility problem possibly caused by a multi-component cladding material is avoided, and the purity and performance of the coating are ensured. Moreover, the prepared titanium nitride coating has the characteristics of high hardness and low friction coefficient, the service life of a part in a high-friction environment can be effectively prolonged, and the prepared titanium material and structural member have wide application in the fields of aerospace, precision machinery or high-end equipment manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of surface engineering, and in particular relates to a preparation method and application of a titanium nitride coating on the surface of a titanium alloy. Background Art

[0002] Titanium materials, especially titanium alloys, have been widely used in aerospace, high-end equipment manufacturing and other fields due to their low density, high specific strength, excellent toughness and fatigue resistance. However, as the application scenarios expand from static load-bearing structures to dynamic moving parts, the inherent defects of titanium alloys, such as insufficient high-temperature oxidation ability and poor wear resistance, have become increasingly prominent, seriously affecting their service life in high-friction environments. Therefore, improving the wear resistance of titanium alloys under harsh working conditions has become a key technical challenge in their actual engineering applications.

[0003] At present, preparing wear-resistant metal ceramic coating on the surface of titanium alloy is an effective means to improve its service performance. Among them, traditional plasma spraying technology has made certain progress in coating preparation, but its coating bonding strength is low, and the microstructure is prone to pores and cracks, which limits its application in harsh environments. In addition, the existing coating preparation technology is difficult to achieve a dense, crack-free wear-resistant coating with a thickness of more than 1mm, which is difficult to meet the needs of high-load and long-life working conditions.

[0004] Therefore, there is an urgent need for a method that uses an efficient cladding process to prepare a coating with high bonding strength, no cracks, dense and uniform coating and excellent wear resistance on the surface of titanium alloy, so as to improve the service life of titanium alloy in high friction environment and expand its engineering application under complex working conditions. Summary of the invention

[0005] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a method for preparing a titanium nitride coating. The coating prepared by this method has the characteristics of high bonding strength, no cracks, dense uniformity and high wear resistance, thereby improving the service life of the titanium substrate in a high friction environment.

[0006] A second object of the present invention is to provide a titanium material.

[0007] A third object of the present invention is to provide a structural member.

[0008] A fourth object of the present invention is to provide an application of the above-mentioned titanium material or the above-mentioned structure.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A first aspect of the present invention provides a method for preparing a titanium nitride coating, comprising the following steps: subjecting titanium nitride powder to plasma cladding to prepare a titanium nitride coating on the surface of a titanium substrate; the current of the plasma cladding is 80 to 160A.

[0011] The inventive concept of the present invention: The present invention prepares a wear-resistant titanium nitride coating on the surface of a titanium substrate through plasma cladding technology under specific conditions, thereby significantly improving its wear resistance and service life. At the same time, the high energy input of plasma cladding allows sufficient element diffusion between the titanium nitride powder and the substrate to form a dense coating without cracks, holes and tight bonding, overcoming the problem of pores and cracks that are easily generated in traditional thermal spraying. In addition, combined with the high temperature, rapid solidification and excellent coating forming ability of plasma cladding, not only the wear resistance of the titanium substrate is improved, but also the toughness of the coating is optimized through the high hardness of titanium nitride and the moderate ductility of α-Ti, avoiding brittle fracture, thereby improving the comprehensive service performance of the coating and meeting the industrial application requirements of high-performance coatings.

[0012] In some embodiments of the present invention, the oxygen content of the titanium nitride powder is ≤500 ppm; for example, it can be any value of 500 ppm, 300 ppm, 100 ppm or 0 ppm, or a range between any two values.

[0013] In some embodiments of the present invention, the purity of the titanium nitride powder is ≥99.9%; for example, it can be any value among 99.9%, 99.95%, 99.99% or 100%, or a range between any two values.

[0014] The use of titanium nitride powder with higher purity is beneficial to ensure the purity and performance of the coating, while forming a good metallurgical bonding interface with the titanium substrate, with excellent bonding strength and durability.

[0015] In some embodiments of the present invention, the titanium nitride powder comprises the following components in atomic percentage: 48.50-51.50% Ti and 48.50-51.50% N.

