Vacuum pump surface melting plating process

Abstract

The invention belongs to the technical field of surface engineering treatment, and particularly relates to a vacuum pump surface melting plating process. The vacuum pump surface melting plating process comprises the steps of activating treatment, vacuum melting plating, heat treatment, machining and the like. The surface of the vacuum pump is activated through sand blasting activation and acid pickling activation, and the bonding strength of the vacuum pump and a plating layer is effectively improved; the vacuum pump is subjected to preheating treatment before melt plating, and laser melt plating is carried out by adopting high laser intensity and high scanning speed, so that a prepared plating layer has high hardness and good wear resistance; by improving the formula of the alloy powder and controlling the dosage of the components in the formula, the wear resistance and impact resistance of the coating are further improved; the vacuum pump subjected to melt plating is subjected to segmented heat treatment, so that heat stress in a plating layer of the vacuum pump is effectively eliminated, and the phenomenon of cracks or falling of the plating layer caused by stress concentration is effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface engineering treatment, and particularly relates to a surface melting plating process for a vacuum pump. Background Art

[0002] A vacuum pump can reduce the system pressure by pumping out the gas or vapor in the system, creating the required vacuum environment, so as to realize various operations in the chemical production process, ensure the product quality and production efficiency, and is applied in the fields of industrial manufacturing, scientific research, medical treatment, aerospace, etc., continuously promoting the technological progress and efficiency improvement of various industries.

[0003] With the continuous development and progress of the chemical industry, the requirements for vacuum pumps are also getting higher and higher. The pump shell, seal liquid disc, and pump cover of the vacuum pump are all made of gray cast iron. Gray cast iron is convenient for casting parts with complex structures, but the strength of cast iron is relatively low and the corrosion resistance is poor. In order to improve the performance and service life of the vacuum pump, a coating process needs to be carried out on the surface of the vacuum pump. Common coating methods include physical vapor deposition, chemical vapor deposition, electroplating, melting plating, etc. Among them, the melting plating process has the characteristics of being applicable to substrate materials of various shapes and sizes and having relatively low requirements for substrate materials, and has become the mainstream process for vacuum pump coating. The melting plating process heats the coating material to a liquid state through a high-temperature heat source, and uses the fluidity and wettability of the liquid metal to evenly cover the surface of the substrate under the action of gravity, centrifugal force, pressure, etc. As the liquid metal rapidly cools and solidifies, a firm bonding layer is formed with the substrate, so as to achieve the purpose of improving the surface performance of the substrate. Common melting plating processes include hot dip plating, spray fusing plating, surfacing melting plating, and laser cladding process. However, the preparation costs of the hot dip plating process and the thermal spraying process are relatively high, which limits the large-scale engineering application and promotion. The process parameters and operation technical requirements of the surfacing melting plating are relatively high, and there may be incomplete fusion phenomena between the surfacing layer and the substrate or between the surfacing layers, affecting the performance of the coating material. The cooling speed of the laser cladding process is fast, which can form a fine-grained structure inside the material, and the dilution rate is low. The melting coating layer and the substrate are firmly metallurgically bonded or interfacially diffusion bonded. However, the common laser cladding process has a relatively high heat input to the vacuum pump, which is easy to form relatively large residual stresses, resulting in cracks in the melting coating layer, affecting the microstructure and performance of the melting coating layer, and affecting its service life.

