A micro-deformation, high-wear-resistant and impact-resistant plasma nitriding method for titanium alloy transmission parts

Abstract

The present invention discloses a method for producing micro-deformation, highly wear-resistant and impact-resistant plasma nitriding for titanium alloy transmission parts. This method belongs to the field of titanium alloy surface treatment technology and includes ultrasonic cleaning, heating and cleaning, glow ion cleaning and activation, plasma nitriding, and furnace cooling. The method uses H2 and NH3 as process gases, and through a glow discharge plasma process, nitrogen is bombarded and infiltrated into the surface layer of the Ti alloy matrix in the form of active microparticles. The process gas composition ratio is adjusted within a range of 1:9 to 3:7. The plasma nitrided layer produced by the present invention does not affect the dimensional accuracy of the components. It significantly enhances the wear resistance and impact resistance of titanium alloy transmission components, thereby significantly extending the service life of the components.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy material surface treatment, in particular to a micro-deformation, high-wear-resistant and impact-resistant plasma nitriding method for titanium alloy transmission parts. Background Art

[0002] As equipment lightweighting continues, titanium alloys, known for their highest specific strength and excellent corrosion resistance, are gaining increasing attention and application. Despite their numerous performance advantages, titanium alloy transmission components perform poorly under high loads and high impact conditions due to their insufficient hardness. To reduce structural weight and improve corrosion resistance, many equipment powertrain transmission components are gradually shifting from traditional steel to titanium alloys. Improving the wear and impact resistance of titanium alloy components has become an urgent need. For example, titanium alloy transmission external splines, a key component for transmitting torque in powertrains, are simple and compact, easy to assemble and disassemble, with a large connection area, strong load-bearing capacity, and excellent centering and guiding properties. Their quality and lifespan are directly linked to the operation of the powertrain and significantly impact the overall performance of the equipment system. Throughout their service life, splines are subjected to significant torque loads, accompanied by considerable friction. In some powertrains with frequent starts and stops, they are also subject to severe repeated impact. Technical measures are needed to effectively harden and modify their surfaces.

[0003] For the surface hardening modification of titanium alloys, the common technical means currently include micro-arc oxidation, thermal spraying and physical vapor deposition. However, due to the difficulty in controlling dimensional accuracy or insufficient coating adhesion, the above methods cannot meet the working conditions requirements of titanium alloy transmission components in high-precision, high-load and high-impact situations. Summary of the Invention

[0004] The purpose of the present invention is to provide a micro-deformation, highly wear-resistant and impact-resistant plasma nitriding method for titanium alloy transmission parts, which uses a controllable electric pulse built-in multi-heat source high-power plasma furnace to prepare a nitriding layer on the surface of the parts, strictly control the dimensional deformation of the titanium alloy transmission parts, greatly improve the surface hardness of the parts, effectively improve their wear resistance, and at the same time provide sufficient impact bearing capacity, which can significantly improve the service life of titanium alloy transmission parts to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance, comprising the following steps:

[0007] S1: Ultrasonic cleaning: Place the titanium alloy workpiece after deburring and rust removal in an ultrasonic cleaning tank, and ultrasonically clean it with acetone and anhydrous ethanol for 10 to 20 minutes each, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry the surface with dry compressed air;

[0008] S2: Heating and cleaning: After cleaning and drying, the workpiece is equipped with appropriate tooling and placed on the workbench of the plasma furnace chamber. The furnace chamber is closed and vacuumed. When the vacuum degree is ≤5Pa, the heater is turned on and heated to 250°C and then kept warm for 20 minutes to vaporize the residual grease and other volatile substances on the workpiece surface and discharge them from the furnace chamber. The workpiece surface is then cleaned.