[0016] In some specific embodiments of the present invention, the titanium nitride powder also includes inevitable impurities, and the content of the inevitable impurities is ≤0.05% by mass; for example, it can be any value among 0.05%, 0.03% or 0.01%, or a range value between any two of them.

[0017] In some embodiments of the present invention, the average particle size of the titanium nitride powder is 50-105 μm; for example, it can be any value among 50 μm, 70 μm, 90 μm, 100 μm or 105 μm, or a range between any two values.

[0018] In some embodiments of the present invention, the titanium substrate comprises a pure titanium substrate or a titanium alloy substrate; in some specific embodiments of the present invention, the titanium substrate is selected from a titanium alloy substrate. More specifically, the titanium alloy substrate is selected from a dual-phase titanium alloy substrate containing an α phase and a β phase.

[0019] In some embodiments of the present invention, the titanium substrate is selected from Ti6Al4V titanium alloy.

[0020] In some embodiments of the present invention, the plasma cladding adopts a synchronous powder feeding method.

[0021] In the present invention, synchronous powder feeding refers to a method in which, during the plasma cladding process, titanium nitride powder is directly fed into the molten pool while the plasma arc forms a surface molten pool. Specifically, unlike the pre-set powder method, the plasma cladding synchronous powder feeding process can achieve multi-pass uniform overlap, the coating molten pool lasts longer during the preparation process, and a good metallurgical bond can be formed between the substrate and the coating, thereby greatly improving the mechanical properties of the coating. The method of the present invention adopts synchronous powder feeding technology to directly introduce titanium nitride powder into the cladding process, fully integrate it with the titanium alloy substrate, and form a dense and wear-resistant coating composed of phases such as titanium nitride and α-Ti crystals; and, through the plasma cladding synchronous powder feeding process, large-area coatings can be efficiently prepared, overcoming the shortcomings of the pre-set powder method and meeting the actual needs of large-scale industrial production.

[0022] In some embodiments of the present invention, the powder feeding rate of the synchronous powder feeding is 1.0 to 5.0 g / min; in some specific embodiments of the present invention, the powder feeding rate of the synchronous powder feeding is 1.5 to 4.0 g / min; in some more specific embodiments of the present invention, the powder feeding rate of the synchronous powder feeding is 2.0 to 3.0 g / min.

[0023] By adjusting the powder feeding rate, it is beneficial to obtain a titanium nitride coating with more stable performance.

[0024] In some embodiments of the present invention, the powder feeding gas flow rate of the synchronous powder feeding is 3.0-6.0 L / min; in some specific embodiments of the present invention, the powder feeding gas flow rate of the synchronous powder feeding is 3.5-5.0 L / min.

[0025] In some embodiments of the present invention, the ion gas for plasma cladding is selected from pure argon; the purity of the pure argon is ≥ 99.99%; for example, it can be any value among 99.99%, 99.995%, 99.999% or 100%, or any range between the two.

[0026] In some embodiments of the present invention, the ion gas flow rate of the plasma cladding is 0.5 to 3.0 L / min; in some specific embodiments of the present invention, the ion gas flow rate of the plasma cladding is 0.8 to 2.0 L / min; in some more specific embodiments of the present invention, the ion gas flow rate of the plasma cladding is 1.0 to 1.5 L / min.

[0027] In some embodiments of the present invention, the cladding rate of the plasma cladding is 1.0 to 3.0 mm / s; in some specific embodiments of the present invention, the cladding rate of the plasma cladding is 1.2 to 2.5 mm / s; in some more specific embodiments of the present invention, the cladding rate of the plasma cladding is 1.5 to 2.0 mm / s.

[0028] In some embodiments of the present invention, the current of the plasma cladding is 90-150A; in some specific embodiments of the present invention, the current of the plasma cladding is 100-140A; for example, it can be any value among 100, 110, 120, 130 or 140 or a range between any two of them.

[0029] In some embodiments of the present invention, the distance between the nozzle of the plasma cladding device and the surface of the titanium substrate is 8.0 to 12.0 mm; for example, it may be 9.0 to 10.0 mm.

[0030] In some embodiments of the present invention, the plasma cladding is performed under the condition of introducing a protective gas; specifically, the protective gas includes an inert gas, such as argon, etc. In some embodiments of the present invention, the introduction flow rate of the protective gas is 15 to 20 L / min.

