A method for producing a titanium nitride coating and the use thereof

Abstract

The application discloses a preparation method of a titanium nitride coating and application of the titanium nitride coating. The preparation method of the titanium nitride coating comprises the following steps: adopting a coaxial magnetron plasma acceleration method, taking industrial pure titanium as an acceleration electrode material, performing pulse discharge, and generating titanium plasma of the acceleration electrode material; under the action of electromagnetic force, the titanium plasma forms a titanium plasma jet at an outlet of the acceleration electrode; the titanium plasma jet reacts with nitrogen-containing gas to deposit and form the titanium nitride coating on a substrate surface. The coaxial magnetron plasma acceleration method is adopted, industrial pure titanium is used as an acceleration electrode, and nitrogen-containing gas is used as a specific material input source to form the titanium plasma jet. The high-speed and high-reactivity titanium plasma jet is beneficial to enhancing the impact, spreading, diffusion and reaction process of the deposition particles on the substrate surface, promoting the densification of the coating and the stable combination between the coating and the substrate, and the titanium nitride coating with high bonding strength and good wear resistance can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, and particularly relates to a method for preparing titanium nitride coatings and their applications. Background Technology

[0002] Titanium materials, especially titanium alloys, are widely used in aerospace, precision machinery, biomedicine, and high-end equipment manufacturing due to their low density, high specific strength, good corrosion resistance, and fatigue resistance. However, titanium alloys have relatively low surface hardness and insufficient wear resistance, making them prone to wear, seizing, and surface damage under high-load friction, sliding contact, and complex service environments. This limits their further application in dynamically moving parts and long-life wear-resistant structural components. Therefore, improving the surface hardness, wear resistance, and interfacial bonding stability of titanium alloys is of great significance.

[0003] Preparing titanium nitride coatings on titanium alloy surfaces is an effective method to improve their surface performance. Titanium nitride possesses high hardness, low coefficient of friction, good chemical stability, and wear resistance, making it suitable as a wear-resistant protective coating for titanium alloy surfaces. Currently, titanium nitride and related cermet coatings are typically prepared using methods such as physical vapor deposition (PVD), laser cladding, plasma cladding, plasma spraying, or high-speed oxy-fuel spraying. However, PVD coatings are usually limited in thickness and have low deposition efficiency, making it difficult to meet the demand for thick coatings under high load conditions. Laser cladding, plasma cladding, and thermal spraying processes typically rely on pre-formed powders, which can easily lead to problems such as incompletely melted particles, pores, cracks, component segregation, or uneven distribution of hard phases. Traditional spray coatings are mostly mechanically bonded to the substrate, and oxide films, pores, and unbonded areas may exist at the interface, affecting the coating's bonding strength and long-term service stability. Summary of the Invention

[0004] To overcome at least one of the problems existing in the prior art, one of the objectives of this invention is to provide a method for preparing a titanium nitride coating. This method directly utilizes a titanium source to react in situ with a nitrogen-containing atmosphere during the deposition process, and enhances the impact, spreading, diffusion and reaction processes between the deposited particles and the substrate surface through high-speed, high-kinetic-energy deposition, thereby directly generating a titanium nitride coating on the substrate surface. This reduces the dependence on pre-prepared titanium nitride powder or composite metal ceramic powder, simplifies the preparation process, and improves the compositional uniformity, microstructure density and interfacial bonding quality of the coating.

[0005] The second objective of this invention is to provide a titanium nitride coating prepared by the above-mentioned method.

[0006] The third objective of this invention is to provide a structural component.

[0007] The fourth objective of this invention is to provide a method for preparing the above-mentioned titanium nitride coating, and the application of the titanium nitride coating or structural components.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a method for preparing a titanium nitride coating, comprising the following steps: using a coaxial magnetron plasma acceleration method, with industrially pure titanium as the accelerating electrode material, pulse discharge is performed, and the accelerating electrode material generates titanium plasma; the titanium plasma forms a titanium plasma jet from the accelerating electrode outlet under the action of electromagnetic force; the titanium plasma jet reacts with a nitrogen-containing gas to deposit the titanium nitride coating on the surface of a substrate.

