A vacuum pump surface molten plating process

Abstract

The present invention belongs to the technical field of surface engineering treatment, and specifically relates to a vacuum pump surface melting and plating process. The vacuum pump surface melting and plating process provided by the present invention includes the steps of activation treatment, vacuum melting and plating, heat treatment and mechanical processing. The present invention activates the surface of the vacuum pump by sandblasting activation and pickling activation, effectively improving the bonding strength between the vacuum pump and the coating; by preheating the vacuum pump before melting and plating, and adopting a higher laser intensity and a faster scanning speed for laser melting and plating, the obtained coating has higher hardness and good wear resistance; by improving the formula of the alloy powder and controlling the amount of the formula components, the wear resistance and impact resistance of the coating are further improved; by performing segmented heat treatment on the vacuum pump after melting and plating, the thermal stress in the vacuum pump coating is effectively eliminated, and the cracking or shedding of the coating caused by stress concentration is effectively avoided.

Description

Technical Field

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

[0002] Vacuum pumps can extract gas or steam from the system, reduce system pressure, and create the required vacuum environment, thereby realizing various operations in the chemical production process, ensuring product quality and production efficiency. They are used in industrial manufacturing, scientific research, medical care, aerospace and other fields, and continuously promote technological progress and efficiency improvement in various industries.

[0003] With the continuous development and advancement of the chemical industry, the requirements for vacuum pumps are becoming increasingly stringent. The pump casing, sealing liquid disc, and pump cover of a vacuum pump are all made of gray cast iron. Gray cast iron is convenient for casting complex components, but cast iron has low strength and poor corrosion resistance. To improve the performance and lifespan of vacuum pumps, coating processes are required on the surface of the vacuum pump. Common coating methods include physical vapor deposition, chemical vapor deposition, electroplating, and melt plating. Melt plating, being adaptable to substrates of various shapes and sizes and requiring relatively low substrate material requirements, has become the mainstream coating process for vacuum pumps. The melt plating process heats the coating material to a liquid state using a high-temperature heat source. Leveraging the fluidity and wettability of the liquid metal, it is uniformly coated on the substrate surface under the influence of gravity, centrifugal force, and pressure. As the liquid metal rapidly cools and solidifies, it forms a strong bond with the substrate, thereby improving the substrate's surface properties. Common molten metal deposition processes include hot-dip plating, spray-melt plating, cladding cladding, and laser cladding. However, the high preparation costs of hot-dip plating and thermal spraying limit their large-scale engineering application and promotion. Cladding cladding requires high process parameters and operating techniques, and unfused layers may occur between the cladding layer and the substrate, or between cladding layers, affecting the performance of the film material. The laser cladding process has a fast cooling rate, which can form a fine-grained structure within the material, and has a low dilution rate. The cladding layer and the substrate form a strong metallurgical bond or interface diffusion bond. However, the conventional laser cladding process requires a high heat input from the vacuum pump, which can easily form large residual stresses, leading to cracks in the cladding layer, affecting the microstructure and performance of the cladding layer, and shortening its service life.

[0004] A Chinese patent application document with publication number CN107130240A discloses a laser cladding method, comprising: using the protective cover to buckle the metal substrate to be processed; introducing an inert gas through the first air inlet on the outer layer to fill the space of the protective cover; 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 so that the laser beam generated by the laser will 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 large, and the performance difference between the cladding layer and the substrate material is also large. Stress concentration will occur at the bonding interface due to technical problems such as the solidification of the cladding metal and the difference in material properties. When bearing loads, the stress concentration points in the coating are prone to fatigue and cause the coating to fall off, affecting the appearance and corrosion resistance of the coating. Summary of the Invention

[0005] In order to solve the technical problems in the prior art of high stress on the molten-plated layer of vacuum pumps, weak bonding with the substrate, easy falling off, and prone to microcracks or falling off, the present invention provides a surface molten-plating process for vacuum pumps.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A vacuum pump surface melting plating process comprises the following steps:

[0008] S1: activating the surface of the vacuum pump to obtain a spare vacuum pump;