[0031] In some embodiments of the present invention, before plasma cladding, a step of drying the titanium nitride powder is also included. Specifically, the drying temperature may be 100 to 150°C, such as 120°C; the drying time may be 1 to 5 hours, such as 2 hours. More specifically, the drying step is as follows: drying the titanium nitride powder in a vacuum drying oven at a temperature of 120°C for 2 hours.

[0032] In some embodiments of the present invention, before plasma cladding, the titanium substrate is further polished and cleaned. Specifically, the sandpaper used for polishing may be SiC sandpaper; the mesh of the sandpaper may be 400-800 mesh; the cleaning agent may be anhydrous ethanol; the purity of anhydrous ethanol is ≥99%. More specifically, the polishing step is as follows: polishing the titanium substrate with 400 mesh and 800 mesh SiC sandpaper in sequence until the titanium substrate has a clear metallic luster and no defects visible to the naked eye; the cleaning step is as follows: cleaning the polished titanium substrate with anhydrous ethanol having a purity greater than 99%.

[0033] In some specific embodiments of the present invention, after the polishing and cleaning steps of the titanium substrate are completed, the titanium nitride coating is prepared by plasma cladding within 2 hours. In order to avoid the formation of excessive oxide layers on the surface of the titanium substrate, thereby affecting the bonding strength, the plasma cladding coating needs to be completed within 2 hours after polishing and cleaning.

[0034] The second aspect of the present invention provides a titanium material, comprising a titanium substrate and a titanium nitride coating disposed on the surface of the titanium substrate; the titanium nitride coating is prepared by the preparation method described in the first aspect of the present invention.

[0035] The titanium substrate described in the second aspect of the present invention is the titanium substrate described in the first aspect of the present invention.

[0036] In some embodiments of the present invention, the physical phase composition of the titanium nitride coating includes at least one of a titanium nitride phase, an α-Ti phase, or a β-Ti phase; in some specific embodiments of the present invention, the physical phase composition of the titanium nitride coating includes a titanium nitride phase and an α-Ti phase, or a titanium nitride phase, an α-Ti phase, and a β-Ti phase.

[0037] In some embodiments of the present invention, the metallographic structure of the titanium nitride coating includes at least one of equiaxed crystals, dendrites or martensite; in some specific embodiments of the present invention, the metallographic structure of the titanium nitride coating includes equiaxed crystals, dendrites and martensite.

[0038] In some embodiments of the present invention, the thickness of the titanium nitride coating is ≥1 mm; in some specific embodiments of the present invention, the thickness of the titanium nitride coating is ≥2 mm; in some more specific embodiments of the present invention, the thickness of the titanium nitride coating is 2-4 mm.

[0039] The method of the present invention can prepare a coating with a thickness exceeding 1 mm or even exceeding 2 mm, while methods such as physical vapor deposition (PVD) can usually only reach a level of several microns to hundreds of microns. The titanium nitride coating prepared by the present invention is more suitable for high-load and long-life working conditions, such as aerospace, precision machinery and high-end mold manufacturing.

[0040] In some embodiments of the present invention, the microhardness of the titanium nitride coating is ≥500 HV 0.1 In some specific embodiments of the present invention, the microhardness of the titanium nitride coating is 550HV 0.1 ~1124HV 0.1 .

[0041] A third aspect of the present invention provides a structural component, which comprises the titanium material according to the second aspect of the present invention.

[0042] The titanium nitride coating is prepared on the surface of a titanium substrate by the preparation method provided by the present invention, and the obtained titanium material can be used to prepare structural parts. Since the prepared coating can significantly improve the hardness of the titanium material surface, effectively reduce friction loss, and reduce the wear of the titanium material, the service life of the parts can be increased, and structural parts with good wear resistance can be obtained.

[0043] The fourth aspect of the present invention provides an application of the titanium material as described in the second aspect of the present invention, or the structural part as described in the third aspect of the present invention in the fields of aerospace, precision machinery or high-end equipment manufacturing.

[0044] The titanium material and structural parts provided by the present invention have good wear resistance and can meet the needs of aerospace, precision machinery, high-end mold manufacturing and other fields for high-performance wear-resistant coatings.