[0004] The Chinese patent application document with the publication number CN107130240A discloses a laser cladding method, including: covering the metal substrate to be processed with the protective cover; introducing an inert gas through the first air inlet on the outer layer to make the space covered by the protective cover filled with the inert gas; introducing a coolant into the second cavity through the first liquid inlet and discharging the coolant in the second cavity through the first liquid outlet to continuously provide a cold source; introducing metal powder into the powder feeding channel to make the metal powder converge on the surface of the metal substrate; starting the laser to make the laser beam generated by the laser melt the metal powder converged on the surface of the metal substrate and the surface of the metal substrate to form a molten pool, and after cooling, a cladding layer is formed on the surface of the metal substrate. However, in this method, the temperature difference between the cladding layer and the substrate is relatively large, and the performance difference between the cladding layer and the substrate material is also relatively large. Stress concentration will be caused at the bonding interface due to technical problems such as the solidification of the cladding metal and the material performance difference. When bearing a load, fatigue is likely to occur at the stress concentration point in the coating, resulting in the peeling off of the coating, affecting the appearance and corrosion resistance and other properties of the coating. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, such as large stress in the vacuum pump cladding layer, weak bonding with the substrate, easy peeling off, and easy generation of microcracks or peeling off, the present invention provides a surface cladding process for a vacuum pump.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A surface cladding process for a vacuum pump includes the following steps: S1: Activate the surface of the vacuum pump to obtain a standby vacuum pump; S2: Preheat the standby vacuum pump prepared in step S1 to 100 - 120 °C, keep it warm for 1 - 1.5 h, then add alloy powder into the spray gun and continuously feed the powder onto the surface of the vacuum pump aligned with the laser head through a laser coaxial powder feeding system, and scan the surface of the vacuum pump with the alloy powder attached by the laser to form a cladding layer. During the cladding process, use an inert gas to protect the cladding part to obtain a cladded vacuum pump; S3: Perform segmented heat treatment on the cladded vacuum pump prepared in step S2 to obtain a heat-treated vacuum pump; S4: Perform machining on the heat-treated vacuum pump prepared in step S3 to remove the excess surface layer; The alloy powder includes Cr, Ti, Si, HBN, C, Ni.

[0007] In the above technical solution, heating the standby vacuum pump to 100-120°C in step S2 can effectively remove the moisture on the surface of the standby vacuum pump, improve the bonding force between the alloy powder and the substrate. At the same time, within this temperature range, the dilution rate of the cladding layer is relatively low, and the temperature difference with the molten pool is relatively large, and the cooling rate of the cladding layer is relatively large, which is conducive to refining the grain structure of the cladding layer and achieving the effect of fine grain strengthening.

[0008] Cr in the alloy powder can cause solid solution strengthening of the Ni substrate, enhancing the corrosion resistance of the Ni-based alloy. At the same time, Cr can also react with C to form Cr7C3, which is dispersed in the Ni-based alloy substrate, playing a role of dispersion strengthening, thereby greatly improving the wear resistance of the alloy cladding layer. Si can form eutectics with Ni and Fe, significantly reducing the melting point of the alloy. Moreover, it is a strong oxygenophilic element that can reduce the oxides on the metal surface, generate SiO2, form borosilicate glass with other metal oxides, and has good fluidity. It is easy to float in the liquid alloy and cover the surface of the molten metal, avoiding the oxidation of the liquid alloy. In addition, Si can form a Si-Ni solid solution in the austenite of Ni, producing solid solution strengthening, thereby improving the strength of the alloy. HBN (hexagonal boron nitride) has good lubricity and chemical stability, can effectively reduce the sintering temperature of the alloy powder, and its dispersion in the Ni alloy substrate can effectively hinder the movement of dislocations, making it difficult for the alloy coating to deform when stressed, thereby improving the wear resistance of the alloy coating. Performing segmented heat treatment on the cladding vacuum pump can effectively remove the thermal stress in the cladding layer, avoid cracks and peeling caused by stress concentration in the coating, and extend the service life of the vacuum pump.

[0009] Further, the activation treatment in step S1 includes sandblasting activation and pickling activation. The sandblasting activation uses iron sand, and the pickling activation uses a phosphoric acid solution.

[0010] In the above technical solution, the sandblasting activation uses iron sand with a relatively large density, which can form deeper pits on the surface of the vacuum pump during the activation treatment, thereby improving the adhesion of the coating on the surface of the vacuum pump and preventing it from falling off; pickling activation is to use a phosphoric acid solution to chemically react with the oxides on the surface of the vacuum pump and dissolve them, while making the surface of the vacuum pump present an active state. The phosphating film on the surface of the vacuum pump after pickling helps to improve the adhesion of the coating.