[0009] S2: preheating the spare vacuum pump prepared in step S1 to 100-120°C and keeping the temperature for 1-1.5 hours, then adding alloy powder into the spray gun and continuously feeding powder to the surface of the vacuum pump at which the laser head is aligned through a laser coaxial powder feeding system, scanning the surface of the vacuum pump to which the alloy powder is attached with a laser to form a melt-plated layer, and using an inert gas to protect the melt-plated area during the melt-plating process to obtain a melt-plated vacuum pump;

[0010] S3: performing a segmented heat treatment on the molten-plated vacuum pump obtained in step S2 to obtain a heat-treated vacuum pump;

[0011] S4: Mechanically process the heat-treated vacuum pump obtained in step S3 to remove excess surface layer;

[0012] The alloy powder includes Cr, Ti, Si, HBN, C, and Ni.

[0013] In the above technical solution, heating the standby vacuum pump to 100-120°C in step S2 can effectively remove moisture from the surface of the standby vacuum pump and improve the bonding strength between the alloy powder and the substrate. At the same time, within this temperature range, the dilution rate of the cladding layer is low, and the temperature difference with the molten pool is large, and the cooling rate of the cladding layer is large, which is conducive to refining the grain structure of the cladding layer and achieving the effect of fine grain strengthening.

[0014] The Cr in the alloy powder solid-solution strengthens the Ni matrix, enhancing the corrosion resistance of the Ni-based alloy. Cr also reacts with C to form Cr7C3, which is dispersed throughout the Ni-based alloy matrix, providing dispersion strengthening and significantly improving the wear resistance of the alloy coating. Si forms a eutectic with Ni and Fe, significantly lowering the alloy's melting point. Si, a strong oxygen-affinity element, reduces oxides on the metal surface to form SiO2, which forms a borosilicate glass with other metal oxides. This glass has excellent fluidity and readily floats in the liquid alloy, coating the molten metal and preventing oxidation. Furthermore, Si forms a Si-Ni solid solution in the Ni austenite, resulting in solid-solution strengthening and enhancing the alloy's strength. HBN (hexagonal boron nitride) exhibits excellent lubricity and chemical stability, effectively reducing the sintering temperature of the alloy powder. Its dispersion within the Ni alloy matrix effectively inhibits dislocation motion, preventing deformation of the alloy coating under stress, thereby improving the wear resistance of the coating. Segmented heat treatment of the molten-plated vacuum pump can effectively remove the thermal stress in the molten-plated layer, avoid cracks and shedding caused by stress concentration in the coating, and extend the service life of the vacuum pump.

[0015] Furthermore, the activation treatment in step S1 includes sandblasting activation and pickling activation, wherein the sandblasting activation uses iron sand, and the pickling activation uses phosphoric acid solution.

[0016] In the above technical solution, sandblasting activation uses iron sand with higher density, which can form deeper pits on the surface of the vacuum pump during the activation process, thereby improving the adhesion of the coating on the surface of the vacuum pump and preventing it from falling off; pickling activation uses phosphoric acid solution to chemically react with the oxides on the surface of the vacuum pump to dissolve and remove them, while making the surface of the vacuum pump active. The phosphate film on the surface of the vacuum pump after pickling helps to improve the adhesion of the coating.

[0017] Furthermore, the activation treatment in step S1 is specifically as follows: selecting iron sand with a particle size of 40-50 mesh to sandblast the vacuum pump, the sandblasting pressure is 0.5-0.7 MPa, the treatment time is 20-30 min, and after cleaning, the vacuum pump is placed in a phosphoric acid solution with a concentration of 1.5-2.3 mol / L, heated to 50-60°C for 20-30 min, and then removed and washed with water until the washing liquid is neutral.

[0018] Furthermore, the powder output of the spray gun in step S2 is 35-40 g / min, and the powder supply pressure is 0.7-0.9 MPa.

[0019] Furthermore, 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 Ni as the balance.

[0020] 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 limits of the present invention, more brittle silicon oxide and silicate compounds will appear on the grain boundaries of the alloy coating, and the toughness of the alloy coating will be reduced. When subjected to external force, cracks may occur or even fall off.

[0021] Furthermore, 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 Ni balance.

[0022] Furthermore, the particle size of the alloy powder is 45-55 μm.

[0023] Furthermore, 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 flow rate of the inert gas is 20-23 L / min.