[0045] The beneficial effects of the present invention are as follows: the present invention uses a plasma cladding method under specific conditions to allow sufficient element diffusion between titanium nitride powder and the surface of the titanium substrate to form a dense coating without cracks, holes and excellent bonding performance. The method uses a single titanium nitride powder as a cladding material, avoiding the compatibility problems that may be caused by multi-component cladding materials, and ensuring the purity and performance of the coating. In addition, the titanium nitride coating prepared by the present invention has the characteristics of high hardness and low friction coefficient, which can effectively extend the service life of components in high friction environments. The prepared titanium materials and structural parts have a wide range of applications in the fields of aerospace, precision machinery or high-end equipment manufacturing.

[0046] Specifically, compared with the prior art, the present invention has the following advantages:

[0047] 1. From the perspective of crystallography, the present invention selects titanium nitride powder with good lattice matching with the titanium substrate as the coating raw material. For example, the face-centered cubic (FCC) structure of titanium nitride matches the hexagonal close-packed (HCP) structure of α titanium alloy to a certain extent, so that titanium nitride can better form a stable bond with the substrate during the cladding process. At the same time, titanium nitride itself has the characteristics of high hardness and low friction coefficient, which makes the coating have better wear resistance in a friction and wear environment.

[0048] 2. Compared with the metal ceramic coating prepared by traditional plasma spraying technology, which mainly relies on mechanical bonding and results in limited bonding strength, the present invention is based on plasma cladding technology with high energy density input, which makes the titanium nitride powder partially melt with the substrate surface during the cladding process and forms a metallurgical bonding interface through rapid solidification. This bonding method significantly improves the adhesion strength and anti-peeling ability of the coating, enabling it to maintain stable performance in complex service environments.

[0049] 3. Based on the high energy input of plasma cladding, titanium nitride powder can fully diffuse with the surface of titanium alloy to form a coating with an α-Ti / titanium nitride composite structure. This structure can not only utilize the high hardness and wear resistance of titanium nitride, but also use the moderate ductility of α-Ti to improve the overall toughness of the coating, avoid brittle fracture, and improve the comprehensive service performance.

[0050] 4. The present invention can prepare coatings with a thickness exceeding 1 mm or even exceeding 2 mm, which is far beyond the thickness range that can be achieved by traditional coating methods such as PVD. At the same time, it can form a dense microstructure with uniform organization, no voids, and no cracks, and can also effectively reduce the risk of crack propagation caused by stress concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 for Figure 1 1 and 2 are XRD patterns and electron microscope photographs of the TiN powder used in the examples.

[0052] Figure 2 XRD patterns of the titanium nitride coatings prepared in Examples 1 to 4.

[0053] Figure 3 It is an optical microscope image of the surface of the titanium nitride coating prepared in Examples 1 to 4.

[0054] Figure 4 It is the organization diagram of the surface of the titanium nitride coating prepared in Examples 1 to 4 after chemical etching.

[0055] Figure 5 It is the morphology picture of the cross section of the titanium nitride coating prepared in Examples 1 to 4.

[0056] Figure 6 This is a microstructure diagram of the cross section of the titanium nitride coating prepared in Example 3 after chemical etching.

[0057] Figure 7 It is a statistical chart of the thickness of the titanium nitride coating prepared in Examples 1 to 4.

[0058] Figure 8 The hardness distribution diagram of the cross section of the titanium nitride coating prepared in Examples 1 to 4.

[0059] Fig. 9It is a statistical chart of the average hardness of the entire coating of Examples 1 to 5 and the sample of Comparative Example 1.