[0009] S3: Glow ion cleaning and activation: Introduce H2, turn on the glow when the gas pressure is less than 20Pa, implement ion bombardment and sputtering, clean the workpiece surface and activate the surface, the time is 20 to 30 minutes;

[0010] S4: Plasma nitriding: First, NH3 is introduced into the plasma furnace chamber, and the gas pressure range is controlled to be 280-300Pa. Then, the temperature is controlled and adjusted according to the set heating-maintaining-cooling control program, and the flow ratio of H2 and NH3 is controlled and adjusted at the same time;

[0011] S5: Turn off the glow, turn off the gas, turn off the heat source, keep the vacuum pump on, and let the workpiece cool down with the furnace;

[0012] S6: When the temperature of the workpiece drops to less than 80°C, open the plasma nitriding furnace chamber and take out the titanium alloy workpiece, thus completing the entire nitriding process on the surface of the titanium alloy workpiece.

[0013] Furthermore, the tooling in S2 is made of titanium or titanium alloy, and the structural design of the tooling is adapted to the workpiece. For slender workpieces, the tooling is arranged to be freely suspended in the furnace chamber to control the deformation of the workpiece.

[0014] Furthermore, the temperature control and adjustment process in S4 is as follows:

[0015] S401: introducing NH3, maintaining the flow ratio of H2 to NH3 at 1:9 until the furnace chamber pressure is maintained at 280-300 Pa, then heating to 350-430°C at 35-40°C / h, and then keeping warm for 3 hours;

[0016] S402: Adjust the H2 to NH3 flow ratio to 3:7, control the temperature to 720-800°C at 25-30°C / h, and keep it at this temperature for 10-25h;

[0017] S403: Maintain the H2 to NH3 flow ratio of 3:7, keep the vacuum pump on, turn off the auxiliary heat source, control the furnace chamber temperature to drop to 350-400℃ and keep it warm for 3 hours, then turn off the glow, turn off the gas, and turn off the heat source.

[0018] Furthermore, the temperature and gas flow rate of the nitriding furnace chamber in S4 are controlled according to the size of the nitriding workpiece, the grade of titanium alloy and the performance index requirements. The values ​​of the relevant characteristic temperature, time and gas flow rate ratio within the range will be different.

[0019] Furthermore, the limit size deformation rate of the titanium alloy workpiece in S6 after nitriding is no more than 0.2‰, and the nitrided layer on the workpiece surface includes a titanium alloy matrix, a nitrogen diffusion layer and a nitride layer from the inside to the outside, and the microhardness increases in a gradient.

[0020] Furthermore, the plasma furnace is a controllable electric pulse built-in multi-heat source high-power plasma nitriding furnace.

[0021] Furthermore, the thickness of the nitrided layer on the workpiece surface can be controlled within the range of 50 to 300 μm, the N content increases gradually from the inside to the outside, and the microhardness of the outer surface is controlled within the range of 700 to 1000 HV. 0.1 .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention provides a method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance. Conventional plasma nitriding processes generally use a single heat source plasma furnace, and the maximum nitriding temperature that can be achieved is lower than 700°C. The nitrided layer prepared for titanium alloy workpieces generally has the disadvantage of uneven nitriding, which is intuitively manifested as the inability to achieve a uniform TiN yellow color on the workpiece surface; the nitrided layer is very shallow, generally less than 30μm; the surface hardness value is small and unevenly distributed, usually less than 600HV 0.1 The present invention adopts a controllable electric pulse built-in multi-heat source high-power plasma furnace, and the furnace chamber can achieve a maximum temperature of 900°C. By implementing the process steps proposed by the present invention, a uniform and consistent nitriding layer can be obtained on the surface of the titanium alloy workpiece, the depth of the nitriding layer can reach 50 to 300 μm, and the surface hardness can reach 700 to 1000 HV. 0.1 .

[0024] 2. The present invention provides a method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance. When ordinary plasma nitriding process is applied to titanium alloy, the obtained nitrided layer is too shallow and the hardness gradient transition between the outer surface and the matrix cannot be achieved, which easily leads to peeling of the nitrided layer when the workpiece is in service and can generally only be used in small load friction conditions. The nitrided layer prepared by the present invention has sufficient thickness, and the hardness between its outer surface and the titanium alloy matrix is ​​gradiently transitioned. The nitrided layer and the matrix are tightly and firmly bonded, and have sufficient toughness reserve, which can be applied to various harsh working conditions, especially in high load and large impact occasions. The advantages are very obvious.

