A method for surface thermal spraying and cryogenic press strengthening of rotating body parts

Abstract

The present application relates to the surface strengthening technical field of rotating body type parts, in particular to a rotating body type part surface thermal spraying-cryogenic ironing and pressing strengthening method, comprising: (1) initial grinding; (2) first stress relief treatment; (3) first coloring and flaw detection; (4) first cryogenic ironing and pressing treatment; (5) surface pretreatment; (6) preheating before spraying; (7) part spraying; (8) fine grinding; (9) second stress relief treatment; (10) second cryogenic ironing and pressing treatment; (11) second coloring and flaw detection. The present application provides a rotating body type part surface thermal spraying-cryogenic ironing and pressing strengthening method, which effectively improves the wear resistance, fatigue resistance, corrosion resistance and surface integrity and other comprehensive performance of the rotating body type part, significantly improves the service life of the part, can be widely applied in the field of aviation rotating body type part manufacturing and repair technology, and has significant economic benefits.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology for rotating body parts, specifically a method for strengthening the surface of rotating body parts by thermal spraying and deep cold pressing. Background Technology

[0002] Aerospace rotating parts typically operate in harsh environments characterized by high corrosiveness, wear, and high fatigue loads. After cyclical service, these parts are prone to severe wear, scratches, dimensional deviations, fatigue cracking, and deep corrosion pits, leading to component failure. In aerospace manufacturing and maintenance, chrome plating is widely used to protect the surface of rotating parts. However, this method has a long production cycle and often results in grinding marks, poor sealing, and hydrogen embrittlement. Some rotating parts also utilize thermal spraying of metal-ceramic coatings, primarily to improve wear resistance or corrosion resistance. However, this method can even decrease the fatigue performance of the parts.

[0003] Thermal spraying technology is a technique that uses a heat source to heat the spray powder to a molten or semi-molten state and then sprays it at supersonic speed onto the surface of a pretreated substrate material to form a coating. Among them, thermal sprayed metal-ceramic coatings have the characteristics of high bonding strength and excellent wear and corrosion resistance, and have been widely used in the fields of corrosion resistance, wear protection of parts surfaces, and replacement of electroplated hard chrome layers.

[0004] The deep cryogenic pressing process for metals uses elastic diamond tools to press the surface of parts and injects liquid nitrogen to achieve a low-temperature environment. It has the characteristics of significant effect, deep and large residual compressive stress field, small surface roughness and low cost. It can not only greatly improve its fatigue performance, but also significantly improve its resistance to stress corrosion cracking.

[0005] Applying both of the above processes to the surface of rotating parts to prepare a reinforcing coating can effectively improve the overall performance of the parts. Summary of the Invention

[0006] This invention aims to provide a method for strengthening the surface of rotating parts by thermal spraying and deep cryogenic pressing. It overcomes the shortcomings of chrome plating (the traditional protection method for rotating parts) such as surface porosity and poor sealing, as well as the disadvantage that a single thermal spraying metal-ceramic coating cannot provide good comprehensive protection performance. By combining thermal spraying metal-ceramic process with deep cryogenic pressing process, the comprehensive performance of rotating parts can be greatly improved, and it has the advantages of good economy and strong process operability.

[0007] The technical problem to be solved by this invention is achieved by the following technical solution:

[0008] A method for strengthening the surface of rotating parts by thermal spraying and deep cryogenic pressing includes the following steps:

[0009] (1) Initial grinding: The surface area to be processed of rotating parts is ground by machining;

[0010] (2) First stress relief treatment: stress relief treatment is performed on parts with strength σb≥1300Mpa after grinding;

[0011] (3) First dyeing flaw detection: After stress relief treatment, dyeing flaw detection is performed on the coating surface. It is required that there are no cracks in the reinforced parts and transition areas of the rotating body parts. If crack defects are found, rework and repeat the process (1) to (2) until the flaw detection is qualified.

