• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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    • 专利摘要:
    The invention relates to a titanium alloy laser additive repair and surface nitriding composite treatment process. First of all, the surface of titanium alloy parts is pretreated, and the laser additive repair process parameters are as follows: The laser power is 1300-1500w, the scanning speed is 13mm/s, the spot diameter is 3.5-4mm, the powder feeding amount is 25-30g/min, the overlap amount is 50%, and the height direction increment Z is 0.3mm/1ayer, After the surface of the repaired titanium alloy is treated, the size and precision of the titanium alloy are restored, and then the titanium alloy is nitriding treated: Nitrogen pressure 200-500pa, temperature 540-650 °C, time 3-8h, duty cycle 80, The voltage is - 500V. Finally, it was annealed at 450 °C for 1 h. As a result, high quality titanium alloy repair and surface modification samples were obtained. The hardness of the surface modification layer of the repaired samples was as high as llOOHV-IZOOHV, and the wear resistance was 3-5 times higher than that of the substrate.
    公开号:NL2028331A
    申请号:NL2028331
    申请日:2021-05-28
    公开日:2021-08-23
    发明作者:Li Cong；Li Wei；Xiao Bin；Qiu Wei；Chen Jian；He Jianjun；Xie Pan
    申请人:Univ Changsha Science & Tech；
    IPC主号:
    专利说明:

    A Composite Treatment Process of Titanium Alloy Laser Additive Repair And Surface Nitriding Technical Field The invention relates to the field of laser metal material processing, in particular to a titanium alloy laser additive repair and surface nitriding composite treatment process.
    Technical Background Titanium and titanium alloys are widely used in the manufacture of key components in aerospace, nuclear industry and biomedical fields due to their low density, high specific strength, excellent corrosion resistance and high temperature resistance.
    However, titanium alloy parts have low surface hardness and poor wear resistance, and are very sensitive to adhesive wear and fretting wear.
    Titanium alloy parts are prone to wear, crack and fatigue during service, which lead to parts failure and economic losses.
    Using high-energy laser beam as heat source, laser additive repair technology has the characteristics of low heat input, small dilution, small heat-affected zone and small deformation, which can realize rapid remanufacturing of titanium alloy parts.
    In general, under the same service environment, titanium alloy repair parts are likely to be worn again in the later service process.
    Therefore, it is necessary to modify the surface of the repair area of titanium alloy parts.
    Titanium nitride has the advantages of high melting point, high hardness, excellent wear resistance and high temperature stability.
    Preparation of titanium nitride modified layer on the surface of titanium alloy parts is an effective method to improve the surface hardness, wear resistance, service life and application range of titanium alloy parts.
    At present, ion nitriding, laser gas nitriding and gas nitriding are mainly used to prepare nitride modified layer on the surface of titanium alloy steel.
    Ton nitriding is difficult to deal with complex parts and the cost is high.
    Laser nitriding is easy to produce defects, such as pores and cracks.
    Gas nitriding is more and more widely used because of its simplicity and low cost, which can form nitride hard phase on the surface of titanium alloy steel and significantly improve the wear resistance and corrosion performance.
    The invention provides a composite treatment process of titanium alloy laser repair and surface nitriding, which can improve the surface performance of the repair area while ensuring the quality of titanium alloy repair.
    Summary of the Invention The purpose of the invention is to provide a titanium alloy laser additive repair and surface nitriding composite treatment process.
    Step 1: Pre-treat the surface of titanium alloy parts, including machining, cleaning, sandblasting and drying of the area to be repaired; Step 2: The thermal imager was used to monitor the molten pool in the process of laser additive manufacturing to obtain the molten pool morphology and temperature change information, calculate the mean value of the long axis of the molten pool A and the mean value of the short axis of the molten pool B, and calculate the average cooling rate & of the molten pool boundary.