[0060] Fig.10 This is a morphology diagram of the cross section of the titanium nitride coating prepared in Example 5. DETAILED DESCRIPTION

[0061] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0062] Example 1

[0063] A method for preparing a titanium nitride coating comprises the following steps:

[0064] (1) Titanium nitride powder with an average particle size of 72.29 μm (in atomic percentage, Ti 50.42%, N 48.62%, C 0.008%, O 0.054%, and the remainder is inevitable impurities) is weighed according to the powder mass required for the cladding coating and placed in a vacuum drying oven for drying to remove residual moisture on the powder surface and ensure the fluidity of the powder during the cladding process to obtain a uniform coating. The vacuum drying temperature is 100°C, the drying time is 120 min, and the vacuum drying degree is 0.05 MPa to obtain dried titanium nitride powder;

[0065] (2) The Ti6Al4V substrate was cut into a rectangular titanium plate of 100 mm × 20 mm × 10 mm by an electric spark wire cutting machine, and polished with 400-mesh and 800-mesh SiC sandpapers in sequence until the substrate had a clear metallic luster and no defects visible to the naked eye. After polishing, it was cleaned with anhydrous ethanol with a purity of >99.99% to obtain a pretreated Ti6Al4V substrate;

[0066] (3) The titanium nitride powder dried in step (1) is placed in the powder feeding barrel of plasma cladding, and the nozzle of the plasma cladding device is adjusted to be 10.0 mm away from the surface of the titanium alloy Ti6Al4V substrate in step (2). Then, the titanium nitride powder obtained in step (1) is clad on the surface of the Ti6Al4V substrate pretreated in step (2) by operating the plasma cladding device in a synchronous powder feeding manner. The entire cladding process is carried out in an argon protective gas with a purity greater than 99.99% at 18 L / min. The ion gas for plasma cladding uses pure argon with a purity greater than 99.99%, the ion gas flow rate is 1.0 L / min, the plasma cladding current is 100 A, the plasma cladding scanning rate is 1.5 mm / s, the powder feeding rate is 2.4 g / min, and the powder feeding gas flow rate is 4 L / min. After synchronous powder feeding of plasma cladding, an α-Ti / TiN dual-phase titanium nitride coating is obtained on the substrate.

[0067] Example 2

[0068] A method for preparing a titanium nitride coating, which differs from Example 1 in that the plasma cladding current in step (3) of this example is 110A; the other steps and preparation conditions are the same as those in Example 1.

[0069] Example 3

[0070] A method for preparing a titanium nitride coating, which differs from Example 1 in that the plasma cladding current in step (3) of this example is 120A; the other steps and preparation conditions are the same as those in Example 1.

[0071] Example 4

[0072] A method for preparing a titanium nitride coating, which differs from Example 1 in that the plasma cladding current in step (3) of this example is 130A; the other steps and preparation conditions are the same as those in Example 1.

[0073] Example 5

[0074] A method for preparing a titanium nitride coating, which differs from Example 3 in that the powder feeding rate in step (3) of this example is 4.8 g / min; the other steps and preparation conditions are the same as those of Example 3.

[0075] Comparative Example 1

[0076] A Ti6Al4V substrate (the same as the Ti6Al4V substrate in Example 1) is provided without using plasma cladding to prepare a titanium nitride coating on the surface of the substrate.

[0077] Performance Testing

[0078] 1. X-ray diffraction (XRD) test

[0079] (1) TiN powder: The TiN powder used in the embodiment of the present invention was subjected to phase detection by a Bruker D8 X-ray diffractometer, wherein the abscissa represents the diffraction angle 2θ (°) and the ordinate represents the diffraction intensity. The surface morphology and particle size range of the TiN powder were observed by a PhenomXL high-throughput desktop fully automatic scanning electron microscope.

[0080] Figure 1 The following are XRD patterns and electron microscope photos of the TiN powder used in the examples, where (a) is the XRD pattern and (b) is the electron microscope photo. Figure 1 It can be seen that the TiN powder fed in presents a single TiN crystal structure without other impurity peaks, and the particle size range of the TiN powder fed in is 53-105 μm.

[0081] (2) Coating: The titanium nitride coating sample prepared in the embodiment was subjected to electric spark wire cutting, and the coating surface was polished with 400 mesh, 800 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to obtain an X-ray phase detection sample. Then, the coating prepared in the embodiment of the present invention was subjected to phase detection by a Bruker D8 X-ray diffractometer. The results are as follows: Figure 2 As shown, the abscissa represents the diffraction angle 2θ (°), and the ordinate represents the diffraction intensity.

[0082] Figure 2 The XRD patterns of the titanium nitride coatings prepared in Examples 1 to 4 are shown in Figure 1, (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Figure 2 It can be seen that the TiN coatings prepared in Examples 1 to 4 of the present invention are mainly composed of hexagonal α-Ti and TiN phases. At the same time, in the sample of Example 4, since the surface of the titanium alloy substrate participates too much in the formation of the coating, a small amount of β-Ti diffraction peaks also appear in the coating.