[0011] Even further, the activation treatment in step S1 is specifically: selecting iron sand with a particle size of 40-50 mesh to perform sandblasting treatment on the vacuum pump, with a sandblasting pressure of 0.5-0.7 MPa and a treatment time of 20-30 min. After cleaning, place the vacuum pump in a phosphoric acid solution with a concentration of 1.5-2.3 mol / L, heat it to 50-60°C and treat it for 20-30 min, then fish it out and wash it with water until the washing liquid is neutral.

[0012] Further, the powder output of the spray gun described in step S2 is 35 - 40 g / min, and the powder supply pressure is 0.7 - 0.9 MPa.

[0013] Further, the weight percentages of the components in the alloy powder are as follows: Cr 12.31% - 12.76%, Ti 24.25% - 25.10%, Si 0.07% - 0.12%, HBN 0.04% - 0.09%, C 0.12% - 0.16%, and the balance is Ni.

[0014] In the above technical solution, the higher the Si and C contents in the alloy powder, the better the hardness and wear resistance of the alloy powder. However, when the Si and C contents exceed the range limited by the present invention, more brittle silicon oxides and silicate compounds will appear at the grain boundaries of the alloy coating, reducing the toughness of the alloy coating, and cracks or even peeling may occur when subjected to external forces.

[0015] Furthermore, the weight percentages of the components in the alloy powder are as follows: Cr 12.57%, Ti 24.85%, Si 0.09%, HBN 0.07%, C 0.15%, and the balance is Ni.

[0016] Further, the particle size of the alloy powder is 45 - 55 μm.

[0017] Further, in step S2, the laser power of the laser is 4.5 - 5.0 kW, the beam spot diameter is 3 mm, the scanning speed is 13 - 15 mm / s, and the gas flow rate of the inert gas is 20 - 23 L / min.

[0018] In the above technical solution, the power and scanning speed of the laser will affect the structure and properties of the molten coating. It is found that within the range of the laser power and scanning speed provided by the present invention, the structure of the molten coating becomes finer, the surface stress is reduced, the number of cracks is decreased, and the content of the amorphous phase in the molten coating increases, significantly improving the fiber hardness and wear resistance. This is because a higher laser power can rapidly heat up and then rapidly cool the alloy powder, resulting in a higher and more gentle temperature gradient in the molten pool, effectively reducing the stress concentration phenomenon, accelerating atomic diffusion, facilitating the formation of more crystal nuclei, and reducing the formation of microcracks; while too fast a scanning speed shortens the residence time of the molten pool, reduces the heat accumulation inside the molten pool, increases the degree of undercooling in the molten pool, is conducive to the formation of crystal nuclei, and plays a role in refining the grains.

[0019] Further, in step S2, the thickness of the molten coating is 1.2 - 1.5 mm.

[0020] Further, the specific steps of the segmented heat treatment in step S3 are as follows: Heat the melting plating vacuum pump to 500 - 530 °C, keep it warm for 4 - 4.5 h, after cooling, continue to heat it to 320 - 330 °C, keep it warm for 3.4 - 4 h, and then cool it down.

[0021] Through the above technical solution, the melting plating vacuum pump is heated to 500 - 530 °C, and the atoms in the substrate and the coating further diffuse. The residual stress in the coating is effectively released through the rearrangement of atoms, improving the bonding strength between the coating and the substrate. Keeping it warm for 4 - 4.5 h can effectively promote recrystallization and grain refinement inside the coating, making the microstructure of the coating more uniform; after cooling, it is heated to 320 - 330 °C again. Within this temperature range, the thermal stress in the coating can be further released, further playing the role of fine grain strengthening and improving the wear resistance of the coating.