    Step 3: The process parameters were optimized according to the principle of 1.5S=a/S2.2 and 7.0X 103°C/sS&S8.3 XxX 104°C/s to obtain the optimized additive repair process window: The laser power is 1300-1500W, the scanning speed is 13mm/s, the spot diameter is 3.5-4mm, the powder feeding amount is 25-30g/min, the lap amount is 50%, and the height direction increment Z is 0.3mm/layer; Step 4: Repair the titanium alloy with the optimized process parameters, and conduct mechanical machining, polishing, sandblasting and cleaning on the surface of the titanium alloy after repair to restore the size and precision of the titanium alloy; Step 5: Put the repaired titanium alloy in the nitriding furnace for nitriding treatment: nitrogen pressure is 200-500Pa, nitriding temperature is 540-650°C, nitriding time is 3-8 hours, duty cycle is 80; The voltage is -500V; Step 6: Subsequent treatment of titanium alloy repair and modification: annealing temperature 450°C, annealing time 1h.
    In the Step 2, the emissivity of the thermal imager was set to 1.0 and the individual data acquisition time was 1.5ms.
    In Step 4, the repair material is a mixture of titanium alloy powder, pure zirconium powder and pure aluminum powder, including 98% titanium alloy powder by mass fraction, 1.5% pure chromium powder and 0.5% pure aluminum powder; The filling path is the cross-scanning path; In Step 5, the heating conditions are as follows: when the vacuum degree of the vacuum chamber in the nitriding furnace is less than 110-4 Pa, nitrogen is introduced, The titanium alloy comprises « titanium alloy, a +8 titanium alloy and B titanium alloy.
    Through strict screening and optimization of the laser additive repair process, the optimized repair process parameters are obtained as follows: The laser power is 1300-1500W, the scanning speed is 13mm/s, the spot diameter is 3.5-4mm, the powder feeding amount is 25-30g/min, the lap amount is 50%, and the height direction increment Z is 0.3mm/layer; According to the above process parameters and methods, the laser additive repair, on the one hand, can ensure sufficient laser energy input and molten pool cooling rate in the repair process, avoid metallurgical defects and fine dendrite structure; On the other hand, a small amount of pure zirconium powder and pure aluminum powder are added to the repair powder.
    In the process of additive repair, pure zirconium powder and pure aluminum powder react in situ with oxygen in the molten pool to produce high melting point zirconia and alumina ceramic particles.
    These high melting point particles provide heterogeneous nucleation points for the nucleation of grains or dendrites during the solidification process of molten pool, and then refine the grains.
    In addition, through the optimization of nitriding process, the optimized nitriding process parameters are obtained as follows: Nitrogen pressure is 200-500Pa, nitriding temperature is 540-650°C, nitriding time is 3-8 hours, duty cycle is 80; The voltage is -500V; Then, the repaired and nitrided samples were subjected to subsequent treatment at 450°C and Ih.
    By nitriding the repaired parts according to the above process parameters and methods, a controllable and high-performance nitriding layer can be obtained on the surface of repaired parts.
    It is worth mentioning that the titanium alloy repair parts obtained by the method of the present invention have refined grain structure, which can provide more diffusion channels (grain boundaries) for subsequent nitriding treatment, promote the nitriding reaction, and form a nitriding layer with uniform thickness, high hardness and high wear resistance on the surface of the titanium alloy repair parts.
    High quality repair and surface modification samples can be obtained by using the method of the invention.
    The titanium alloy repair parts have no metallurgical defects inside and fine microstructure.
    The surface modification layer hardness of the repair parts is as high as 1100HV-1200HV, and the wear resistance of the repair parts is 3-5 times higher than that of the base material.
    Descriptions of the Drawings Fig. 1 is the metallographic diagram of titanium alloy repair samples obtained by existing methods.
    Fig. 2 is the metallographic diagram of titanium alloy additive repair and modified sample obtained by the invention.
    Detailed Description of the Preferred Embodiments Embodiment 1 Taking TC4 as an example ( a + 8 Two phase) alloy.
