Micro-deformation, high-wear-resistance and impact-resistance plasma nitriding method for titanium alloy transmission part

Abstract

The invention discloses a micro-deformation high-wear-resistant shock-resistant plasma nitriding method for a titanium alloy transmission part, which belongs to the technical field of titanium alloy material surface treatment, and comprises the working procedures of ultrasonic cleaning, heating cleaning, glow ion cleaning activation, plasma nitriding, furnace cooling and the like. Through a glow discharge plasma process, an N element is bombarded and infiltrated into the surface layer of a Ti alloy matrix in the form of active microparticles. And the adjusting interval of the component proportion of the process gas is 1: 9-3: 7. The plasma nitriding layer prepared through the method does not affect the dimensional precision of the part, meanwhile, the abrasion resistance of the titanium alloy transmission part can be greatly improved, the impact resistance of the titanium alloy transmission part can be remarkably improved, and therefore the service life of the titanium alloy transmission part is greatly prolonged.

Description

Technical Field

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

[0002] Under the general trend of equipment lightweight development, titanium alloy, as a metal material with the highest specific strength and excellent corrosion resistance, has received more and more attention and application. It has a variety of performance advantages, but due to the insufficient hardness of the material, titanium alloy transmission parts perform poorly under high load and large impact conditions. For the sake of structural weight reduction and corrosion resistance, the material selection of transmission parts of many equipment power systems has gradually changed from traditional steel materials to titanium alloys. Improving the wear resistance and impact resistance of titanium alloy parts has become an urgent need. Take a titanium alloy transmission external spline as an example. As a key component for transmitting torque in the power mechanism, the spline is simple and compact, easy to assemble and disassemble, with a large connection area, strong load-bearing capacity, excellent centering and guiding properties. Its quality and life are directly related to the operation of the power mechanism and have an important impact on the overall performance of the equipment system. The spline always bears a large torque load during service, accompanied by a considerable friction effect. In some power units with frequent start-stop, it will also be severely impacted by repeated impact. It is necessary to take technical means to effectively harden and modify its surface.

[0003] For the surface hardening modification of titanium alloys, the common technical means currently include micro-arc oxidation, thermal spraying and physical vapor deposition, but due to the difficulty in controlling dimensional accuracy or insufficient coating bonding strength, the above methods cannot meet the working 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, and effectively improve their wear resistance. At the same time, it provides sufficient impact resistance and bearing capacity, which can significantly improve the service life of titanium alloy transmission parts, so as 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 respectively, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry its surface with dry compressed air;

[0008] 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 furnace chamber is closed for vacuum treatment. When the vacuum degree is ≤5Pa, the heater is turned on to heat to 250℃ and then kept warm for 20 minutes to vaporize the residual grease and other volatile substances on the surface of the workpiece and discharge them from the furnace chamber. Then the surface of the workpiece is 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-keeping-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 the workpiece cools down with the furnace;

[0012] 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 process of nitriding 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 the slender workpiece, it is arranged to be freely suspended in the furnace chamber to control the deformation of the workpiece.

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

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

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

[0017] S403: Maintain the flow ratio of H2 to NH3 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 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 titanium alloy grade and the performance index requirements. The values ​​of the relevant characteristic temperature, time and gas flow rate ratio will be different within the range.

[0019] Furthermore, the limiting 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 manner.

[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 nitriding 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 plasma nitriding method for titanium alloy transmission parts with micro-deformation, high wear resistance and impact resistance of the present invention. The conventional plasma nitriding process generally uses a single heat source plasma furnace, and the maximum nitriding temperature that can be achieved is lower than 700°C. The nitriding layer prepared for the titanium alloy workpiece generally has the disadvantage of uneven nitriding, which is intuitively manifested as the inability to achieve uniform TiN yellow on the workpiece surface; and the nitriding 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 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 method for plasma nitriding with micro-deformation, high wear resistance and impact resistance on the surface of titanium alloy transmission parts of the present invention. When ordinary plasma nitriding process is applied to titanium alloy, the obtained nitriding 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 nitriding layer when the workpiece is in service. Generally, it can only be used in small load friction conditions. The nitriding 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 nitriding layer and the matrix are tightly and firmly combined, and there is ample toughness reserve, which can be applied to various harsh working conditions, especially in high load and large impact occasions.