[0022] Compared with the prior art, a vacuum pump surface melting plating process provided by the present invention has the following technical advantages: (1) The present invention activates the surface of the vacuum pump through sandblasting activation and pickling activation, effectively improving the bonding strength between the vacuum pump and the coating; (2) The present invention preheats the vacuum pump before melting plating and uses a relatively high laser intensity and a relatively fast scanning speed for laser melting plating, making the obtained coating have a relatively high hardness and good wear resistance; (3) The present invention improves the formula of the alloy powder and controls the dosage of the formula components, making the obtained coating have good corrosion resistance, wear resistance and impact resistance; (4) The present invention conducts segmented heat treatment on the vacuum pump after melting plating, effectively eliminating the thermal stress in the vacuum pump coating and effectively avoiding the cracking or peeling phenomenon of the coating caused by stress concentration. Description of the Drawings

[0023] Figure 1 It is the scanning electron microscope picture of the coating obtained in Example 1; Figure 2 It is the scanning electron microscope picture of the coating obtained in Example 2; Figure 3 It is the scanning electron microscope picture of the coating obtained in Example 3. Specific Embodiments

[0024] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art can make various modifications according to the basic idea of the present invention, but as long as they do not depart from the basic idea of the present invention, they are within the scope of the present invention.

[0025] In this specific embodiment, the laser used is an LDM 6000-100 semiconductor laser, and the energy distribution of the laser spot is relatively uniform. The diameter of the laser spot is 3 mm, and a HINO50W coaxial annular high-speed powder feeding nozzle is used, and the diameter of the powder converging spot is not more than 1.5 mm. A PF2-2 double-barrel synchronous powder feeder is used, and argon is used as the powder feeding gas.

[0026] In this specific embodiment, to facilitate the detection of the fusion coating, gray cast iron sheets of the same material as the vacuum pump are used to replace the vacuum pump for the surface fusion coating process. The size of the gray cast iron sheet is 10 mm × 10 mm × 5 mm, and the chemical composition of the gray cast iron sheet is: C 2.8%, Si 1.5%, Mn 1.0%, P 0.08%, S 0.05%, and the balance is Fe.

[0027] Example 1 A surface fusion coating process for a vacuum pump includes the following steps: S1: Activate the surface of the vacuum pump to obtain a standby vacuum pump; the specific activation treatment is: select iron sand with a particle size of 40 mesh to perform sandblasting on the vacuum pump, the sandblasting pressure is 0.5 MPa, the treatment time is 30 min, after cleaning, place the vacuum pump in a phosphoric acid solution with a concentration of 1.5 mol / L, heat it to 50 °C and treat it for 30 min, then take it out and wash it with water until the washing liquid is neutral; S2: Preheat the standby vacuum pump obtained in step S1 to 100 °C and keep it warm for 1.5 h. Then add alloy powder with a particle size of 45 μm to the spray gun and continuously feed the powder to the surface of the vacuum pump aligned with the laser head through the laser coaxial powder feeding system. The powder output of the spray gun is 35 g / min, and the powder feeding pressure is 0.7 MPa; scan the surface of the vacuum pump with the alloy powder attached by the laser, and form a fusion coating with a thickness of 1.2 mm. During the fusion coating process, an inert gas is used to protect the fusion coating part to obtain a fusion-coated vacuum pump; the laser power of the laser is 4.5 kW, the beam diameter is 3 mm, the scanning speed is 13 mm / s, and the gas flow rate of the inert gas is 20 L / min; S3: Heat the fusion-coated vacuum pump obtained in step S2 to 500 °C, keep it warm for 4.5 h, cool it and then heat it to 320 °C, keep it warm for 4 h, and then cool it to obtain a heat-treated vacuum pump; S4: Machine the heat-treated vacuum pump obtained in step S3 to remove the excess surface layer; The alloy powder includes the following components by weight percentage: Cr 12.31%, Ti 24.25%, Si 0.07%, HBN 0.04%, C 0.12%, and the balance is Ni.