    Step 1: Pre-treat the surface of TC4 alloy parts, including machining, cleaning, sandblasting and drying of the area to be repaired; Step 2: The thermal imager was used to monitor the molten pool in the process of laser additive manufacturing to obtain the molten pool morphology and temperature change information, calculate the long axis mean value of the molten pool A and short axis mean value of the molten pool B, and calculate the average cooling rate & of the molten pool boundary; Step 3: The process parameters were optimized according to the principle of 15S=a/bS2.2 and 7.0X 103°C/s&&S8.3 X 104°C/s to obtain the optimized additive repair process window: The laser power is 1300-1500W, the scanning speed is 13mm/s, the spot diameter is 3.5-4mm, the powder feeding amount is 25-30g/min, the lap amount is 50%, and the height direction increment Z is 0.3mm/layer; Step 4: Repair the titanium alloy with the optimized process parameters, and conduct mechanical machining, polishing, sandblasting and cleaning on the surface of the titanium alloy after repair to restore the size and precision of the titanium alloy; Step 5: Put the repaired titanium alloy in the nitriding furnace for nitriding treatment: nitrogen pressure is 200-500Pa, nitriding temperature is 540-650°C, nitriding time is 3-8 hours, duty cycle is 80; The voltage is -500V, Step 6: Subsequent treatment of titanium alloy repair and modification: annealing temperature 450°C, annealing time 1h. High-quality repair and surface modification samples were obtained. TC4 titanium alloy repair parts had no metallurgical defects and fine microstructure. The surface modification layer hardness of the repair parts was as high as 1120HV, and the wear resistance of the repair parts was 4.5 times higher than that of the substrate.
    Fig. 1 shows the metallographic diagram of titanium alloy repair samples obtained by the existing methods. The internal structure of the titanium alloy repaired sample is relatively dense, without obvious metallurgical defects such as cracks and pores, and the average hardness of the repaired area is about 356HV. The above results indicate that it 1s difficult to obtain titanium alloy repair samples with high hardness other than the method of the present invention.
    Fig. 2 is the metallographic diagram of the titanium alloy repair and modification sample obtained by embodiment 1 of the present invention. The microstructure of titanium alloy repaired samples 1s compact, and there are no metallurgical defects such as pores and cracks. The average hardness of repaired area is 403hv; There is an obvious nitriding layer on the surface of the repaired sample, and the surface hardness is up to 1120hv. It can be seen that the wear resistance of titanium alloy repaired sample surface can be effectively improved by adopting the method of the invention. The method proposed in the invention not only strictly controls the temperature of the molten pool to ensure the high-dense titanium alloy repair sample, but also strictly controls the nitriding process parameters to ensure the nitriding under the condition of low nitrogen potential, so as to improve the quality and hardness of the nitriding layer. The above results show that the method can effectively improve the surface properties of titanium alloy repaired samples.
    Embodiment 2 Taking TB I( B -type) alloy as an example.
    Step 1: The surface of tbl titanium alloy parts was pretreated, including machining, 5 cleaning, sandblasting and drying; Step 2: the thermal imager is used to monitor the molten pool in the laser additive manufacturing process, obtain the molten pool morphology and temperature change information, calculate the average value of long axis A and short axis B of molten pool, and calculate the average cooling rate & of molten pool boundary; Step 3: Optimize the process parameters according to the principle of 1.5<Xa/b<<2.2 and 7.0X 10°" C/s<<E<KR3 X10 C/s to obtain the optimized additive repair process window: The laser power is 1450W, the scanning speed is 13mm/s, the spot diameter 1s 3.5mm, the powder feeding amount is 27g/min, the lap amount is 50%, the height direction increment Z is 0.3mm/layer, the repair material is a mixture of TB1 titanium alloy powder, pure zirconium powder and pure aluminum powder, including the mass fraction of TB1 titanium alloy powder is 98%, 1.5% pure chrome powder and 0.5% pure aluminum powder, the filling path is the cross scanning path; Step 4: Repair the TBI titanium alloy parts with the above optimized process parameters, and conduct mechanical machining, polishing, sandblasting and cleaning on the surface of the titanium alloy after repair to restore the size and precision of the titanium alloy; Step 5: Put the repaired titanium alloy parts in the nitriding furnace for nitriding treatment: when the vacuum degree of the vacuum chamber in the nitriding furnace is less than 110-4 Pa, nitrogen is passed into the furnace, nitrogen pressure is 200-500Pa, nitriding temperature is 540-650°C, nitriding time is 3-8 hours, duty cycle is 80; The voltage is -500V; Step 6: Subfollow-up treatment of titanium alloy repair and modification: annealing temperature 450°C, annealing time Ih, obtain high quality repair and surface modification samples, TB1 titanium alloy repair parts have no metallurgical defects inside, and the microstructure is fine, the surface modification layer hardness of the repair parts is as high as 1180HYV, wear resistance is 4 times higher than that of the base material.