[0024] In the above-mentioned technical solution, the power and scanning speed of the laser will affect the structure and performance of the molten deposit. Research has found that within the power and scanning speed range of the laser provided by the present invention, the structure of the molten deposit becomes fine, the surface stress is reduced, the number of cracks is reduced, and the amorphous phase content in the molten deposit increases, and the fiber hardness and wear resistance are significantly improved. This is because higher laser power can rapidly heat up and then cool the alloy powder, making the temperature gradient of the molten pool higher and more gentle, effectively reducing stress concentration, accelerating atomic diffusion, facilitating the formation of more crystal nuclei, and reducing the formation of microcracks; while excessively fast scanning speed shortens the residence time of the molten pool, reducing heat accumulation inside the molten pool, increasing the degree of supercooling in the molten pool, facilitating the formation of crystal nuclei, and playing a role in refining the grains.

[0025] Furthermore, the thickness of the melt-plated layer in step S2 is 1.2-1.5 mm.

[0026] Furthermore, the specific steps of the segmented heat treatment in step S3 are: heating the melt plating vacuum pump to 500-530°C, keeping it warm for 4-4.5 hours, cooling it and then continuing to heat it to 320-330°C, keeping it warm for 3.4-4 hours, and cooling it.

[0027] Through the above technical solution, the melt plating vacuum pump is heated to 500-530℃, the atoms in the substrate and the coating are further diffused, and the residual stress in the coating is effectively released through the rearrangement of atoms, thereby improving the bonding strength between the coating and the substrate. Keeping it warm for 4-4.5 hours can effectively promote recrystallization and grain refinement inside the coating, making the microstructure of the coating more uniform; after cooling, it is heated again to 320-330℃. Within this temperature range, the thermal stress in the coating can be further released, further playing the role of grain refinement and strengthening, and improving the wear resistance of the coating.

[0028] Compared with the existing technology, the vacuum pump surface molten plating process provided by the present invention has the following technical advantages:

[0029] (1) The present invention activates the surface of the vacuum pump by sandblasting activation and pickling activation, thereby effectively improving the bonding strength between the vacuum pump and the coating;

[0030] (2) The present invention preheats the vacuum pump before laser plating and uses a higher laser intensity and a faster scanning speed for laser plating, so that the obtained coating has higher hardness and good wear resistance;

[0031] (3) The present invention improves the formula of the alloy powder and controls the amount of the formula components, so that the obtained coating has good corrosion resistance, wear resistance and impact resistance;

[0032] (4) The present invention effectively eliminates the thermal stress in the vacuum pump coating by performing segmented heat treatment on the vacuum pump after melt plating, and effectively avoids cracks or shedding of the coating caused by stress concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a scanning electron microscope image of the coating prepared in Example 1;

[0034] Figure 2 This is a scanning electron microscope image of the coating prepared in Example 2;

[0035] Figure 3 This is a scanning electron microscope image of the coating prepared in Example 3. DETAILED DESCRIPTION

[0036] 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 may make various modifications based on the basic concept of the present invention, but as long as they do not depart from the basic concept of the present invention, they are all within the scope of the present invention.

[0037] The laser used in this embodiment utilizes an LDM 6000-100 semiconductor laser, resulting in a relatively uniform laser spot energy distribution. The laser spot diameter is 3 mm, and a HINO50W coaxial annular high-speed powder feed nozzle is used, resulting in a powder convergence spot diameter no larger than 1.5 mm. A PF2-2 dual-cylinder synchronous powder feeder is employed, with argon as the powder feed gas.

[0038] In this specific embodiment, in order to facilitate the detection of the melt-plated layer, a gray cast iron sheet made of the same material as the vacuum pump is used instead of the vacuum pump for the surface melt-plating process. The size of the gray cast iron sheet is 10mm×10mm×5mm, and the chemical composition of the gray cast iron sheet is: C2.8%, Si1.5%, Mn1.0%, P0.08%, S0.05%, and Fe remainder.