[0009] This invention employs a coaxial magnetron plasma acceleration method, which generates titanium plasma through pulsed discharge using an accelerating electrode material. Under electromagnetic force, the plasma is directionally accelerated to form a titanium plasma jet, characterized by high particle velocity, concentrated energy input, and strong reactivity. Using industrially pure titanium as the accelerating electrode material, this invention generates and transports the titanium plasma jet in a nitrogen-containing gas. During deposition, the titanium source directly reacts with the nitrogen-containing gas in situ. High-speed, high-kinetic-energy deposited particles enhance the impact, spreading, diffusion, and reaction processes with the substrate surface, directly generating a titanium nitride coating. Compared to existing coating preparation methods that rely on pre-prepared titanium nitride powder or composite metal-ceramic powder, this invention changes the coating material input source from externally added titanium nitride powder to an industrially pure titanium accelerating electrode and nitrogen-containing gas. This effectively reduces problems such as particle agglomeration, component segregation, incompletely melted particles, and uneven distribution during powder preparation, transportation, and melting. It simplifies the preparation process, improves the coating's component uniformity, microstructure density, and interfacial bonding quality, thereby producing a titanium nitride coating with high bonding strength and good wear resistance.

[0010] In some embodiments of the present invention, the coaxial magnetron plasma acceleration method can be based on a coaxial magnetron plasma accelerator.

[0011] In some embodiments of the present invention, the titanium plasma jet reacts in situ with nitrogen-containing gas during the transport and / or deposition processes.

[0012] In some embodiments of the present invention, the nitrogen-containing gas includes nitrogen.

[0013] In some embodiments of the present invention, the pressure of the nitrogen gas is 0.04~0.15 MPa; for example, it can be any value or a range between any two of 0.04 MPa, 0.06 MPa, 0.08 MPa, 0.1 MPa, 0.12 MPa or 0.15 MPa; in some specific embodiments of the present invention, the pressure of the nitrogen gas is 0.06~0.12 MPa; in some more specific embodiments of the present invention, the pressure of the nitrogen gas is 0.08~0.12 MPa.

[0014] The present invention utilizes the aforementioned nitrogen pressure range, which facilitates the synergistic matching between titanium plasma transport and the titanium-nitrogen reaction, thereby obtaining a titanium nitride coating with dense structure, uniform composition, good bonding, and high hardness and wear resistance. Specifically, by controlling the nitrogen pressure, the transport state of titanium plasma in a nitrogen-containing atmosphere and the degree of titanium-nitrogen reaction can be adjusted. Using a suitable nitrogen pressure ensures that the titanium plasma and nitrogen have an appropriate degree of reaction, fully generating titanium nitride, and reducing the collisions, scattering, and thermal effects experienced by the titanium plasma during transport, resulting in a coating with good continuous deposition and uniform structure.

[0015] In some embodiments of the present invention, the pulse discharge is powered by a capacitor energy storage unit.

[0016] In some embodiments of the present invention, the charging voltage of the capacitor energy storage unit is 3~4kV; for example, it can be any value or a range between 3kV, 3.2kV, 3.4kV, 3.5kV, 3.6kV, 3.8kV or 4kV.

[0017] In some embodiments of the present invention, the capacitance value of the capacitor energy storage unit is 7.2~20mF; for example, it can be any value or a range between 7.2mF, 8mF, 10mF, 12mF, 15mF, 17mF or 20mF.

[0018] This invention, by controlling the charging voltage and capacitance value of the capacitor energy storage unit, can provide a stable energy input for the generation and axial acceleration of titanium plasma, which is beneficial for promoting the formation of high-speed titanium plasma jets and achieving coating deposition.

[0019] In some embodiments of the present invention, the industrial pure titanium undergoes at least one of ablation, ionization or plasmaification during pulsed discharge to form the titanium plasma.

[0020] In some embodiments of the present invention, the titanium plasma is formed by Z-pinch and axial acceleration in the coaxial magnetron plasma acceleration method to form the titanium plasma jet.

[0021] In some embodiments of the present invention, the initial velocity of the titanium plasma jet at the outlet of the accelerating electrode is ≥2 km / s; specifically, it can be 2 to 4 km / s, for example, any value of 2 km / s, 2.5 km / s, 3 km / s, 3.5 km / s or 4 km / s or any value between two of them.

[0022] In some embodiments of the present invention, the industrial pure titanium is used as the cylindrical accelerating electrode material of the coaxial magnetron plasma accelerator.

[0023] In some embodiments of the present invention, the purity of the industrial pure titanium is ≥99%; specifically, it can be 99~99.9%, for example, it can be any value or a range between any two of 99%, 99.2%, 99.4%, 99.6%, 99.8% or 99.9%.

[0024] In some embodiments of the present invention, the industrial pure titanium comprises TA1, TA2, or a combination thereof.

[0025] In some embodiments of the present invention, a step of preheating the substrate is further included before performing the pulse discharge.

[0026] Preheating the substrate can reduce the temperature gradient and instantaneous thermal shock on the substrate surface during high-speed titanium plasma deposition, promoting the spread, diffusion and reaction of the deposit on the substrate surface, which is beneficial to improving the density of the coating and the bonding performance between the coating and the substrate.