    权利要求:
    Claims (6)
    [1]
    1. A method of repairing a titanium alloy laser consumable and nitriding and composite treating a surface thereof, comprising the following steps: Step 1: Surface preparation of a titanium alloy part, including machining, cleaning, sandblasting and drying a region to be repaired; Step 2: Using a thermal imager to monitor a weld pool during the manufacturing process of the laser-added material to obtain information about shape and temperature change of the weld pool, the mean value a along the long axis and the mean value b over the calculate the short axis of the molten bath, and calculate the average cooling rate & of a boundary of the molten bath step 3: according to the principle of 1.5<a/b<2.2 and 7.0x103°C/s<£<8, 3x104°C/s, optimizing process parameters to obtain an optimized addition material repair process window, in which laser power is 1300-1500 W, a scanning speed is 13 mm/s, a dot diameter is 3.5-4 mm, a powder feeding rate is 25-30g/min, overlapping amount is 50%, and height direction increment Z is 0.3mm/low; step 4: use the optimized process parameters to repair a titanium alloy and perform mechanical processing, polishing, sandblasting and cleaning on the surface of the repaired titanium alloy to restore the size and accuracy of the titanium alloy; step 5: placing the repaired titanium alloy in a nitriding furnace for nitriding treatment, in which a nitrogen pressure of 200-500 Pa, a nitriding temperature of 540-650 °C, a nitriding time of 3-8 hours, a duty cycle of 80 and a voltage of -500 V is applied; step 6: post-treatment of the repair and modification of titanium alloys, whereby the annealing temperature is 450°C and the annealing time is 1 hour.
    [2]
    2. The method of repairing the titanium alloy laser addition material and nitriding and compound treatment of the surface thereof according to claim 1, wherein in step 2, the emissivity of the thermal imager is set to 1.0, and single data collection time is 1, 5 ms.
    [3]
    3. The method of repairing the titanium alloy laser addition material and nitriding and compound treatment of the surface thereof according to claim 1, where in step 4, the repair material is a mixture powder of a titanium alloy powder, a pure zirconium powder and a pure aluminum powder, including titanium alloy powder of mass fraction of 98%, pure chromium powder of mass fraction of 1.5%, and pure aluminum powder of mass fraction of 0.5%.
    [4]
    4. The method of repairing the titanium alloy Laser Addition Material and nitriding and compositionally treating the surface thereof according to claim 1, wherein in step 4, a filling path is a cross scan path.
    [5]
    5. The method of repairing the laser-added titanium alloy material and nitriding and compounding the surface thereof according to Claim 1, where in Step 5, a heating condition is as follows: when the vacuum degree of the vacuum chamber in the nitriding furnace is less than 110-4 Pa, nitrogen is introduced. X
    [6]
    6. The method for recovering the titanium alloy laser additive material and nitriding and compound treatment of the surface thereof according to claim 1, wherein the titanium alloy is as follows: a titanium alloy, a + B titanium alloy, or B titanium alloy.
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CN202011536999.3A|CN112548103B|2020-12-23|2020-12-23|Titanium alloy laser additive repair and surface nitriding composite treatment process|
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