[0025] 3. The present invention's plasma nitriding method for titanium alloy transmission parts with micro-deformation, high wear resistance, and impact resistance. Conventional plasma nitriding processes applied to titanium alloys typically result in deformation rates exceeding 0.5‰, making them unsuitable for workpieces requiring high dimensional accuracy. By precisely controlling the heating rate and designing a stepped nitriding process with high and low nitrogen-hydrogen ratios, the present invention ensures that the ultimate dimensional deformation rate of the titanium alloy workpiece after nitriding is no greater than 0.2‰. This method is widely applicable to titanium alloy splines and various titanium alloy precision parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a typical cross-sectional metallographic diagram of the titanium alloy component after nitriding on the surface of the present invention;

[0027] Figure 2 This is a typical cross-sectional hardness distribution diagram of the titanium alloy component after nitriding on the surface of the present invention;

[0028] Figure 3 This is a comparison chart of the deformation rates of titanium alloy transmission parts after nitriding in the embodiments of the present invention and the comparative examples;

[0029] Figure 4 This is a comparison chart of the surface hardness of titanium alloy transmission parts after nitriding in the embodiment of the present invention and the comparative example;

[0030] Figure 5 A comparison diagram of the depth of the nitrided layer of the titanium alloy transmission parts after nitriding in the embodiment of the present invention and the comparative example;

[0031] Figure 6 The figure is a comparison chart of the effective service life of the titanium alloy transmission parts in the embodiment of the present invention and the comparative example after nitriding. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] See also Figure 1-2 In an embodiment of the present invention, a method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance is provided. In this method, the titanium alloy parts must undergo stress relief annealing in accordance with national standards before nitriding. The specific technical status is as follows:

[0034] 1) The surface of the titanium alloy transmission parts before nitriding is silver-bright titanium metal color, and the surface of the parts after nitriding turns into uniform titanium nitride yellow;

[0035] 2) According to GB / T 430.1-2009 "Vickers Hardness Test for Metallic Materials", the surface microhardness of titanium alloy transmission parts after nitriding is controlled at 700-1000HV 0.1 ;

[0036] 3) Refer to GB / T 11354-2005 "Detection of Nitriding Layer Depth and Metallographic Structure of Steel Parts" for testing. After nitriding, the depth of the nitriding layer of titanium alloy transmission parts is controlled within 50-300μm.

[0037] (4) After nitriding, the dimensional deformation of titanium alloy transmission parts is ≤0.2‰, ensuring that the parts can be assembled normally.

[0038] The present invention uses H2 and NH3 as process gas raw materials, and bombards and infiltrates nitrogen element in the form of active particles into the surface layer of the Ti alloy matrix through a glow discharge plasma process. The process gas composition ratio is adjusted in the range of 1:9 to 3:7, and specifically includes the following steps:

[0039] S1: Ultrasonic cleaning: Place the titanium alloy workpiece after deburring and rust removal in an ultrasonic cleaning tank, and ultrasonically clean it with acetone and anhydrous ethanol for 10 to 20 minutes each, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry the surface with dry compressed air;

[0040] S2: Heating and cleaning: The cleaned and dried workpiece is equipped with suitable tooling and placed on the workbench of the plasma furnace chamber. The plasma furnace is a high-power plasma nitriding furnace with controllable electric pulses and built-in multiple heat sources. The furnace chamber is closed and vacuumed. When the vacuum degree is ≤5Pa, the heater is turned on and heated to 250℃ and then kept warm for 20 minutes to vaporize the residual grease and other volatile substances on the workpiece surface and discharge them from the furnace chamber. The workpiece surface is then cleaned.