[0025] 3. The plasma nitriding method for titanium alloy transmission parts with micro-deformation and high wear resistance and impact resistance of the present invention. The conventional plasma nitriding process applied to titanium alloy usually results in a deformation rate of more than 0.5‰, which cannot be used for workpieces with high dimensional accuracy requirements. The present invention can ensure that the dimensional limit deformation rate of the titanium alloy workpiece after nitriding is no more than 0.2‰ by accurately controlling the heating rate and designing the high nitrogen-hydrogen ratio and low nitrogen-hydrogen ratio step-diffusion process, and can be widely used in 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 value distribution diagram of the titanium alloy component after nitriding on the surface of the present invention;

[0028] Figure 3 This is a comparison diagram 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 the 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 nitriding layer of the titanium alloy transmission parts after nitriding in the embodiment of the present invention and the comparative example;

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

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-2 In the 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, wherein the titanium alloy parts need to complete stress relief annealing in accordance with national standards before nitriding, and the specific technical status is as follows:

[0034] 1) The surface of titanium alloy transmission parts before nitriding is bright silver titanium metal color, and the surface of 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) According to GB / T 11354-2005 "Detection of Nitriding Layer Depth and Metallographic Structure of Steel Parts", the depth of nitriding layer of titanium alloy transmission parts after nitriding is controlled within 50-300μm;

[0037] (4) After nitriding, the dimensional deformation of titanium alloy transmission parts in each dimension 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 N element into the surface layer of Ti alloy matrix in the form of active particles through a glow discharge plasma process; and the process gas component ratio is adjusted in the range of 1:9 to 3:7, specifically comprising 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 respectively, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry its 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 in the plasma furnace chamber. The plasma furnace is a controllable electric pulse built-in multi-heat source high-power plasma nitriding furnace; the furnace chamber is closed for vacuum treatment. When the vacuum degree is ≤5Pa, the heater is turned on to heat 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, and then the workpiece surface is 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-keeping-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 the workpiece cools down with the furnace;

[0044] 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 process of nitriding the surface of the titanium alloy workpiece.

[0045] In the embodiment of the present invention, the nitrided parts are titanium alloy substrate, nitrogen diffusion layer and nitride layer from inside to outside, and 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 inside to outside, the microhardness increases gradually, and 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 selection of suitable tooling. The material must be titanium or titanium alloy. Generally, industrial pure titanium TA2 material is selected. The tooling must be scientifically and reasonably designed and manufactured. For slender workpieces, it is necessary to set it 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, keeping the flow ratio of H2 to NH3 at 1:9 until the furnace chamber pressure is maintained at 280-300 Pa, heating to 350-430°C at 35-40°C / h, and then keeping warm for 3h;

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

[0050] S403: Maintain the flow ratio of H2 to NH3 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 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 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 limit size deformation rate of the entire titanium alloy workpiece after nitriding is not more than 0.2‰, and 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 selected transmission external splines are of exactly the same material, form and size, and are uniformly rectangular tooth external splines made of TC4 material. Stress relief annealing treatment has been performed according to national standards before fine machining. The surface hardness of the substrate 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] Embodiment 1:

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

[0055] 1) Ultrasonic cleaning: Check the appearance of the titanium alloy external spline, remove the 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 integrity checks on the equipment cooling water circulation system, furnace air tightness, and process gas pipelines in advance; then place the cleaned and dried titanium alloy external spline vertically in the middle of the workbench plane of the chamber, and 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 turn on the heater to start heating when the furnace chamber vacuum degree is ≤5Pa, and keep warm for 20 minutes after reaching 250℃, so that the residual grease and other volatile substances on the surface of the external spline are vaporized and discharged from the furnace chamber, and the surface of the titanium alloy external spline is further cleaned;

[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 about 290Pa, 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 synchronously: first, NH3 is introduced until the furnace chamber pressure is maintained at about 290Pa, the flow ratio of H2 and NH3 is maintained at 1:9, the temperature is increased to 400℃ at 35℃ / h, and the temperature is kept for 3h; then the flow ratio of H2 and NH3 is adjusted to 3:7, the temperature is controlled to increase to 750℃ at 28℃ / h, and the temperature is kept for 22h; 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 the temperature is kept 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, thus completing the entire process of surface modification.