[0027] In some embodiments of the present invention, the preheating temperature is 200~300℃; for example, it can be any value or a range between any two of 200℃, 220℃, 240℃, 250℃, 260℃, 280℃ or 300℃; in some specific embodiments of the present invention, the preheating temperature is 240~260℃.

[0028] In some embodiments of the present invention, the substrate is preheated after the nitrogen pressure stabilizes at a preset nitrogen pressure.

[0029] In some embodiments of the present invention, a pretreatment step of the substrate is further included before pulse discharge.

[0030] In some embodiments of the present invention, the pretreatment includes at least one of grinding, polishing, cleaning, drying, degreasing, or removing oxide layer.

[0031] In some embodiments of the present invention, the cleaning agent includes at least one of anhydrous ethanol, acetone or deionized water.

[0032] In some embodiments of the present invention, the titanium plasma jet reacts with nitrogen-containing gas in a reaction chamber.

[0033] In some embodiments of the present invention, the reaction chamber is further subjected to an atmosphere replacement step before pulse discharge.

[0034] In some embodiments of the present invention, the atmosphere replacement includes the steps of evacuating the reaction chamber, filling it with high-purity nitrogen, and evacuating it again.

[0035] In some embodiments of the present invention, the atmosphere replacement includes at least one evacuation and nitrogen purging cycle. By evacuating and purging, the content of impurities such as residual air, oxygen, and water vapor in the reaction chamber can be reduced, thereby minimizing the impact of impurity gases on the titanium plasma nitriding reaction and coating composition, which is beneficial for improving the phase composition stability and microstructure uniformity of the titanium nitride coating.

[0036] In some embodiments of the present invention, after atmosphere replacement, the nitrogen pressure in the reaction chamber is stabilized to a preset nitrogen pressure before pulse discharge is performed.

[0037] In some embodiments of the present invention, the distance from the accelerating electrode outlet to the surface of the substrate is 200-400 mm; for example, it can be any value of 200 mm, 250 mm, 300 mm, 350 mm or 400 mm or a range between any two; in some specific embodiments of the present invention, the distance from the accelerating electrode outlet to the surface of the substrate is 250-350 mm.

[0038] By adjusting the distance from the accelerating electrode outlet to the substrate surface, the velocity, temperature, diffusion range, and reaction degree of the titanium plasma reaching the substrate surface can be controlled. Using an appropriate distance can reduce the instantaneous thermal shock to the substrate surface, avoiding excessive pitting on the coating surface; and it can reduce energy attenuation and divergence of the titanium plasma jet during transport, ensuring good deposition continuity in the coating. Therefore, using the above-mentioned distance range is beneficial for obtaining titanium nitride coatings with good deposition continuity and more uniform microstructure.

[0039] In some embodiments of the present invention, the substrate includes a titanium substrate or a titanium alloy substrate; in some specific embodiments of the present invention, the substrate is a Ti6Al4V (TC4) titanium alloy substrate.

[0040] A second aspect of the present invention provides a titanium nitride coating prepared by the preparation method described in the first aspect of the present invention.

[0041] In some embodiments of the present invention, the phase composition of the titanium nitride coating includes at least one of TiN phase, Ti(N) phase or α-Ti phase.

[0042] In some embodiments of the present invention, the Ti and N elements in the titanium nitride coating are continuously or gradient distributed along the coating cross section.

[0043] In some embodiments of the present invention, the titanium nitride coating has a continuous and dense structure.

[0044] In some embodiments of the present invention, the titanium nitride coating includes at least one of a TiN enrichment region, a Ti(N) transition region, or a titanium nitride reaction layer.

[0045] In some embodiments of the present invention, the titanium nitride coating forms a metallurgical bond, diffusion bond, or reactive bond with the substrate.

[0046] In some embodiments of the present invention, the tensile bond strength between the titanium nitride coating and the substrate is greater than or equal to 65 MPa.

[0047] In some embodiments of the present invention, the microhardness of the titanium nitride coating is higher than that of the substrate.

[0048] In some embodiments of the present invention, the average microhardness HV0.025 of the titanium nitride coating is greater than or equal to 500; specifically, it can be 500 to 800, for example, it can be any value or a range between any two of 500, 550, 600, 650, 700, 750 or 800, such as 500 to 750, 550 to 750, 650 to 750, etc.

[0049] A third aspect of the present invention provides a structural component comprising a substrate and a titanium nitride coating disposed on the surface of the substrate; the titanium nitride coating is prepared by the preparation method described in the first aspect of the present invention, or the titanium nitride coating is the titanium nitride coating described in the second aspect of the present invention.