[0041] S3: Glow ion cleaning and activation: Introduce H2, turn on the glow when the gas pressure is less than 20Pa, implement ion bombardment and sputtering, clean the workpiece surface and activate the surface, the time is 20 to 30 minutes;

[0042] S4: Plasma nitriding: First, NH3 is introduced into the plasma furnace chamber, and the gas pressure range is controlled to be 280-300Pa. Then, the temperature is controlled and adjusted according to the set heating-maintaining-cooling control program, and the flow ratio of H2 and NH3 is controlled and adjusted at the same time;

[0043] S5: Turn off the glow, turn off the gas, turn off the heat source, keep the vacuum pump on, and let the workpiece cool down with the furnace;

[0044] S6: When the temperature of the workpiece drops to less than 80°C, open the plasma nitriding furnace chamber and take out the titanium alloy workpiece, thus completing the entire nitriding process on the surface of the titanium alloy workpiece.

[0045] In the embodiment of the present invention, the nitrided parts are composed of a titanium alloy substrate, a nitrogen diffusion layer and a nitride layer from the inside to the outside. The titanium alloy substrate can be various common grades such as TC4, TC6, TC11, etc. The thickness of the plasma nitriding layer can be controlled at 50 to 300 μm. The N element content gradually increases from the inside to the outside, and the microhardness increases in a gradient. The surface microhardness can reach 700 to 1000 HV. 0.1 .

[0046] In the above S2, in order to prevent impurity elements such as C from contaminating the workpiece, it is strictly forbidden to use materials such as steel for the appropriate tooling used therewith. The material must be titanium or titanium alloy, and industrial pure titanium TA2 material is generally selected. The tooling must be scientifically and reasonably designed and manufactured. For slender workpieces, they must be set to be freely suspended in the furnace chamber to strictly control the deformation of the workpiece.

[0047] The temperature control and adjustment process in the above S4 is as follows:

[0048] S401: introducing NH3, maintaining the flow ratio of H2 to NH3 at 1:9 until the furnace chamber pressure is maintained at 280-300 Pa, then heating to 350-430°C at 35-40°C / h, and then keeping warm for 3 hours;

[0049] S402: Adjust the H2 to NH3 flow ratio to 3:7, control the temperature to 720-800°C at 25-30°C / h, and keep it at this temperature for 10-25h;

[0050] S403: Maintain the H2 to NH3 flow ratio of 3:7, keep the vacuum pump on, turn off the auxiliary heat source, control the furnace chamber temperature to drop to 350-400℃ and keep it warm for 3 hours, then turn off the glow, turn off the gas, and turn off the heat source.

[0051] Among them, the nitriding furnace chamber temperature and gas flow control are different according to the size of the nitriding object workpiece, the titanium alloy grade and the performance index requirements. The relevant characteristic temperature, time and gas flow ratio will have different values ​​within the range; and the maximum size deformation rate of the entire titanium alloy workpiece after nitriding is not greater than 0.2‰. The nitriding layer on the workpiece surface includes titanium alloy matrix, nitrogen diffusion layer and nitride layer from the inside to the outside, and the microhardness increases gradiently.

[0052] In order to further better explain the embodiments of the present invention, the following embodiments and comparative examples are also provided. The material, form and size of the selected transmission external splines are exactly the same, and they are uniformly rectangular tooth external splines made of TC4 material. They have been stress-relief annealed according to national standards before fine machining. The surface hardness of the base is about 320HV. The main dimensions of the external splines are: height 120.00mm, outer diameter 100.00mm, and tooth top spacing 10.50mm.

[0053] Example 1:

[0054] For the TC4 rectangular tooth external spline nitriding in this example, the specific process is as follows:

[0055] 1) Ultrasonic cleaning: Check the appearance of the titanium alloy external spline, remove surface burrs and obvious rust and stains, place the cleaned spline in an ultrasonic cleaning tank, and ultrasonically clean it with acetone and anhydrous ethanol for 15 minutes each, then ultrasonically clean it with deionized water for 5 minutes, and then dry its surface with dry compressed air;