[0060] Embodiment 2:

[0061] This embodiment is basically the same as the first embodiment, and 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 the 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 integrity checks on the equipment cooling water circulation system, furnace air tightness, and process gas pipelines in advance; then place the cleaned and dried titanium alloy external spline vertically in the middle of the workbench plane of the chamber, and 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 turn on the heater to start heating when the furnace chamber vacuum degree is ≤5Pa, and keep warm for 15 minutes after reaching 250℃, so that the residual grease and other volatile substances on the surface of the external spline are vaporized and discharged from the furnace chamber, and the surface of the titanium alloy external spline is further cleaned;

[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 synchronously: first, NH3 is introduced until the furnace chamber pressure is maintained at about 300Pa, the flow ratio of H2 and NH3 is maintained at 1:9, the temperature is increased to 400℃ at 35℃ / h, and the temperature is kept for 3h; then the flow ratio of H2 and NH3 is adjusted to 3:7, the temperature is controlled to increase to 730℃ at 30℃ / h, and the temperature is kept 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 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, thus completing the entire process of surface modification.

[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 those in Example 1.

[0069] Comparative Example 2:

[0070] 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, 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 3h insulation in the heating stage and the 3h insulation in the cooling stage are cancelled. In addition, all the process steps and parameters are consistent with Example 1.

[0073] Performance Test:

[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 measurement, surface hardness and nitriding layer depth detection, and pulsed 10000N·m instantaneous torque impact test was performed with reference to the actual working conditions of the external splines. The spline teeth were checked every 100 impacts, and the number of impacts when the spline teeth showed obvious damage was recorded. The relevant data are 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 outer spline size deformation is too large, it cannot be properly matched and installed with the matching inner spline impeller, and it no longer has the function of use, so the impact resistance test was not carried out.

[0077] like Figure 3-6 As shown, by comparing and analyzing the relevant data in the table, it can be seen that the surface nitriding layer of the titanium alloy transmission parts prepared by the present invention can not only effectively control the dimensional deformation of the external spline in the embodiment during the nitriding process due to its unique process design, 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 the large torque load 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 surface nitriding layer of the titanium alloy transmission parts prepared by the present invention has better service performance, has a broader market prospect, and is more suitable for technology promotion.

[0078] In the description of this specification, the description of the term "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representation of the term does not necessarily refer to the same embodiment. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments in a suitable manner.

[0079] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made in the specific implementation according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for micro-deformation, high wear resistance and impact resistance plasma nitriding of titanium alloy transmission parts, 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 respectively, then ultrasonically clean it with deionized water for 5 to 10 minutes, and then dry its surface with dry compressed air; 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 furnace chamber is closed for vacuum treatment. When the vacuum degree is ≤5Pa, the heater is turned on to heat to 250℃ and then kept warm for 20 minutes to vaporize the residual grease and other volatile substances on the surface of the workpiece and discharge them from the furnace chamber. Then the surface of the workpiece is cleaned; 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; 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-keeping-cooling control program, and the flow ratio of H2 and NH3 is controlled and adjusted at the same time; S5: Turn off the glow, turn off the gas, turn off the heat source, keep the vacuum pump on, and the workpiece cools 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 process of nitriding the surface of the titanium alloy workpiece.

2. A method for micro-deformation, high wear resistance and impact resistance plasma nitriding of titanium alloy transmission parts 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, the tooling is arranged to be freely suspended in the furnace chamber to control the deformation of the workpiece.

3. A method for micro-deformation, high wear resistance and impact resistance plasma nitriding of titanium alloy transmission parts according to claim 1, characterized in that: The temperature control adjustment process in S4 is as follows: S401: introducing NH3, keeping the flow ratio of H2 to NH3 at 1:9 until the furnace chamber pressure is maintained at 280-300 Pa, heating to 350-430°C at 35-40°C / h, and then keeping warm for 3h; S402: Adjust the flow ratio of H2 to NH3 to 3:7, control the temperature to 720-800°C at 25-30°C / h, and keep it warm for 10-25h; S403: Maintain the flow ratio of H2 to NH3 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 warm for 3 hours, then turn off the glow, turn off the gas, and turn off the heat source.

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

5. A method for micro-deformation, high wear resistance and impact resistance plasma nitriding of titanium alloy transmission parts according to claim 1, characterized in that: The limiting 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 manner.

6. A method for micro-deformation, high wear resistance and impact resistance plasma nitriding of titanium alloy transmission parts according to claim 1, characterized in that: The plasma furnace is a controllable electric pulse built-in multi-heat source high-power plasma nitriding furnace.

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

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