[0050] The fourth aspect of the present invention provides a method for preparing a titanium nitride coating as described in the first aspect of the present invention, or a titanium nitride coating as described in the second aspect of the present invention, or a structural component as described in the third aspect of the present invention, in the fields of aerospace, precision machinery, mold manufacturing, energy equipment, marine equipment, or biomedical devices.

[0051] The titanium nitride coating preparation method, titanium nitride coating and structural components provided by this invention have wide applications in high-end equipment manufacturing fields such as aerospace, precision machinery, mold manufacturing, energy equipment, marine equipment or biomedical devices.

[0052] The beneficial effects of this invention are: This invention employs a coaxial magnetron plasma acceleration method, using industrial pure titanium accelerating electrodes and nitrogen-containing gas as specific material input sources. Through pulsed discharge, the accelerating electrode material generates titanium plasma, which is then directionally accelerated under electromagnetic force to form a titanium plasma jet. This high-speed, highly reactive titanium plasma jet enhances the impact, spreading, diffusion, and reaction processes between deposited particles and the substrate surface, promoting coating densification and stable bonding between the coating and the substrate. This invention effectively solves problems such as particle agglomeration, component segregation, incompletely melted particles, and uneven distribution caused by the addition of pre-formed titanium nitride powder, resulting in a titanium nitride coating with high bonding strength and good wear resistance. Attached Figure Description

[0053] Figure 1 The initial velocity statistics of titanium plasma jets at the exit of the coaxial magnetron plasma accelerating electrode under different N2 pressure conditions in Examples 1-4 are presented.

[0054] Figure 2 This is a high-speed photograph of the titanium plasma jet at different times under a pressure of 0.10 MPa N2 in Example 3.

[0055] Figure 3 The images show the XRD patterns of the titanium nitride coatings prepared in Examples 1-4.

[0056] Figure 4 This is a morphological image of the cross-section of the titanium nitride coating prepared in Example 3.

[0057] Figure 5 The image shows the morphology of the cross-section of the coating prepared in Comparative Example 2.

[0058] Figure 6 This is a microstructure diagram of the cross-section of the titanium nitride coating prepared in Example 3 after chemical etching.

[0059] Figure 7 This is a distribution diagram of Ti and N elements in the central region of the titanium nitride coating prepared in Example 3.

[0060] Figure 8 The graph shows the average microhardness of the titanium nitride coatings prepared in Examples 1-4 and Comparative Example 1. Detailed Implementation

[0061] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0062] Example 1 A method for preparing a titanium nitride coating, the specific steps of which are as follows: (1) Substrate pretreatment: The TC4 titanium alloy substrate was cut into rectangular samples using an electrical discharge wire cutter. The surface of the TC4 titanium alloy substrate was then ground stepwise using a handheld vibrating sander. The SiC sandpaper used was 120 mesh, 240 mesh, 360 mesh and 600 mesh respectively, until the substrate surface was smooth and free of obvious defects. After grinding, the substrate surface was cleaned with anhydrous ethanol to remove surface dust and organic contaminants, and then dried with dry gas to obtain the pretreated TC4 titanium alloy substrate.

[0063] (2) Electrode pretreatment: TA2 industrial pure titanium was used as the cylindrical accelerating electrode material for the coaxial magnetron plasma accelerator. Before assembly, the TA2 industrial pure titanium cylindrical accelerating electrode was cleaned in an ultrasonic cleaner containing anhydrous ethanol for 2 minutes to remove residual dust and contaminants from the electrode surface; after cleaning, it was dried with dry gas and then assembled into the coaxial magnetron plasma accelerator system.

[0064] (3) Nitrogen purging and substrate preheating of the reaction chamber: The pretreated TC4 titanium alloy substrate was placed in the deposition area of ​​the coaxial magnetron plasma accelerator, and the distance from the outlet of the coaxial magnetron plasma accelerator electrode to the surface of the TC4 titanium alloy substrate was adjusted to 300 mm. The reaction chamber was then sealed, and a vacuum pump was used to evacuate the reaction chamber to achieve a rough vacuum. High-purity nitrogen was then introduced into the reaction chamber to restore the pressure to near atmospheric pressure. The vacuum pump was used again to evacuate the reaction chamber to further replace the residual air. After the evacuation-nitrogen purging cycle, high-purity nitrogen was continued to be introduced into the reaction chamber, and the nitrogen pressure in the reaction chamber was stabilized at 0.06 MPa. After the nitrogen pressure in the reaction chamber stabilized, the TC4 titanium alloy substrate was preheated to 250°C, and then pulsed discharge deposition was performed.