[0039] Example 1

[0040] A vacuum pump surface melting plating process comprises the following steps:

[0041] S1: activating the surface of the vacuum pump to obtain a spare vacuum pump; the activation treatment specifically comprises: sandblasting the vacuum pump with iron sand of 40 mesh particle size at a sandblasting pressure of 0.5 MPa for 30 minutes; after cleaning, placing the vacuum pump in a phosphoric acid solution of 1.5 mol / L, heating it to 50° C. for 30 minutes, and then removing it from the vacuum pump and washing it with water until the washing liquid is neutral;

[0042] S2: preheating the spare vacuum pump prepared in step S1 to 100°C and keeping it warm for 1.5 hours, then adding alloy powder with a particle size of 45 μm into the spray gun and continuously feeding powder to the surface of the vacuum pump at which the laser head is aligned through a laser coaxial powder feeding system, with the spray gun having a powder output of 35 g / min and a powder supply pressure of 0.7 MPa; scanning the surface of the vacuum pump to which the alloy powder is attached with a laser to form a melt-plated layer with a thickness of 1.2 mm, and using an inert gas to protect the melt-plated area during the melt-plating process to obtain a melt-plated vacuum pump; the laser power of the laser is 4.5 kW, the beam spot diameter is 3 mm, the scanning speed is 13 mm / s, and the inert gas flow rate is 20 L / min;

[0043] S3: heating the melt-plated vacuum pump obtained in step S2 to 500° C., keeping the temperature for 4.5 hours, cooling, and then continuing to heat to 320° C., keeping the temperature for 4 hours, and cooling to obtain a heat-treated vacuum pump;

[0044] S4: Mechanically process the heat-treated vacuum pump obtained in step S3 to remove excess surface layer;

[0045] The alloy powder includes the following components in weight percentage: Cr12.31%, Ti24.25%, Si0.07%, HBN0.04%, C0.12%, and Ni balance.

[0046] Example 2

[0047] A vacuum pump surface melting plating process comprises the following steps:

[0048] S1: activating the surface of the vacuum pump to obtain a spare vacuum pump; the activation treatment specifically comprises: sandblasting the vacuum pump with iron sand of 50 mesh particle size at a sandblasting pressure of 0.7 MPa for 20 minutes; after cleaning, placing the vacuum pump in a 2.3 mol / L phosphoric acid solution, heating it to 60°C for 20 minutes, and then removing it from the vacuum pump and washing it with water until the washing liquid is neutral;

[0049] S2: preheating the spare vacuum pump prepared in step S1 to 120°C and keeping it warm for 1.5 hours, then adding alloy powder with a particle size of 55 μm into the spray gun and continuously feeding powder to the surface of the vacuum pump at which the laser head is aligned through a laser coaxial powder feeding system, with the spray gun having a powder output of 40 g / min and a powder supply pressure of 0.9 MPa; scanning the surface of the vacuum pump to which the alloy powder is attached with a laser to form a melt-plated layer with a thickness of 1.5 mm, and protecting the melt-plated area with an inert gas during the melt-plating process to obtain a melt-plated vacuum pump; the laser power of the laser is 5.0 kW, the beam spot diameter is 3 mm, the scanning speed is 15 mm / s, and the inert gas flow rate is 23 L / min;

[0050] S3: heating the molten plating vacuum pump obtained in step S2 to 530° C., keeping the temperature for 4 hours, cooling and then continuing to heat to 330° C., keeping the temperature for 3.4 hours, and cooling to obtain a heat-treated vacuum pump;

[0051] S4: Mechanically process the heat-treated vacuum pump obtained in step S3 to remove excess surface layer;

[0052] The alloy powder includes the following components in weight percentage: Cr12.76%, Ti25.10%, Si0.12%, HBN0.09%, C0.16%, and Ni balance.

[0053] Example 3

[0054] A vacuum pump surface melting plating process comprises the following steps:

[0055] S1: activating the surface of the vacuum pump to obtain a spare vacuum pump; the activation treatment specifically comprises: sandblasting the vacuum pump with iron sand having a particle size of 45 mesh at a sandblasting pressure of 0.6 MPa for 25 minutes; after cleaning, placing the vacuum pump in a phosphoric acid solution having a concentration of 1.8 mol / L, heating it to 55° C. for 26 minutes, and then removing the vacuum pump and washing it with water until the washing solution is neutral;