[0083] 2. Bonding strength test

[0084] The tensile bonding strength of the samples of the embodiment was tested by a universal mechanical testing machine in accordance with the Chinese national standard GB / T8642-2002. The testing method is as follows: DSY-095 film (ultimate strength of 65 MPa) was used to bond the titanium nitride coating and the substrate side respectively, and the tensile bonding strength of the coating was tested by a universal mechanical testing machine.

[0085] During the test, when the film was torn, the titanium nitride coating and the substrate were still not separated, so it can be judged that the bonding strength between the titanium nitride coating and the substrate in Examples 1 to 5 of the present invention is greater than 65MPa, and has good bonding performance, so that the titanium nitride coating can play a good protective role on the substrate. The bonding strength of the metal ceramic coating prepared by traditional plasma spraying technology is less than the ultimate strength of the film 65MPa, which shows that the titanium nitride coating provided by Examples 1 to 5 of the present invention is superior to the metal ceramic coating prepared by traditional processes.

[0086] 3. Observation of morphology after surface grinding and polishing

[0087] The titanium nitride coating prepared in the embodiment was segmented by electric spark wire cutting to obtain a square sample of 10 mm×10 mm×10 mm, and the coating surface was exposed by cold mounting material, and then the surface was polished with sandpaper of 400 mesh, 800 mesh, 1200 mesh, 1500 mesh and 2000 mesh in sequence until the scratches were uniform, and then the surface was polished with diamond polishing liquid of 9 microns, 1 microns and 0.04 microns in sequence until there were basically no scratches. Then the surface morphology of the coating was observed by Leica DM2700 metallographic microscope.

[0088] Figure 3 The optical microscope images of the titanium nitride coating surfaces prepared in Examples 1 to 4, wherein (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. It can be seen that the coating surfaces of Examples 1 to 4 are uniform and dense, without cracks and holes.

[0089] 4. Surface metallographic structure observation

[0090] The metallographic structure of the titanium nitride coating sample prepared in the embodiment was observed by chemical etching (the chemical etching agent is HF:HNO 3 :H 2 After etching for about 15 seconds with Keller reagent (O=3:5:92 (volume ratio)), the metallographic microstructure was observed using a Leica (Leica DM2700) metallographic microscope.

[0091] Figure 4 The following are the microstructures of the titanium nitride coating surfaces prepared in Examples 1 to 4 after chemical etching, wherein (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. It can be seen that the coating surfaces in Examples 1 and 2 are mainly composed of unmelted TiN particles and equiaxed crystals; the grain morphology in Example 3 is mainly equiaxed crystals with a small amount of dendrites; the surface grain morphology in Example 4 is mainly dendrites with a small amount of equiaxed crystals.

[0092] 5. Observation of the morphology after cross-section grinding and polishing

[0093] The titanium nitride coating prepared in the embodiment was segmented by electric spark wire cutting to obtain a square sample of 10 mm×10 mm×10 mm, and the cross section of the coating was exposed by cold mounting material, and then the cross section was polished with sandpaper of 400 mesh, 800 mesh, 1200 mesh, 1500 mesh and 2000 mesh in sequence until the scratches were uniform, and then the surface was polished with diamond polishing liquid of 9 microns, 1 microns and 0.04 microns in sequence until there were basically no scratches. Then the cross-sectional morphology of the coating was observed by a Leica (Leica DM2700) metallographic microscope.

[0094] Figure 5 The morphology diagrams of the cross sections of the titanium nitride coatings prepared in Examples 1 to 4 are shown in Figures 1 to 4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. It can be seen that the cross section of the coating is uniform and dense, without cracks, and the interface exhibits good metallurgical bonding characteristics. At the same time, it can be seen that from Example 1 to Example 4, the unmelted particles gradually decrease, which is mainly because the increase in cladding current will change the energy input. By controlling the cladding current, the distribution form of the titanium nitride powder fed in the coating can be effectively controlled.

