Surface strengthening method for titanium-based piston rod part

Abstract

The invention discloses a surface strengthening method for a titanium-based piston rod part. The method comprises the following steps: 1, carrying out stretching deformation treatment on the titanium-based piston rod part to obtain the titanium-based piston rod part after tissue deformation; secondly, isothermal recovery is conducted on the titanium-based piston rod part obtained after tissue deformation, and the titanium-based piston rod part obtained after tissue regulation and control is obtained; and thirdly, the titanium-based piston rod part obtained after structure regulation and control is put into a direct-current pulse ion nitriding furnace, nitriding gas is introduced after vacuumizing, auxiliary heating and a pulse power source are started for heat preservation nitriding, and the titanium-based piston rod part with a nitriding layer on the surface is obtained. According to the method, a deformation recovery and ion nitriding combined method is adopted, the structure is effectively broken and stabilized, more effective channels are provided for diffusion of nitrogen atoms into a matrix in the nitriding process, the nitriding efficiency and the thickness of a nitriding layer are improved, and the wear resistance of a titanium-based piston rod part is enhanced; meanwhile, mechanical properties such as stretching and fatigue of titanium-based piston rod parts are not reduced, and the method is suitable for the field of titanium alloy nitriding.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy surface strengthening, and in particular relates to a surface strengthening method for a titanium-based piston rod part. Background Art

[0002] Thrust vectoring technology achieves the purpose of generating axial force, lateral force and normal force by changing the direction of the aircraft engine tail jet and the nozzle diameter. The lateral force and normal force produce a deflection moment relative to the center of gravity of the aircraft, thereby enabling the aircraft to obtain additional control capabilities in the pitch and yaw directions.

[0003] The vector nozzle relies on the opening and closing of the guide vane to change the thrust size of the nozzle direction, and the power of the guide vane operation comes from the vector actuator unit at the rear. When the actuator unit completes the specified action of the system, the piston rod is not only subjected to the axial force, but also to the deflection torque of the guide vane, resulting in a sliding friction state between the piston rod and the sealing assembly under the support of dynamic load. This requires the surface strengthening treatment of the piston rod to achieve a wear-resistant effect.

[0004] At present, the traditional method of strengthening the piston rod surface is to perform surface electroplating chrome treatment. The chrome plating layer is usually 20μm to 50μm. Since the substrate is titanium alloy, the coating and the substrate are non-metallurgical bonds. During actual use, the film layer also has the risk of peeling and peeling.

[0005] Ion nitriding can significantly improve the surface hardness of titanium alloy substrate. The nitrided layer and the substrate are metallurgically bonded, avoiding the risk of peeling between the nitrided layer and the substrate. At the same time, the thickness of the titanium alloy nitrided diffusion layer can reach more than 80μm, which can effectively serve as a transition support layer. The nitrided layer has excellent wear resistance.

[0006] Traditional titanium alloy nitriding is mainly achieved by glow ion nitriding. The nitriding layer is mainly composed of a titanium nitride ceramic layer deposited on the surface and a supersaturated diffusion phase formed by nitrogen atoms diffusing into the matrix. During the nitriding process, due to the influence of sputtering deposition, nitrogen atoms diffuse into the interior of the matrix, and a titanium nitride ceramic layer is formed on the surface of the substrate. As the nitriding process proceeds, the titanium nitride layer will gradually deposit and thicken. Due to the formation of titanium nitride, the vacant gaps on the surface of the substrate are gradually filled, so that the channel for nitrogen atoms to diffuse inward is severely blocked until it is completely closed. The diffusion of nitrogen atoms mainly depends on the nitrogen potential difference inside and outside the matrix. When the surface nitrogen atoms cannot continue to diffuse into the interior of the matrix, the nitrogen potential difference decreases, the diffusion rate decreases or even drops to zero, making it difficult for the nitriding layer to continue to increase after it grows to a certain extent. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a surface strengthening method for titanium-based piston rod parts in view of the shortcomings of the above-mentioned prior art. The method adopts deformation recovery combined with ion nitriding method to prepare a nitriding layer on the surface of the titanium-based piston rod part, providing more effective channels for nitrogen atoms to diffuse into the matrix during the nitriding process, improving the nitriding efficiency and the thickness of the nitriding layer, enhancing the wear resistance of the titanium-based piston rod part, and solving the problem that the nitriding layer is difficult to increase continuously due to the obstruction of the diffusion channel in the existing nitriding process.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: a surface strengthening method for titanium-based piston rod parts, characterized in that the method comprises the following steps:

[0009] Step 1: tissue deformation: subjecting the titanium-based piston rod part to a tensile deformation treatment to obtain a titanium-based piston rod part after tissue deformation;

[0010] Step 2, tissue control: placing the titanium-based piston rod part after tissue deformation obtained in step 1 into a heat treatment furnace for isothermal recovery, and cooling it to room temperature with the furnace after the recovery to obtain a titanium-based piston rod part after tissue control;

[0011] Step 3, ion nitriding: put the titanium-based piston rod parts after organization control obtained in step 2 into the cathode disk of the DC pulse ion nitriding furnace, turn on the vacuum pump to evacuate, then introduce the nitriding gas, turn on the auxiliary heating and pulse power supply, and gradually increase the pulse voltage and duty cycle. After reaching the nitriding temperature, carry out heat preservation nitriding. After the end, turn off the pulse power supply and auxiliary heating, cool with the furnace to below 100°C and take out to obtain a titanium-based piston rod part with a nitriding layer on the surface.