[0065] (4) Preparation of titanium nitride coating: The capacitor energy storage unit is charged to the target voltage of 3.5kV via a fast charging system, and the capacitance of the capacitor energy storage unit is 14.4mF. Then, discharge is triggered according to the preset pulse timing sequence, so that the capacitor bank releases energy and forms a high current pulse in a short time. During the discharge process, the inner surface of the TA2 industrial pure titanium cylindrical accelerating electrode undergoes electro-erosion, ablation, evaporation, ionization and / or plasmaification, generating a high-speed titanium plasma jet. After being ejected from the TA2 industrial pure titanium cylindrical accelerating electrode, the high-speed titanium plasma jet enters the nitrogen-containing reaction chamber and reacts in situ with nitrogen during the transport process, deposition process and / or the early stage of deposition to form Ti-N components. Subsequently, the high-speed titanium plasma jet impacts and acts on the surface of the TC4 titanium alloy substrate, causing local instantaneous thermal effects or melting on the substrate surface, and forming a bond with the deposit during the rapid cooling process, finally preparing a titanium nitride coating on the surface of the TC4 titanium alloy substrate.

[0066] Example 2 A method for preparing a titanium nitride coating differs from Example 1 in that the nitrogen pressure in the reaction chamber in step (3) of this example is stabilized at 0.08 MPa; other conditions are the same as in Example 1.

[0067] Example 3 A method for preparing a titanium nitride coating differs from Example 1 in that the nitrogen pressure in the reaction chamber in step (3) of this example is stabilized at 0.10 MPa; other conditions are the same as in Example 1.

[0068] In this embodiment, when the nitrogen pressure is 0.10 MPa, the transport process of titanium plasma in the nitrogen-containing atmosphere and the in-situ reaction process of titanium and nitrogen can be better matched, which is beneficial to forming a titanium nitride coating with a denser structure, more uniform composition and higher titanium nitride phase content on the surface of TC4 titanium alloy substrate.

[0069] Example 4 A method for preparing a titanium nitride coating differs from Example 1 in that the nitrogen pressure in the reaction chamber in step (3) of this example is stabilized at 0.12 MPa; other conditions are the same as in Example 1.

[0070] Comparative Example 1 A TC4 titanium alloy substrate is identical to the pretreated TC4 titanium alloy substrate in Example 1. This comparative example only underwent cutting, grinding, cleaning, and drying; a titanium nitride coating was not prepared on its surface using a coaxial magnetron plasma accelerator.

[0071] Comparative Example 2 A method for preparing a titanium nitride coating using externally added titanium nitride powder, the specific steps of which are as follows: Using the method of step (1) in Example 1, a pretreated TC4 titanium alloy substrate was obtained; then, titanium nitride powder was used as the coating material, and a titanium nitride coating was prepared on the surface of the pretreated TC4 titanium alloy substrate by plasma cladding and simultaneous feeding of titanium nitride powder.

[0072] Performance testing 1. Combined strength test The tensile bond strength of the sample specimens was tested using a universal testing machine according to standard GB / T 8642-2002. The test method is as follows: DSY-095 film was used to bond the titanium nitride coating side and the substrate side respectively. The ultimate tensile strength of DSY-095 film is 65 MPa. Subsequently, the tensile bond strength between the coating and the substrate was tested using a universal testing machine.

[0073] During the test, when the film tore, the titanium nitride coating did not separate from the substrate. Therefore, it can be determined that the bonding strength between the titanium nitride coatings prepared in Examples 1-4 of this invention and the substrate is greater than 65 MPa. This result indicates that the titanium nitride coating prepared by this invention has good bonding performance with the substrate and can effectively protect the surface of the substrate.

[0074] 2. Calculation of velocity at the exit of coaxial magnetron plasma accelerating electrode under different N2 pressures The trajectory of titanium plasma at the exit of a coaxial magnetron plasma accelerating electrode under different N2 pressures was captured using an i-SPEED 726 high-speed camera. The initial velocity of the plasma jet was calculated based on the leading-edge displacement of the plasma jet in two consecutive frames at the accelerating electrode exit, with a time interval of 7 μs between the selected two adjacent frames.

[0075] Figure 1 The initial velocity statistics of titanium plasma jets at the exit of the coaxial magnetron plasma accelerating electrode under different N2 pressures in Examples 1-4 are presented. Figure 1 As can be seen, within the N2 pressure range used in this invention, titanium plasma can be ejected at high speed from the coaxial magnetron plasma accelerating electrode outlet, and its initial velocity is greater than 2.0 km / s, indicating that the method of this invention can generate titanium plasma jets with high kinetic energy. High-speed titanium plasma jets are beneficial for enhancing the impact, spreading, diffusion, and reaction processes between deposited particles and the substrate surface, thereby promoting the formation of the titanium nitride coating and its bonding with the substrate.