[0028] Example 2 A surface fusion coating process for a vacuum pump includes the following steps: S1: Activate the surface of the vacuum pump to obtain a standby vacuum pump. The activation treatment is specifically as follows: Select iron sand with a particle size of 50 mesh to perform sandblasting on the vacuum pump. The sandblasting pressure is 0.7 MPa, and the treatment time is 20 min. After cleaning, place the vacuum pump in a phosphoric acid solution with a concentration of 2.3 mol / L, heat it to 60 °C and treat for 20 min. After fishing out, wash it with water until the washing liquid is neutral. S2: Preheat the standby vacuum pump prepared in step S1 to 120 °C and keep it warm for 1.5 h. Then add alloy powder with a particle size of 55 μm into the spray gun and continuously feed the powder to the surface of the vacuum pump aligned with the laser head through the laser coaxial powder feeding system. The powder output of the spray gun is 40 g / min, and the powder feeding pressure is 0.9 MPa. Use the laser to scan the surface of the vacuum pump with the alloy powder attached to form a molten coating with a thickness of 1.5 mm. During the melting process, use inert gas to protect the melting part to obtain a melted vacuum pump. The laser power of the laser is 5.0 kW, the beam diameter is 3 mm, the scanning speed is 15 mm / s, and the gas flow rate of the inert gas is 23 L / min. S3: Heat the melted vacuum pump prepared in step S2 to 530 °C, keep it warm for 4 h, cool it, and then continue to heat it to 330 °C, keep it warm for 3.4 h, and then cool it to obtain a heat-treated vacuum pump. S4: Perform machining on the heat-treated vacuum pump prepared in step S3 to remove the excess surface layer. The alloy powder includes the following components by weight percentage: Cr 12.76%, Ti 25.10%, Si 0.12%, HBN 0.09%, C 0.16%, and the balance is Ni.

[0029] Example 3 A surface melting process for a vacuum pump includes the following steps: S1: Activate the surface of the vacuum pump to obtain a standby vacuum pump. The activation treatment is specifically as follows: Select iron sand with a particle size of 45 mesh to perform sandblasting on the vacuum pump. The sandblasting pressure is 0.6 MPa, and the treatment time is 25 min. After cleaning, place the vacuum pump in a phosphoric acid solution with a concentration of 1.8 mol / L, heat it to 55 °C and treat for 26 min. After fishing out, wash it with water until the washing liquid is neutral. S2: Preheat the standby vacuum pump prepared in step S1 to 115 °C, keep it warm for 1.2 h, then add alloy powder with a particle size of 50 μm into the spray gun and continuously feed the powder onto the surface of the vacuum pump aligned with the laser head through a laser coaxial powder feeding system. The powder output of the spray gun is 38 g / min, and the powder feeding pressure is 0.8 MPa; Scan the surface of the vacuum pump with the alloy powder attached by the laser, forming a melting coating with a thickness of 1.4 mm. During the melting plating process, an inert gas is used to protect the melting plating area to obtain a melting-plated vacuum pump; The laser power of the laser is 4.8 kW, the beam spot diameter is 3 mm, the scanning speed is 14 mm / s, and the gas flow rate of the inert gas is 22 L / min; S3: Heat the melting-plated vacuum pump prepared in step S2 to 525 °C, keep it warm for 4.2 h, cool it, then continue to heat it to 325 °C, keep it warm for 3.6 h, and then cool it to obtain a heat-treated vacuum pump; S4: Machine the heat-treated vacuum pump prepared in step S3 to remove the excess surface layer; The weight percentages of the components in the alloy powder are as follows: Cr 12.57%, Ti 24.85%, Si 0.09%, HBN 0.07%, C 0.15%, and the balance is Ni.

[0030] Comparative Example 1 The surface melting plating process of the vacuum pump in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the preheating temperature in step S2 of this comparative example is 300 °C.

[0031] Comparative Example 2 The surface melting plating process of the vacuum pump in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in step S2 of this comparative example, the alloy powder uses an equal amount of Ni to replace HBN.

[0032] Comparative Example 3 The surface melting plating process of the vacuum pump in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in step S2 of this comparative example, the alloy powder uses an equal amount of Ni to replace Si.

[0033] Comparative Example 4 The surface melting plating process of the vacuum pump in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in step S2 of this comparative example, the alloy powder uses an equal amount of Ni to replace C.