[0012] The above-mentioned surface strengthening method of a titanium-based piston rod part is characterized in that the maximum tensile deformation of the tensile deformation treatment in step 1 is 20% to 70% of the maximum fracture deformation of the titanium-based piston rod part, and is maintained for 30 minutes to 90 minutes. The range of the tensile deformation ensures that the structure deformation of the titanium-based piston rod part is achieved, and the greater the maximum tensile deformation within the range, the more broken grains there are in the structure, which is more conducive to improving the subsequent ion nitriding efficiency.

[0013] The above-mentioned surface strengthening method of a titanium-based piston rod part is characterized in that, during the tensile deformation treatment in step one, ultrasonic vibration is continuously added until the tensile deformation is completed, the vibration frequency is 10kHz to 40kHz, and after the tensile deformation is completed and the force returns to zero, the titanium-based piston rod part is removed.

[0014] The above-mentioned surface strengthening method of a titanium-based piston rod part is characterized in that the temperature of the isothermal recovery in step 2 is 499°C to 510°C, the heating rate is 3.0°C / min to 10.0°C / min, and the temperature is kept for 60min to 120min after reaching the temperature. This temperature parameter range not only promotes the uniform deformation organization of the titanium-based piston rod part, but also effectively regulates its organizational structure, avoiding the temperature being too low and the regulation effect being little, and the temperature being too high, which easily causes excessive organizational recovery and weakens the organizational deformation effect of the previous tensile deformation treatment.

[0015] The above-mentioned surface strengthening method for a titanium-based piston rod part is characterized in that the process parameters of the thermal insulation nitriding in step three are: power supply frequency 1000Hz~2000Hz, duty cycle 10%~75%, voltage 300V~1000V, vacuum degree 1Torr~8Torr, temperature 700℃~850℃.

[0016] The above-mentioned surface strengthening method of a titanium-based piston rod part is characterized in that in step 3, a plurality of titanium-based piston rod parts after tissue adjustment are placed in a cathode disk with a spacing of more than 30 mm, and a titanium alloy tooling is used to pad them. By controlling the spacing between the parts, the mutual influence of the nitriding processes of the parts is avoided; by using a titanium alloy tooling to pad the parts, the hollow cathode effect is prevented.

[0017] The above-mentioned surface strengthening method for titanium-based piston rod parts is characterized in that the thickness of the nitriding layer in step 3 is 10 μm to 100 μm. The thickness of the nitriding layer obtained by the present invention is better than the thickness range of the nitriding layer of the existing conventional process under the same parameters.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention causes the α phase in the matrix of the titanium-based piston rod part to break through tensile deformation, generates more vacancies and dislocation slip lines, provides more effective channels for nitrogen atoms to diffuse into the matrix during the subsequent ion nitriding process, improves the nitriding efficiency, increases the thickness of the nitriding layer, and enhances the wear resistance of the titanium-based piston rod part.

[0020] 2. The present invention regulates the structure of the titanium-based piston rod parts after tensile deformation through isothermal recovery, thereby ensuring the homogenization of the structure after crushing and achieving the effect of stabilizing the structure, thereby not reducing the mechanical properties such as tensile and fatigue properties of the titanium-based piston rod parts.

[0021] 3. The present invention continuously adds ultrasonic vibration during the tensile deformation process, so that the tensile deformation energy is superimposed on the ultrasonic vibration energy, which can more easily break the grains in the titanium-based piston rod part structure, thereby improving the crushing efficiency and the number of broken crystals.

[0022] 4. The thickness of the nitriding layer prepared on the surface of the titanium-based piston rod part of the present invention is 10μm to 100μm, and at the same nitriding temperature, the nitriding diffusion efficiency of the present invention is higher and the nitriding layer is thicker. Therefore, compared with the traditional nitriding process, the nitriding temperature required for obtaining the same nitriding layer thickness in the present invention is lower, the energy consumption required for the nitriding process is lower, and the energy efficiency is higher.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the metallographic structure diagram of the titanium-based piston rod part before and after the structural deformation regulation in Example 2 of the present invention.