[0056] 2) Heating and cleaning: Use a controllable electric pulse built-in multi-heat source high-power plasma furnace, and conduct a preliminary integrity check on the equipment's cooling water circulation system, furnace body air tightness, and process gas pipelines; then place the cleaned and dried titanium alloy external spline vertically in the middle of the workbench plane of the chamber. Be sure to place it flat to avoid gaps and sharp corners; then close the furnace chamber, turn on the vacuum pump for vacuum treatment, and when the furnace chamber vacuum degree is ≤5Pa, turn on the heater to start heating, and keep it warm to 250℃ for 20 minutes to vaporize the residual grease and other volatile substances on the surface of the external spline and discharge them from the furnace chamber, further cleaning the surface of the titanium alloy external spline;

[0057] 3) Glow ion cleaning and activation: H2 with a purity of not less than 99.9% is introduced into the plasma furnace chamber, and the glow is turned on under the condition of gas pressure less than 20Pa. Ion bombardment and sputtering are performed on the tooth surface of the titanium alloy external spline to clean the surface of the titanium alloy external spline and activate the metal on its surface. The time is 25 minutes;

[0058] 4) Plasma nitriding: NH3 with a purity of not less than 99.9% is introduced into the plasma furnace chamber, the gas pressure is controlled to be around 290Pa, and then the temperature is controlled and adjusted according to the set heating-keeping-cooling control program, and the H2 and NH3 flow ratio is controlled and adjusted simultaneously: first, NH3 is introduced until the furnace chamber pressure is maintained at around 290Pa, and the H2 and NH3 flow ratio is maintained at 1:9, and the temperature is raised to 400℃ at 35℃ / h and kept warm for 3h; then the H2 and NH3 flow ratio is adjusted to 3:7, and the temperature is controlled to rise to 750℃ at 28℃ / h and kept warm for 22h; thereafter, the H2 and NH3 flow ratio is maintained at 3:7, the auxiliary heat source is turned off, and the furnace chamber temperature is controlled to drop to 400℃ and kept warm for 3h; finally, the glow is turned off, the gas is turned off, the heat source is turned off, the vacuum pump is kept on, and the titanium alloy external spline in the furnace chamber is cooled with the furnace;

[0059] 5) When the temperature of the titanium alloy external spline drops to less than 80° C., the plasma nitriding furnace chamber is opened and the titanium alloy external spline is taken out, thereby completing the entire surface modification process.

[0060] Example 2:

[0061] This embodiment is basically the same as the first embodiment. The specific difference between the two is that the relevant technical parameters selected during the plasma nitriding process are different, as follows:

[0062] 1) Ultrasonic cleaning: Check the appearance of the titanium alloy external spline, remove surface burrs and obvious rust and stains, place the cleaned spline in an ultrasonic cleaning tank, and ultrasonically clean it with acetone and anhydrous ethanol for 12 minutes each, then ultrasonically clean it with deionized water for 5 minutes, and then dry its surface with dry compressed air;

[0063] 2) Heating and cleaning: Use a controllable electric pulse built-in multi-heat source high-power plasma furnace, and conduct a preliminary integrity check on the equipment's cooling water circulation system, furnace body air tightness, and process gas pipelines; then place the cleaned and dried titanium alloy external spline vertically in the middle of the workbench plane of the chamber. Be sure to place it flat to avoid gaps and sharp corners; then close the furnace chamber, turn on the vacuum pump for vacuum treatment, and when the furnace chamber vacuum degree is ≤5Pa, turn on the heater to start heating, and keep it warm to 250℃ for 15 minutes to vaporize the residual grease and other volatile substances on the surface of the external spline and discharge them from the furnace chamber, further cleaning the surface of the titanium alloy external spline;

[0064] 3) Glow ion cleaning and activation: H2 with a purity of not less than 99.9% is introduced into the plasma furnace chamber, and the glow is turned on under the condition of gas pressure less than 20Pa. Ion bombardment and sputtering are performed on the tooth surface of the titanium alloy external spline to clean the surface of the titanium alloy external spline and activate the metal on its surface. The time is 25 minutes;