[0076] 3. High-speed photographic observation of titanium plasma jet under 0.10 MPa N2 pressure The jetting and transport process of the titanium plasma jet in Example 3 was further observed using an i-SPEED 726 high-speed camera.

[0077] Figure 2 The images shown are high-speed photographs of the titanium plasma jet at different times under a pressure of 0.10 MPa N2 in Example 3. (a) is 0 μs, (b) is 21 μs, (c) is 42 μs, (d) is 63 μs, (e) is 84 μs, and (f) is 105 μs, meaning the time interval between adjacent images is 21 μs. Figure 2 It can be seen that after pulsed discharge, the titanium plasma jet is rapidly ejected from the coaxial magnetron plasma accelerating electrode and continuously transported forward along the axial direction. As time goes on, the leading edge of the plasma jet continuously advances towards the substrate, indicating that the TA2 industrial pure titanium cylindrical accelerating electrode can generate a high-speed titanium plasma jet during pulsed discharge, providing a material source and energy input for subsequent in-situ reaction with N2 and deposition of a titanium nitride coating on the substrate surface.

[0078] 4. XRD testing of the coating The titanium nitride coating samples prepared in Examples 1-4 were subjected to wire electrical discharge machining (EDM), and the coating surfaces were sequentially polished with 400-grit, 800-grit, 1500-grit, and 2000-grit sandpaper to obtain samples for X-ray phase analysis. Subsequently, the coatings prepared in Examples 1-4 were analyzed for phase composition using a Bruker D8 X-ray diffractometer, where the horizontal axis represents the diffraction angle 2θ and the vertical axis represents the diffraction intensity.

[0079] Figure 3 The images show the XRD patterns of the titanium nitride coatings prepared in Examples 1-4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Figure 3 It can be seen that TiN phase and Ti(N)-related phase were detected in the coatings prepared in Examples 1-4, indicating that the titanium plasma generated by the TA2 industrial pure titanium accelerating electrode can react with nitrogen in situ in a nitrogen-containing atmosphere and form a Ti-N / titanium nitride coating on the surface of the TC4 titanium alloy substrate. Among them, the diffraction characteristics of the TiN phase in the coating were more obvious under the pressure of 0.10 MPa N2 in Example 3, indicating that the titanium plasma transport process and the in-situ titanium-nitrogen reaction process were well matched under this pressure condition.

[0080] 5. Morphological observation of the cross-section after grinding and polishing The titanium nitride coatings prepared in Example 3 and Comparative Example 2 were segmented using wire electrical discharge machining to obtain test samples. The samples were then embedded with cold mounting material to expose the coating cross-section. Subsequently, the cross-section was polished sequentially with 400-grit, 800-grit, 1200-grit, 1500-grit, and 2000-grit sandpaper until the cross-section showed uniform scratches. Next, it was polished sequentially with 9μm, 1μm, and 0.04μm diamond polishing fluids until the cross-section was essentially free of noticeable scratches. The morphology of the coating cross-section was then observed using a Fermatologic Emission Spectrometer (FEMA).

[0081] Figure 4 This is a morphological image of the cross-section of the titanium nitride coating prepared in Example 3. Figure 4 As can be seen, the coating prepared in Example 3 formed a continuous deposition layer on the surface of the TC4 titanium alloy substrate, with a relatively clear bonding interface between the coating and the substrate, and no obvious through cracks or large-area peeling was observed at the interface. This result indicates that under a pressure of 0.10 MPa N2, the in-situ reaction between titanium plasma and nitrogen can form a relatively complete titanium nitride coating on the substrate surface.

[0082] Figure 5 The image shows the morphology of the coating cross-section prepared in Comparative Example 2. The results indicate that when Comparative Example 2 uses externally added titanium nitride powder as the material input source, the coating prepared by simultaneous powder feeding contains numerous incompletely melted particles (i.e., unmelted titanium nitride particles) and localized areas of uneven structure. In contrast, Example 3 of this invention uses a TA2 industrial pure titanium cylindrical accelerating electrode as the titanium source, and forms a titanium nitride coating through in-situ reaction of titanium plasma with nitrogen in a nitrogen-containing atmosphere. This eliminates the need for externally added titanium nitride powder, which helps reduce the problems of unmelted particles and uneven structure caused by insufficient powder melting.