[0025] Figure 2 This is a metallographic image of the nitriding layer prepared on the surface of a titanium-based piston rod part in Example 2 of the present invention.

[0026] Figure 3 This is a cross-sectional hardness gradient diagram of a nitrided layer prepared by microstructure deformation regulation and a nitrided layer prepared without microstructure deformation regulation on the surface of a titanium-based piston rod part in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment includes the following steps:

[0029] Step 1, tissue deformation: the titanium-based piston rod part is subjected to tensile deformation treatment, the tensile strain rate is 0.5 mm / min, the maximum tensile deformation is 20% of the maximum fracture deformation, and it is maintained for 30 minutes, and ultrasonic vibration is continuously added during the tensile deformation treatment until the tensile deformation is completed, the vibration frequency is 10 kHz, and after the tensile deformation is completed and the force returns to zero, the titanium-based piston rod part is removed to obtain the titanium-based piston rod part after tissue deformation;

[0030] Step 2, organization control: the titanium-based piston rod part after organization deformation obtained in step 1 is placed in a heat treatment furnace for isothermal recovery at a temperature of 499°C and a heating rate of 3.0°C / min. After reaching the temperature, the part is kept at this temperature for 60 minutes. After the temperature is reached, the part is cooled to room temperature with the furnace to obtain the titanium-based piston rod part after organization control;

[0031] Step 3, ion nitriding: put the multiple titanium-based piston rod parts after tissue adjustment obtained in step 2 into the cathode disk of the DC pulse ion nitriding furnace with a spacing of more than 30 mm, and use titanium alloy tooling to raise it, turn on the vacuum pump to evacuate to below 10Pa, then introduce high-purity nitrogen, turn on the auxiliary heating and pulse power supply, and gradually increase the pulse voltage and duty cycle. After reaching the nitriding temperature, carry out heat-insulating nitriding. The process parameters of heat-insulating nitriding are: power frequency 1000Hz, duty cycle 10%, voltage 300V, vacuum 8Torr, temperature 700℃. After the end, turn off the pulse power supply and auxiliary heating, cool to below 100℃ with the furnace and take it out to obtain a titanium-based piston rod part with a nitriding layer of 30μm thickness on the surface.

[0032] Example 2

[0033] This embodiment includes the following steps:

[0034] Step 1, tissue deformation: the titanium-based piston rod part is subjected to tensile deformation treatment, the tensile strain rate is 0.5 mm / min, the maximum tensile deformation is 70% of the maximum fracture deformation, and it is maintained for 90 minutes, and ultrasonic vibration is continuously added during the tensile deformation treatment until the tensile deformation is completed, the vibration frequency is 40 kHz, and after the tensile deformation is completed and the force returns to zero, the titanium-based piston rod part is removed to obtain the titanium-based piston rod part after tissue deformation;

[0035] Step 2, organization control: the titanium-based piston rod part after organization deformation obtained in step 1 is placed in a heat treatment furnace for isothermal recovery at a temperature of 510°C and a heating rate of 10°C / min. After reaching the temperature, the part is kept at this temperature for 120 minutes. After the temperature is reached, the part is cooled to room temperature with the furnace to obtain the titanium-based piston rod part after organization control;

[0036] Step 3, ion nitriding: put the multiple titanium-based piston rod parts after tissue adjustment obtained in step 2 into the cathode disk of the DC pulse ion nitriding furnace with a spacing of more than 30 mm, and use titanium alloy tooling to raise it, turn on the vacuum pump to evacuate to below 10Pa, then introduce high-purity nitrogen, turn on the auxiliary heating and pulse power supply, and gradually increase the pulse voltage and duty cycle. After reaching the nitriding temperature, carry out insulation nitriding. The process parameters of insulation nitriding are: power frequency 2000Hz, duty cycle 75%, voltage 1000V, vacuum 1Torr, temperature 850℃. After the end, turn off the pulse power supply and auxiliary heating, cool to below 100℃ with the furnace and take it out to obtain a titanium-based piston rod part with a nitriding layer of 100μm thickness on the surface.

[0037] Figure 1Figure 2 is a metallographic structure diagram of the titanium-based piston rod part before and after the organization deformation regulation in Example 2 of the present invention, wherein Figure (a) is a metallographic structure diagram of the titanium-based piston rod part after the organization deformation regulation, and Figure (b) is a metallographic structure diagram of the titanium-based piston rod part before the organization deformation regulation. Figure 1 It can be seen that compared with the titanium-based piston rod parts without structural deformation control, the α phase inside the matrix of the titanium-based piston rod parts after structural deformation control in the present invention is broken, achieving the purpose of refining the structure, and more grain boundaries are significantly increased inside the matrix, providing more channels for the diffusion of nitrogen atoms.

[0038] Figure 2 The metallographic image of the nitriding layer prepared on the surface of the titanium-based piston rod part in this embodiment is shown in FIG. Figure 2 It can be seen that the nitrided layer is uniform and continuous, and the thickness of the nitrided layer is 100 μm.