[0095] 6. Cross-section metallographic structure observation

[0096] The metallographic structure of the titanium nitride coating sample cross section prepared in the embodiment is observed by chemical etching (chemical etching agent is HF:HNO 3 =3:5:92 (volume ratio) Keller reagent) after etching for about 15s, the metallographic microstructure was observed under a Leica (Leica DM2700) metallographic microscope.

[0097] Figure 6 This is the microstructure diagram of the titanium nitride coating cross section prepared in Example 3 after chemical etching, where (a) is the cross section of the upper part of the coating, (b) is the cross section of the middle part of the coating, and (c) is the cross section of the coating and substrate bonding area. As can be seen from the figure, the grain morphology of the coating surface in Example 3 is mainly equiaxed crystals with a small amount of dendrites; the central area develops a petal-shaped eutectic structure due to the local solute redistribution caused by convection; the bonding area between the coating and the substrate is mainly a martensite area. The overall microstructure of the coating is dense, uniform, and the interface bonding is good.

[0098] 7. Coating thickness measurement

[0099] The thickness of the titanium nitride coating sample prepared in the example was counted by a Leica DM2700 metallographic microscope.

[0100] Figure 7It is a statistical chart of the thickness of the titanium nitride coating prepared in Examples 1 to 4. The average thickness of the samples in Examples 1 to 4 are 2.46 mm, 2.71 mm, 3.38 mm, and 3.95 mm, respectively. It can be seen that the coating thickness increases from Example 1 to Example 4, which is mainly because the increase in cladding current will change the energy input, and the coating thickness can be effectively controlled by controlling the cladding current.

[0101] 8. Coating hardness measurement

[0102] According to the national standard GB / T4340.1-2024, the hardness of the titanium nitride coating prepared in the embodiment was measured by a Vickers hardness tester (HVS-1000) of Guangzhou Weiyi Metallographic Testing Instrument Co., Ltd. The Vickers hardness tester has a dwell time of 10s, a test force of 0.1kg, and a spacing of 100μm between adjacent test points from the coating surface to the bonding area. The test results are as follows: Figure 8 shown.

[0103] Figure 8 The hardness distribution diagram of the cross section of the titanium nitride coating prepared in Examples 1 to 4, wherein the zero point of the horizontal axis represents the position of the bonding area between the coating and the substrate, and the gradually increasing value represents the gradual approach from the bonding area to the coating surface. As can be seen from the figure, in Example 1, due to the presence of a large number of unmelted TiN particles in the coating, the hardness distribution of the coating surface is all above 1000 HV. 0.1 In Example 2, as the cladding current energy density input increases, the number of unmelted particles in the coating decreases, and the hardness test will inevitably test the unmelted particles, so the hardness is between 500-2000HV 0.1 As the cladding current increases further, there are basically no unmelted particles in the coating, and the hardness in Examples 3 and 4 fluctuates within a small range.

[0104] Fig. 9 The average hardness statistics of the coatings of Examples 1 to 5 and the sample of Comparative Example 1 are shown in the figure. As can be seen from the figure, the average hardness of the cladding layer gradually decreases with the increase of the cladding current. In Examples 1 and 2 with lower cladding currents, due to the presence of a large number of unmelted particles, the hardness fluctuates in a large range, with a large error range, and the fluctuation range is 582.45-1666.37 HV respectively. 0.1 and 455.27-1321.07HV 0.1 As the current increases further, the average hardness value of Example 3 is 632.12 HV 0.1 , compared with 344.93HV of the substrate in Comparative Example 1 0.1 It has been improved by 83.26%, and the error range fluctuates slightly to 581.81-682.43HV 0.1When the current is further increased, in Example 4, the substrate participates too much in the formation of the coating, so compared with Example 3, the hardness of the coating in Example 4 decreases by 72.23 HV. 0.1 At the same time, it can be seen that when other conditions remain unchanged, increasing the powder feeding amount will increase the hardness of the coating. Compared with Example 3, the average hardness of Example 5 is increased from 632.12 HV 0.1 Increased to 1415.81HV 0.1 , but its error range is also large, with a fluctuation range of 799.43-2032.19HV 0.1 .