[0083] 6. Observation of cross-sectional metallographic structure The cross-section of the titanium nitride coated sample prepared in Example 3 was observed using metallographic microstructure. The specific method was as follows: the polished cross-section sample was chemically etched using Keller's reagent with a volume ratio of HF, HNO3 and H2O of 3:5:92 and an etching time of approximately 15 s. Subsequently, the metallographic microstructure of the coated cross-section was observed using a Fermatological Microscope (FEMA).

[0084] Figure 6 The images show the microstructure of the titanium nitride coating prepared in Example 3 after chemical etching. (a1) shows the overall morphology of the coating cross-section, (a2) is a magnified microstructure of region I, (a3) ​​is a magnified microstructure of region II, and (a4) is a magnified microstructure of region III. Figure 6It can be seen that the coating cross-section prepared in Example 3 has a relatively continuous microstructure, with fine microstructure features observed in different regions, and a transitional feature exists in the coating-substrate bonding area. This result indicates that, under the preparation conditions of the present invention, after titanium plasma undergoes an in-situ reaction in a nitrogen-containing atmosphere, a Ti-N / titanium nitride coating with a certain degree of microstructure continuity can be formed on the surface of a TC4 titanium alloy substrate.

[0085] 7. Analysis of Ti and N element distribution in the coating The elemental distribution of the titanium nitride coating prepared in Example 3 was analyzed using a Shimadzu EPMA-8050 G microscope to observe the distribution of Ti and N elements within the coating area.

[0086] Figure 7 The images show the Ti and N element distributions in the central region of the titanium nitride coating prepared in Example 3, where (a) shows the overall morphology of the central region of the titanium nitride coating, (b) shows the Ti element distribution, and (c) shows the N element distribution. Figure 7 It can be seen that both Ti and N elements are distributed within the coating area, indicating that the titanium plasma generated by the TA2 industrial pure titanium accelerating electrode undergoes an in-situ reaction with nitrogen in a nitrogen-containing atmosphere, forming a Ti-N coating region on the substrate surface. Furthermore, the Ti and N elements exhibit a continuous distribution throughout the observation area, further demonstrating that the method of this invention is advantageous for obtaining a titanium nitride coating with a relatively continuous compositional distribution.

[0087] 8. Average microhardness test of coating The microhardness of the titanium nitride coatings prepared in Examples 1-4 was tested using a Fermat Vickers hardness tester (Fness V02625A) according to standard GB / T 4340.1-2024. During testing, the experimental force was 0.025 kgf (25 gf, approximately 0.245 N), and the holding time was 10 s. Multiple test points were selected within each coating cross-section for testing, and the average microhardness of the coating was calculated. The test results are expressed as HV0.025.

[0088] Figure 8 This is a statistical chart showing the average microhardness of the titanium nitride coatings prepared in Examples 1-4 and Comparative Example 1. Figure 8It can be seen that the average microhardness HV0.025 of Examples 1-4 is all above 516.9, while the average microhardness HV0.025 of the TC4 titanium alloy substrate in Comparative Example 1 is only 323.9. The titanium nitride coatings prepared in Examples 1-4 all exhibit a higher hardness level than the TC4 titanium alloy substrate, indicating that the Ti-N / titanium nitride coating prepared by the method of this invention can effectively improve the surface hardness of titanium alloys. Among them, the average microhardness HV0.025 of Example 3 can reach as high as 713.8, which shows that the coating prepared under the 0.10MPa N2 pressure condition used in Example 3 has better structural stability and comprehensive performance.

[0089] In this embodiment of the invention, the transport state of titanium plasma and the degree of titanium-nitrogen reaction in a nitrogen-containing atmosphere can be adjusted by regulating the nitrogen pressure. When the nitrogen pressure is too low, the reaction between the titanium plasma and nitrogen is insufficient, resulting in incomplete titanium nitride formation. When the nitrogen pressure is too high, the collisions, scattering, and thermal effects on the titanium plasma during transport are enhanced, potentially affecting the continuous deposition and uniformity of the coating. Using the nitrogen pressure ranges in Examples 1-4 of this invention is beneficial for achieving a synergistic match between titanium plasma transport and titanium-nitrogen reaction, resulting in titanium nitride coatings with high bonding strength and good wear resistance.

[0090] In embodiments 1-4 of this invention, by controlling the charging voltage and capacitance value of the capacitor energy storage unit, a stable energy input can be provided for the generation and axial acceleration of titanium plasma, which is beneficial for forming a high-speed titanium plasma jet and achieving coating deposition.