[0034] Comparative Example 5 The surface melting plating process of the vacuum pump in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the laser power of the laser in step S2 of this comparative example is 3.0 kW.

[0035] Comparative Example 6 The surface melting plating process of the vacuum pump described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the scanning speed in step S2 of this comparative example is 7 mm / s.

[0036] Comparative Example 7 The surface melting plating process of the vacuum pump described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the specific steps of heat treatment in step S3 of this comparative example are: heating the melted-plated vacuum pump to 325 °C and holding for 7.8 h.

[0037] Test Example Test samples: Gray cast iron sheets of vacuum pumps prepared in Examples 1 - 3 and Comparative Examples 1 - 7; Hardness test: Refer to GB / T 230.1 - 2018 "Metallic materials - Rockwell hardness test" to conduct Rockwell hardness tests on the test samples. Measure 3 points at different positions for each specimen and calculate the average value; Impact resistance performance: Refer to GB / T 229 - 2020 "Metallic materials - Charpy pendulum impact test method" to conduct impact resistance performance tests on the test samples; Wear resistance test: Use an RTEC MFT - 5000 friction and wear testing machine to conduct friction and wear test. The applied load is 30 N, the sliding speed is 0.06 m / s, the wear time is 20 min, and the friction counter - part is a high - carbon steel ball with a diameter of 6 mm. Use an OLS - 4100 laser confocal microscope to measure the width and depth of the wear scar to calculate the wear volume. The calculation formula for the wear rate W is W = V / LS, where: V is the wear volume (mm 3 ), L is the applied load (N), and S is the sliding displacement (m); Residual stress test: Use a Stress - X residual stress measuring instrument to measure the residual stress on the surface of the cladding layer. The X - ray anode tube uses Cr - target Kα rays, and the 2θ diffraction angle is 128°.

[0038] The test results are shown in Table 1.

[0039] Table 1 Performance test results

[0040] As can be seen from Table 1, the hardness of the gray cast iron steel sheet coating prepared by using the surface melting plating process of the vacuum pump provided by the present invention is 46 - 51, the impact toughness is 712.7 - 721.3 kJ / m 2 , and the wear rate is 2.95 - 3.41 mm 3 / (N·m), the residual stress of the coating is 33.5 - 35.2 MPa, which fully demonstrates that the coating prepared by using the surface melting and plating process of the vacuum pump provided by the present invention has high hardness, good wear resistance and impact resistance, and the residual stress in the coating layer is low, which can effectively avoid cracking or peeling caused by stress concentration.

[0041] Compared with Example 3, in Comparative Example 1, the preheating temperature was increased in step S2, but the hardness of the prepared coating decreased, the impact toughness decreased, and the wear rate increased. This is because the high preheating temperature led to a decrease in the cooling rate of the molten coating crystals, and the growth of grains resulted in thick dendritic crystals, leading to a decrease in the hardness and toughness of the coating; in Comparative Example 2, the alloy powder in step S2 used an equal amount of Ni to replace HBN, but the wear rate of the prepared coating increased, which indicates that HBN can effectively improve the wear resistance of the coating; in Comparative Example 3, the alloy powder in step S2 used an equal amount of Ni to replace Si, and in Comparative Example 4, the alloy powder in step S2 used an equal amount of Ni to replace C, but the hardness and impact resistance of the prepared coating decreased, and the wear rate increased. This indicates that the addition of Si and C can form a solid solution and be dispersed in the coating, effectively improving the strength and wear resistance of the coating; in Comparative Example 5, the laser power of the laser was reduced in step S2, and in Comparative Example 6, the scanning speed was reduced in step S2, but the hardness and impact resistance of the prepared coating decreased, and the wear rate increased. This indicates that higher laser power and scanning speed are beneficial to the formation of crystal nuclei and play a role in fine grain strengthening; in Comparative Example 7, only low-temperature heat treatment was carried out in step S3, but the impact strength of the prepared coating decreased and the residual stress increased. This indicates that heat treatment at 500 - 530 °C for 4 - 4.5 h in the present invention can effectively release the residual stress in the coating and improve the bonding strength between the coating and the substrate.