[0056] S2: preheating the spare vacuum pump prepared in step S1 to 115°C and keeping it warm for 1.2 hours, then adding alloy powder with a particle size of 50 μm into a spray gun and continuously feeding powder to the surface of the vacuum pump at which the laser head is aligned through a laser coaxial powder feeding system, with the spray gun having a powder output of 38 g / min and a powder supply pressure of 0.8 MPa; scanning the surface of the vacuum pump to which the alloy powder is attached with a laser to form a melt-plated layer with a thickness of 1.4 mm, and protecting the melt-plated area with an inert gas during the melt-plating process to obtain a melt-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 inert gas flow rate is 22 L / min;

[0057] S3: heating the molten plating vacuum pump obtained in step S2 to 525° C., keeping the temperature for 4.2 hours, cooling, and then continuing to heat to 325° C., keeping the temperature for 3.6 hours, and cooling to obtain a heat-treated vacuum pump;

[0058] S4: Mechanically process the heat-treated vacuum pump obtained in step S3 to remove excess surface layer;

[0059] 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 Ni as the balance.

[0060] Comparative Example 1

[0061] The vacuum pump surface melting plating process described 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.

[0062] Comparative Example 2

[0063] The vacuum pump surface melting and plating process described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the alloy powder described in step S2 of this comparative example uses an equal amount of Ni instead of HBN.

[0064] Comparative Example 3

[0065] The vacuum pump surface melting and plating process described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the alloy powder described in step S2 of this comparative example uses an equal amount of Ni instead of Si.

[0066] Comparative Example 4

[0067] The vacuum pump surface melting and plating process described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the alloy powder described in step S2 of this comparative example uses an equal amount of Ni instead of C.

[0068] Comparative Example 5

[0069] The vacuum pump surface melting and plating process described 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 described in step S2 of this comparative example is 3.0 kW.

[0070] Comparative Example 6

[0071] The vacuum pump surface melting and plating process 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 described in step S2 of this comparative example is 7 mm / s.

[0072] Comparative Example 7

[0073] The surface molten 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 the heat treatment in step S3 of this comparative example are: heating the molten plating vacuum pump to 325°C and keeping it warm for 7.8 hours.

[0074] Test example

[0075] Test samples: vacuum pump gray cast iron sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 7;

[0076] Hardness test: Rockwell hardness test is carried out on the test samples in accordance with GB / T 230.1-2018 "Rockwell hardness test for metallic materials". Each sample is measured at 3 points at different positions and the average value is calculated;

[0077] Impact resistance: GB / T 229-2020 "Charpy pendulum impact test method for metallic materials" is used to test the impact resistance of the test samples;

[0078] Wear resistance test: The friction and wear test was conducted using an RTEC MFT-5000 friction and wear tester with a load of 30N, a sliding speed of 0.06m / s, and a wear time of 20min. The friction partner was a 6mm diameter high-carbon steel ball. An OLS-4100 laser confocal microscope was used to measure the width and depth of the wear scar to calculate the wear volume. The wear rate W is calculated as W=V / LS, where: V is the wear volume (mm 3 ), L is the loading load (N), S is the sliding displacement (m);

[0079] Residual stress test: The residual stress on the surface of the cladding layer was measured using a Stress-X residual stress measuring instrument. The X-ray anode tube used a Cr target Kα ray with a 2θ diffraction angle of 128°.

[0080] The test results are shown in Table 1.

[0081] Table 1 Performance test results

[0082]

[0083] As shown in Table 1, the hardness of the gray cast iron steel sheet coating obtained by the vacuum pump surface molten plating process provided by the present invention is 46-51, and the impact toughness is 712.7-721.3 kJ / m 2 , wear rate is 2.95-3.41mm 3 / (N·m), the residual stress of the coating is 33.5-35.2MPa, which fully demonstrates that the coating obtained by the vacuum pump surface melting plating process 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 falling off caused by stress concentration.