[0039] Figure 3 The cross-sectional hardness gradient diagram of the nitrided layer prepared by the organization deformation regulation and the nitrided layer prepared without organization deformation regulation on the surface of the titanium-based piston rod part in Example 2 of the present invention is shown in FIG. Figure 3 It can be seen that compared with titanium-based piston rod parts that are directly nitrided without structural deformation control, the titanium-based piston rod parts after structural deformation and phase transformation recovery in the present invention can obtain a thicker nitriding hardened layer within the same process time.

[0040] Example 3

[0041] This embodiment includes the following steps:

[0042] Step 1, tissue deformation: the titanium-based piston rod part is subjected to tensile deformation treatment, the tensile strain rate is 0.5 mm / min, the maximum tensile deformation is 70% of the maximum fracture deformation, and it is maintained for 90 minutes, and ultrasonic vibration is continuously added during the tensile deformation treatment until the tensile deformation is completed, the vibration frequency is 40 kHz, and after the tensile deformation is completed and the force returns to zero, the titanium-based piston rod part is removed to obtain the titanium-based piston rod part after tissue deformation;

[0043] Step 2, organization control: the titanium-based piston rod part after organization deformation obtained in step 1 is placed in a heat treatment furnace for isothermal recovery at a temperature of 510°C and a heating rate of 8.0°C / min. After reaching the temperature, the part is kept at this temperature for 90 minutes. After the temperature is reached, the part is cooled to room temperature with the furnace to obtain the titanium-based piston rod part after organization control;

[0044] Step 3, ion nitriding: put the multiple titanium-based piston rod parts after tissue adjustment obtained in step 2 into the cathode disk of the DC pulse ion nitriding furnace with a spacing of more than 30 mm, and use titanium alloy tooling to raise it, turn on the vacuum pump to evacuate to below 10Pa, then introduce high-purity nitrogen, turn on the auxiliary heating and pulse power supply, and gradually increase the pulse voltage and duty cycle. After reaching the nitriding temperature, carry out heat-insulating nitriding. The process parameters of heat-insulating nitriding are: power frequency 2000Hz, duty cycle 50%, voltage 800V, vacuum 5Torr, temperature 850℃. After the end, turn off the pulse power supply and auxiliary heating, cool to below 100℃ with the furnace and take it out to obtain a titanium-based piston rod part with a nitriding layer of 60μm thickness on the surface.

[0045] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A surface strengthening method for a titanium-based piston rod part, characterized in that: The method comprises the following steps: Step 1: tissue deformation: the titanium-based piston rod part is subjected to a tensile deformation treatment to obtain a titanium-based piston rod part after tissue deformation; Step 2, tissue control: placing the titanium-based piston rod part after tissue deformation obtained in step 1 into a heat treatment furnace for isothermal recovery, and cooling it to room temperature with the furnace after the recovery to obtain a titanium-based piston rod part after tissue control; Step 3, ion nitriding: put the titanium-based piston rod parts after organization control obtained in step 2 into the cathode disk of the DC pulse ion nitriding furnace, turn on the vacuum pump to evacuate, then introduce the nitriding gas, turn on the auxiliary heating and pulse power supply, and gradually increase the pulse voltage and duty cycle. After reaching the nitriding temperature, carry out heat preservation nitriding. After the end, turn off the pulse power supply and auxiliary heating, cool with the furnace to below 100°C and take out to obtain a titanium-based piston rod part with a nitriding layer on the surface.

2. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: The maximum tensile deformation of the tensile deformation treatment in step 1 is 20% to 70% of the maximum fracture deformation of the titanium-based piston rod part, and is maintained for 30 minutes to 90 minutes.

3. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: During the stretching deformation treatment in step 1, ultrasonic vibration is continuously added until the stretching deformation is completed, and the vibration frequency is 10kHz to 40kHz. After the stretching deformation is completed and the force returns to zero, the titanium-based piston rod part is removed.

4. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: The temperature of the isothermal recovery in step 2 is 499°C to 510°C, the heating rate is 3.0°C / min to 10.0°C / min, and the temperature is kept for 60min to 120min after reaching the temperature.

5. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: The process parameters of the heat preservation nitriding in step 3 are: power frequency 1000Hz~2000Hz, duty cycle 10%~75%, voltage 300V~1000V, vacuum degree 1Torr~8Torr, temperature 700℃~850℃.

6. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: In step three, multiple titanium-based piston rod parts with regulated structures are placed in the cathode disk with a spacing of more than 30 mm, and are raised with titanium alloy tooling.

7. The surface strengthening method of a titanium-based piston rod part according to claim 1, characterized in that: The thickness of the nitriding layer in step three is 10 μm to 100 μm.

Images