[0105] Fig.10 This is a morphology diagram of the cross section of the titanium nitride coating prepared in Example 5. It can be seen that when other cladding conditions remain unchanged, a higher powder feeding rate (4.8 g / min) will lead to uneven distribution of TiN particles in the coating, and too high a TiN phase content will produce more cracks during the friction process, thereby affecting its corrosion resistance under service conditions. Therefore, the present invention needs to obtain a coating with better organizational structure and performance for a specific specific process.

[0106] Compared with the simple Ti6Al4V substrate in Comparative Example 1, in the embodiment of the present invention, a plasma cladding technology is used to use a high-energy plasma beam as a heat source, and TiN powder is simultaneously fed and melted with the substrate surface to prepare a composite coating of α-Ti and TiN crystal structure. The coating has a dense structure, no holes and cracks, which not only significantly improves the hardness of the titanium alloy surface, but also further enhances its wear resistance. The high hardness of the TiN phase effectively improves the anti-friction performance of the coating, and the moderate ductility of α-Ti can help optimize the overall toughness of the coating and reduce the risk of failure caused by brittle fracture. In addition, the coating thickness prepared by the present invention can reach more than 1 mm, far exceeding the coating thickness limit of the traditional deposition method, ensuring more lasting protection under extreme working conditions such as high load and high friction. Therefore, the method and the coating prepared by the method can be widely used in aerospace, precision manufacturing, high-end molds and biomedical equipment, etc., which have high requirements for wear resistance and coating thickness, and meet the application requirements in harsh service environments.

[0107] In summary, the present invention uses a plasma cladding method under specific conditions to allow sufficient element diffusion between titanium nitride powder and the surface of the titanium substrate to form a dense coating without cracks, holes and excellent bonding performance. This method uses a single titanium nitride powder as a cladding material, avoiding the compatibility problems that may be caused by multi-component cladding materials, and ensuring the purity and performance of the coating. In addition, the titanium nitride coating prepared by the present invention has the characteristics of high hardness and low friction coefficient, which can effectively extend the service life of components in high friction environments. The prepared titanium materials and structural parts have a wide range of applications in the fields of aerospace, precision machinery or high-end equipment manufacturing.

Claims

1. A method for preparing a titanium nitride coating, characterized in that: The following steps are involved: Titanium nitride powder is subjected to plasma cladding to prepare a titanium nitride coating on the surface of a titanium substrate; the current of the plasma cladding is 80 to 160A.

2. The preparation method according to claim 1, characterized in that: The oxygen content of the titanium nitride powder is ≤500ppm; And / or, the purity of the titanium nitride powder is ≥99.9%; And / or, the average particle size of the titanium nitride powder is 50 to 105 μm.

3. The preparation method according to claim 1, characterized in that: The titanium substrate includes a pure titanium substrate or a titanium alloy substrate.

4. The preparation method according to claim 1, characterized in that: The plasma cladding adopts a synchronous powder feeding method.

5. The preparation method according to claim 4, characterized in that: The synchronous powder feeding rate is 1.0-5.0 g / min; And / or, the powder feeding gas flow rate of the synchronous powder feeding is 3.0-6.0 L / min.

6. The preparation method according to claim 1, characterized in that: The ion gas for plasma cladding is selected from pure argon; The purity of the pure argon gas is ≥99.99%; And / or, the ion gas flow rate of the plasma cladding is 0.5 to 3.0 L / min; And / or, the cladding rate of the plasma cladding is 1.0 to 3.0 mm / s.

7. A titanium material, characterized in that: The titanium material comprises a titanium substrate and a titanium nitride coating disposed on the surface of the titanium substrate; the titanium nitride coating is prepared by a preparation method according to any one of claims 1 to 6.

8. The titanium material according to claim 7, characterized in that: The phase composition of the titanium nitride coating includes at least one of a titanium nitride phase, an α-Ti phase or a β-Ti phase; And / or, the metallographic structure of the titanium nitride coating includes at least one of equiaxed crystals, dendrites or martensite; And / or, the thickness of the titanium nitride coating is ≥1 mm.

9. A structural member, characterized in that: The structural member comprises the titanium material according to claim 7 or 8.

10. Use of the titanium material according to claim 7 or 8, or the structural component according to claim 9 in the fields of aerospace, precision machinery or high-end equipment manufacturing.

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