[0091] Furthermore, in embodiments 1-4 of this invention, there is a suitable distance between the accelerating electrode outlet and the substrate surface, such as 300 mm. By adjusting this distance, the speed, temperature, diffusion range, and reaction degree of the titanium plasma reaching the substrate surface can be controlled. Using the distance range of this invention (e.g., 200-400 mm) is beneficial for obtaining a titanium nitride coating with good deposition continuity and a more uniform structure. When the deposition distance is too small, the substrate surface experiences a stronger instantaneous thermal shock, resulting in more pits on the coating surface. When the deposition distance is too large, the energy attenuation and divergence of the titanium plasma jet during transport are enhanced, leading to a decrease in coating deposition continuity.

[0092] The titanium nitride coatings provided in Examples 1-4 of this invention can be used to prepare structural parts with long service life and good wear resistance, and have wide applications in high-end equipment manufacturing fields such as aerospace, precision machinery, mold manufacturing, energy equipment, marine equipment or biomedical devices.

[0093] In summary, this invention employs a coaxial magnetron plasma acceleration method, using industrial pure titanium accelerating electrodes and nitrogen-containing gas as specific material input sources to form a titanium plasma jet. The high-speed, highly reactive titanium plasma jet enhances the impact, spreading, diffusion, and reaction processes between deposited particles and the substrate surface, promoting coating densification and stable bonding between the coating and the substrate. This results in a titanium nitride coating with high bonding strength and good wear resistance.

Claims

1. A method for preparing a titanium nitride coating, characterized in that, Includes the following steps: A coaxial magnetron plasma acceleration method is used, with industrial pure titanium as the accelerating electrode material, to perform pulsed discharge, and the accelerating electrode material generates titanium plasma. The titanium plasma forms a titanium plasma jet from the accelerating electrode outlet under the action of electromagnetic force; the titanium plasma jet reacts with nitrogen-containing gas to deposit the titanium nitride coating on the substrate surface.

2. The preparation method according to claim 1, characterized in that, The nitrogen-containing gas includes nitrogen gas; the pressure of the nitrogen gas is 0.04~0.15 MPa.

3. The preparation method according to claim 1, characterized in that, The pulse discharge is powered by a capacitor energy storage unit; the charging voltage of the capacitor energy storage unit is 3~4kV; and / or, the capacitance value of the capacitor energy storage unit is 7.2~20mF.

4. The preparation method according to claim 1, characterized in that, The titanium plasma is formed by Z-pinch and axial acceleration in the coaxial magnetron plasma acceleration method to form the titanium plasma jet; And / or, the initial velocity of the titanium plasma jet at the outlet of the accelerating electrode is ≥2.0 km / s.

5. The preparation method according to claim 1, characterized in that, The industrial pure titanium is used as the cylindrical accelerating electrode material for the coaxial magnetron plasma acceleration method. And / or, the purity of the industrially pure titanium is ≥99.0%.

6. The preparation method according to claim 1, characterized in that, Before performing the pulse discharge, the process further includes a step of preheating the substrate; the preheating temperature is 200~300℃. And / or, the distance from the accelerating electrode outlet to the surface of the substrate is 200~400mm; And / or, the substrate includes a titanium substrate or a titanium alloy substrate.

7. A titanium nitride coating prepared by any one of claims 1 to 6.

8. The titanium nitride coating according to claim 7, characterized in that, The titanium nitride coating has at least one of the following characteristics: 1) The phase composition of the titanium nitride coating includes at least one of TiN phase, Ti(N) phase or α-Ti phase; 2) The Ti and N elements in the titanium nitride coating are continuously or gradient distributed along the coating cross section; 3) The microstructure of the titanium nitride coating is a continuous and dense microstructure; 4) The titanium nitride coating includes at least one of a TiN enrichment region, a Ti(N) transition region, or a titanium nitride reaction layer; 5) The titanium nitride coating forms a metallurgical bond, diffusion bond, or reactive bond with the substrate; 6) The tensile bond strength between the titanium nitride coating and the substrate is greater than or equal to 65 MPa; 7) The microhardness of the titanium nitride coating is higher than that of the substrate.

9. A structural component, characterized in that, The structural component includes a substrate and a titanium nitride coating disposed on the surface of the substrate; the titanium nitride coating is prepared by the preparation method according to any one of claims 1 to 6, or the titanium nitride coating is the titanium nitride coating according to claim 7 or 8.

10. The application of a preparation method as described in any one of claims 1 to 6, or the titanium nitride coating as described in claim 7 or 8, or the structural component as described in claim 9, in the fields of aerospace, precision machinery, mold manufacturing, energy equipment, marine equipment, or biomedical devices.

Images