[0084] Compared with Example 3, the preheating temperature in step S2 of Comparative Example 1 is increased, but the hardness of the obtained coating is reduced, the impact toughness is reduced, and the wear rate is increased. This is because the high preheating temperature leads to a reduced cooling rate of the molten coating crystals, and the grain growth leads to coarse crystal dendrites, which leads to reduced hardness and toughness of the coating; in step S2 of Comparative Example 2, the alloy powder uses an equal amount of Ni instead of HBN, but the wear rate of the obtained coating is increased, which shows that HBN can effectively improve the wear resistance of the coating; in step S2 of Comparative Example 3, the alloy powder uses an equal amount of Ni instead of Si, and in step S2 of Comparative Example 4, the alloy powder uses an equal amount of Ni instead of C, but the hardness and impact resistance of the obtained coating are reduced, and the wear rate is increased. This shows that the addition of Si and C can form a solid solution dispersed in the coating, effectively improving the strength and wear resistance of the coating; in step S2 of comparative example 5, the laser power of the laser was reduced, and in step S2 of comparative example 6, the scanning speed was reduced, but the hardness and impact resistance of the obtained coating were reduced, and the wear rate was increased, which shows that higher laser power and scanning speed can be conducive to the formation of crystal nuclei and play a role in fine grain strengthening; in step S3 of comparative example 7, only low-temperature heat treatment was performed, but the impact resistance of the obtained coating was reduced and the residual stress was increased, which shows that heat treatment at 500-530°C for 4-4.5h in the present invention can effectively release the residual stress in the coating and improve the bonding strength between the coating and the substrate.

[0085] In addition, the present invention also conducted a scanning electron microscope test on the vacuum pump gray cast iron sheet coating obtained in Example 1 to Example 3, and the test results are shown in FIG. Figure 1-Figure 3 .Depend on Figure 1-Figure 3 It can be seen that no defects such as pores, cracks, and powder inclusions appear in the coatings produced by the vacuum pump melting and plating process provided by the present invention, which indicates that the coatings produced by the vacuum pump melting and plating process provided by the present invention have good microstructure and high melting and plating quality.

[0086] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A vacuum pump surface plating process, characterized in that: The following steps are involved: S1: activating the surface of the vacuum pump to obtain a spare vacuum pump; S2: preheating the spare vacuum pump prepared in step S1 to 100-120°C and maintaining the temperature for 1-1.5 hours, then adding nickel-based alloy powder to a spray gun and continuously feeding the powder to the surface of the vacuum pump at which the laser head is aligned through a laser coaxial powder feeding system, scanning the surface of the vacuum pump where the alloy powder is attached with a laser to form a melt-plated layer, and using an inert gas to protect the melt-plated area during the melt-plating process to obtain a melt-plated vacuum pump; S3: performing a segmented heat treatment on the molten-plated vacuum pump obtained in step S2 to obtain a heat-treated vacuum pump; S4: Mechanically process the heat-treated vacuum pump obtained in step S3 to remove excess surface layer; The nickel-based alloy powder consists of the following components: Cr, Ti, Si, HBN, C, and Ni; 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 inert gas flow rate is 20-23 L / min; The specific steps of the segmented heat treatment in step S3 are: heating the melt plating vacuum pump to 500-530° C., keeping the temperature for 4-4.5 hours, cooling and then continuing to heat to 320-330° C., keeping the temperature for 3.4-4 hours, and cooling.

2. The vacuum pump surface molten plating process 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 phosphoric acid solution.

3. The vacuum pump surface molten plating process according to claim 2, characterized in that: The activation treatment in step S1 is specifically as follows: selecting iron sand with a particle size of 40-50 mesh to sandblast the vacuum pump, the sandblasting pressure is 0.5-0.7 MPa, and the treatment time is 20-30 minutes. After cleaning, the vacuum pump is placed in a phosphoric acid solution with a concentration of 1.5-2.3 mol / L, heated to 50-60°C for 20-30 minutes, and then removed and washed with water until the washing liquid is neutral.

4. The vacuum pump surface molten plating process 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 vacuum pump surface molten plating process according to claim 1, characterized in that: The weight percentages of the components in the nickel-based 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 Ni as the balance.

6. The vacuum pump surface molten plating process according to claim 5, characterized in that: The weight percentages of the components in the nickel-based alloy powder are: Cr 12.57%, Ti 24.85%, Si 0.09%, HBN 0.07%, C 0.15%, and Ni as the balance.

7. The vacuum pump surface molten plating process according to claim 1, characterized in that: The particle size of the nickel-based alloy powder is 45-55 μm.

8. The vacuum pump surface molten plating process according to claim 1, characterized in that: The thickness of the melt-plated layer in step S2 is 1.2-1.5 mm.

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