[0065] 4) Plasma nitriding: NH3 with a purity of not less than 99.9% is introduced into the plasma furnace chamber, the gas pressure is controlled to be about 300Pa, and then the temperature is controlled and adjusted according to the set heating-keeping-cooling control program, and the flow ratio of H2 and NH3 is controlled and adjusted simultaneously: first, NH3 is introduced until the furnace chamber pressure is maintained at about 300Pa, and the flow ratio of H2 and NH3 is maintained at 1:9, and the temperature is raised to 400℃ at 35℃ / h and kept warm for 3h; then the flow ratio of H2 and NH3 is adjusted to 3:7, and the temperature is controlled to rise to 730℃ at 30℃ / h and kept warm for 12h; thereafter, the flow ratio of H2 and NH3 is maintained at 3:7, the auxiliary heat source is turned off, and the furnace chamber temperature is controlled to drop to 400℃ and kept warm for 3h; finally, the glow is turned off, the gas is turned off, the heat source is turned off, the vacuum pump is kept on, and the titanium alloy external spline in the furnace chamber is cooled with the furnace;

[0066] 5) When the temperature of the titanium alloy external spline drops to less than 80° C., the plasma nitriding furnace chamber is opened and the titanium alloy external spline is taken out, thereby completing the entire surface modification process.

[0067] Comparative Example 1:

[0068] The difference between this comparative example and Example 1 is that in a method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance, an ordinary plasma nitriding furnace is used with a maximum process temperature of 650°C. In addition, all process steps and parameters are consistent with Example 1.

[0069] Comparative Example 2:

[0070] The difference between this comparative example and Example 1 is that in a method for micro-deformation, high wear-resistant and impact-resistant plasma nitriding of titanium alloy transmission parts, the change in the flow ratio of process gases H2 and NH3 is cancelled, and the flow ratio of the two is always maintained at 1:9. In addition, all process steps and parameters are consistent with Example 1.

[0071] Comparative Example 3:

[0072] The difference between this comparative example and Example 1 is that: in a method for micro-deformation, highly wear-resistant and impact-resistant plasma nitriding of titanium alloy transmission parts, the temperature control during the nitriding process cancels the insulation of the intermediate section of heating and cooling, that is, the 3-hour insulation in the heating stage and the 3-hour insulation in the cooling stage are cancelled. In addition, all process steps and parameters are consistent with Example 1.

[0073] Performance testing:

[0074] The nitrided titanium alloy external splines prepared in Examples 1 and 2 and Comparative Examples 1, 2, and 3 were subjected to dimensional deformation measurements, surface hardness, and nitrided layer depth testing. Furthermore, pulsed 10,000 N·m instantaneous torque shock testing was performed, based on actual external spline operating conditions. The spline teeth were inspected every 100 shocks, and the number of shocks at which significant damage occurred was recorded. The relevant data is as follows:

[0075] Maximum deformation rate Surface hardness Nitriding layer depth Impact resistance Example 1 0.15‰ <![CDATA[865HV 0.1 ]]> 210μm 10200 Example 2 0.10‰ <![CDATA[788HV 0.1 ]]> 85μm 9500 Comparative Example 1 0.05‰ <![CDATA[515HV 0.1 ]]> 25μm 3400 Comparative Example 2 0.20‰ <![CDATA[815HV 0.1 ]]> 65μm 6200 Comparative Example 3 0.45‰ <![CDATA[822HV 0.1 ]]> 155μm ——

[0076] Among them: In comparative example 3, since the external spline size deformation was too large, it could not be properly matched and installed with the matching internal spline impeller, and it no longer had any usable function, so the impact resistance test was not performed.

[0077] like Figure 3-6 As shown, by comparing and analyzing the relevant data in the table, it can be seen that the nitriding layer on the surface of the titanium alloy transmission component prepared by the present invention, due to its unique process design, can not only effectively control the dimensional deformation of the external spline in the embodiment during the nitriding process, greatly improve the surface hardness of the spline teeth, and significantly improve the wear resistance of the spline tooth surface; but also ensure a sufficiently large nitriding layer depth, which can effectively reduce the wear and impact damage of high torque loads on the titanium alloy external spline tooth surface, thereby significantly improving the service life of the external spline. By comparison, it can be seen that the nitriding layer on the surface of the titanium alloy transmission component prepared by the present invention has better service performance, has a broader market prospect, and is more suitable for technology promotion.