[0042] In addition, the present invention also carried out scanning electron microscope tests on the coatings of the gray cast iron sheets of the vacuum pump prepared in Examples 1 - 3, and the test results are shown in Figures 1 - 3 . From Figures 1 - 3 it can be seen that no defects such as pores, cracks, and powder inclusions appeared in the coatings prepared by using the vacuum pump melting and plating process provided by the present invention, which indicates that the coating microstructure prepared by using the vacuum pump melting and plating process provided by the present invention is good and the melting and plating quality is high.

[0043] The above embodiments are only illustrative of the present invention and do not limit the present invention. Those skilled in the art shall not modify the above embodiments without departing from the spirit and scope of the present invention. All equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the technical idea of the present invention still fall within the protection scope of the present invention.

Claims

1. A surface melting and plating process for a vacuum pump, characterized in that, It includes the following steps: S1: Activate the surface of the vacuum pump to obtain a standby vacuum pump; S2: Preheat the standby vacuum pump obtained in step S1 to 100 - 120 °C, keep it warm for 1 - 1.5 h, then add the alloy powder into the spray gun and continuously feed the powder onto the surface of the vacuum pump aligned with the laser head through the laser coaxial powder feeding system, scan the surface of the vacuum pump with the alloy powder attached by the laser, form a molten coating, and use an inert gas to protect the molten coating part during the melting process to obtain a melt-plated vacuum pump; S3: Perform segmented heat treatment on the melt-plated vacuum pump obtained in step S2 to obtain a heat-treated vacuum pump; S4: Perform machining on the heat-treated vacuum pump obtained in step S3 to remove the excess surface layer; The alloy powder includes Cr, Ti, Si, HBN, C, and Ni.

2. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that, The activation treatment in step S1 includes sandblasting activation and pickling activation. The sandblasting activation uses iron sand, and the pickling activation uses a phosphoric acid solution.

3. The surface melting and plating process of the vacuum pump according to claim 2, wherein The activation treatment in step S1 is specifically: Select iron sand with a particle size of 40 - 50 mesh to perform sandblasting on the vacuum pump, the sandblasting pressure is 0.5 - 0.7 MPa, the treatment time is 20 - 30 min, after cleaning, place the vacuum pump in a phosphoric acid solution with a concentration of 1.5 - 2.3 mol / L, heat it to 50 - 60 °C and treat it for 20 - 30 min, then take it out and wash it with water until the washing liquid is neutral.

4. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that In step S2, the powder output of the spray gun is 35 - 40 g / min, and the powder supply pressure is 0.7 - 0.9 MPa.

5. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that The weight percentages of the components in the alloy powder are: Cr 12.31% - 12.76%, Ti 24.25% - 25.10%, Si 0.07% - 0.12%, HBN 0.04% - 0.09%, C 0.12% - 0.16%, and the balance is Ni.

6. The surface melting and plating process of the vacuum pump according to claim 5, wherein The weight percentages of the components in the alloy powder are: Cr 12.57%, Ti 24.85%, Si 0.09%, HBN 0.07%, C 0.15%, and the balance is Ni.

7. The surface melting and plating process of the vacuum pump according to claim 1, wherein, The particle size of the alloy powder is 45 - 55 μm.

8. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that, In step S2, the laser power of the laser is 4.5 - 5.0 kW, the beam diameter is 3 mm, the scanning speed is 13 - 15 mm / s, and the gas flow rate of the inert gas is 20 - 23 L / min.

9. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that, In step S2, the thickness of the molten coating is 1.2 - 1.5 mm.

10. The surface melting and plating process of the vacuum pump according to claim 1, characterized in that, The specific steps of the segmented heat treatment in step S3 are: Heat the melt-plated vacuum pump to 500 - 530 °C, keep it warm for 4 - 4.5 h, after cooling, continue to heat it to 320 - 330 °C, keep it warm for 3.4 - 4 h, and then cool it.

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