[0078] Throughout this specification, the term "embodiment" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment is included in at least one embodiment of the present invention. Schematic representations of this term throughout this specification do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments.

[0079] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations may be made in practice based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance, characterized in that: The following steps are involved: S1: Ultrasonic cleaning: Place the titanium alloy workpiece after deburring and rust removal in an ultrasonic cleaning tank, and ultrasonically clean it with acetone and anhydrous ethanol for 10 to 20 minutes each, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry the surface with dry compressed air; S2: Heating and cleaning: After cleaning and drying, the workpiece is equipped with appropriate tooling and placed on the workbench of the plasma furnace chamber. The furnace chamber is closed and vacuumed. When the vacuum degree is ≤5Pa, the heater is turned on and heated to 250℃ and then kept warm for 20 minutes to vaporize the residual grease and other volatile substances on the workpiece surface and discharge them from the furnace chamber. The workpiece surface is then cleaned. S3: Glow ion cleaning and activation: Introduce H2, turn on the glow when the gas pressure is less than 20 Pa, implement ion bombardment and sputtering, clean the workpiece surface and activate the surface, the time is 20 to 30 minutes; S4: Plasma nitriding: First, NH3 is introduced into the plasma furnace chamber, and the gas pressure range is controlled to be 280-300 Pa. Then, the temperature is controlled and adjusted according to the set heating-maintaining-cooling control program, and the flow ratio of H2 and NH3 is controlled and adjusted at the same time; The temperature control adjustment process is as follows: S401: introducing NH3, maintaining the flow ratio of H2 to NH3 at 1:9 until the furnace chamber pressure is maintained at 280-300 Pa, then heating to 350-430°C at 35-40°C / h, and then keeping warm for 3 hours; S402: Adjust the H2 to NH3 flow ratio to 3:7, control the temperature to 720-800°C at 25-30°C / h, and keep it at this temperature for 10-25h; S403: Maintain the H2 to NH3 flow ratio at 3:7, keep the vacuum pump on, turn off the auxiliary heat source, control the furnace chamber temperature to drop to 350-400°C and keep it there for 3 hours, then turn off the glow, gas, and heat source; S5: Turn off the glow, turn off the gas, turn off the heat source, keep the vacuum pump on, and let the workpiece cool down with the furnace; S6: When the temperature of the workpiece drops to less than 80°C, the plasma nitriding furnace chamber is opened and the titanium alloy workpiece is taken out, thus completing the entire nitriding process on the surface of the titanium alloy workpiece; The plasma furnace is a controllable electric pulse built-in multi-heat source high-power plasma nitriding furnace.

2. The method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance according to claim 1, characterized in that: The tooling in S2 is made of titanium or titanium alloy. The structural design of the tooling is adapted to the workpiece. For slender workpieces, it is set to be freely suspended in the furnace chamber to control the deformation of the workpiece.

3. The method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance according to claim 2, characterized in that: The temperature and gas flow rate control of the nitriding furnace chamber in S4 will vary according to the size of the nitriding workpiece, the grade of titanium alloy and the performance index requirements. The values ​​of the relevant characteristic temperature, time and gas flow rate ratio will vary within the range.

4. The method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance according to claim 1, characterized in that: The limit size deformation rate of the S6 titanium alloy workpiece after nitriding is no more than 0.2‰. The nitrided layer on the workpiece surface includes the titanium alloy matrix, nitrogen diffusion layer and nitride layer from the inside to the outside, and the microhardness increases in a gradient.

5. The method for plasma nitriding of titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance according to claim 4, characterized in that: The thickness of the nitrided layer on the workpiece surface is 50-300 μm, the N content increases gradually from the inside to the outside, and the microhardness of the outer surface is 700-1000 HV 0.1 .

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