[0012] (4) First cryogenic pressing treatment: The surface of rotating parts is pressed using a diamond elastic tool and the first cryogenic pressing process parameters are set. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication.

[0013] The parameters for a single deep cold ironing process are as follows:

[0014] The ironing depth is 0.010–0.020 mm, the lathe speed is 500–1000 rpm, the feed rate is 0.005–0.010 mm, and the number of ironing passes is 2–3.

[0015] (5) Surface pretreatment: For the surface to be sprayed, use 60-80 mesh brown fused alumina or white fused alumina sand and set the sandblasting process parameters to roughen the surface. After sandblasting, use clean and dry compressed air to blow away the residual sand particles. The surface of the rotating parts after sandblasting should be a rough state without metallic luster, with a roughness Ra of 5.0-7.6 μm.

[0016] The sandblasting process parameters are as follows:

[0017] The sandblasting pressure is 0.25-0.35MPa, the sandblasting distance is 150-200mm, the number of sandblasting passes is 2-4, the sandblasting gun should not stay on the workpiece for more than 15 seconds, and the sandblasting area should completely cover the surface to be repaired.

[0018] (6) Preheating before spraying: If the room temperature is below 5℃ or the humidity is above 75%, preheating is required before spraying rotating parts. Use a spray gun to preheat the rotating parts evenly without powder feeding. Use an infrared thermometer to measure the temperature of the rotating parts. The preheating temperature should not exceed 100℃.

[0019] (7) Parts spraying: The coating is prepared by using supersonic flame spraying process and setting supersonic flame spraying process parameters. During the spraying process, the temperature of rotating parts should not exceed the aging or annealing temperature of the substrate. During the spraying process and when the spraying is paused, clean compressed air or nitrogen is used to blow and cool the rotating parts or intermittent spraying is adopted. The next spraying is carried out after the surface temperature of the rotating parts drops to 40-55℃. The spraying interval should not exceed 1 hour. Before re-spraying, the dust on the coating surface should be blown off with compressed air.

[0020] The parameters for supersonic flame spraying are as follows:

[0021] The coating material is WC-12Co, WC-17Co, WC-10Co4Cr or Cr2Cr3-25NiCr powder, with a powder particle size of 15-53μm. The spraying carrier gas is nitrogen, with an oxygen flow rate of 1900-2030SCFH, a kerosene flow rate of 6.3-6.7GPH, an oxygen-fuel ratio of 299-315, a powder feeding rate of 47-68g / min, a relative moving speed of the spray gun of 800-1200mm / s, and a distance of 320-360mm between the spray gun and the part.

[0022] (8) Fine grinding: The surface of the rotating parts after spraying is ground to the upper limit of the dimensional accuracy requirements of the drawing, and the roughness is not worse than Ra3.2μm;

[0023] (9) Secondary stress relief treatment: stress relief treatment shall be carried out within 24 hours after the grinding of parts with strength σb≥1300Mpa;

[0024] (10) Secondary cryogenic pressing: The surface of rotating parts is pressed by using diamond elastic tools and setting secondary cryogenic pressing process parameters. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication.

[0025] The parameters for the secondary deep cold ironing process are as follows:

[0026] The ironing depth is 0.005–0.008 mm, the lathe speed is 300–500 rpm, the feed rate is 0.003–0.005 mm, and the number of ironing passes is 1–2.

[0027] (11) Secondary colorimetric testing: After stress relief treatment, the coating surface is subjected to colorimetric testing. It is required that there are no cracks in the reinforced parts and transition areas of the part surface. If cracks are found, the process (1) to (10) is repeated until the test is qualified.

[0028] As a further improvement of the present invention, the stress relief regime in process (2) is 190℃±10℃ / t≥4h.

[0029] As a further improvement of the present invention, the time interval between process (5) and process (7) shall not exceed 2 hours.

[0030] As a further improvement of the present invention, in step (7), when the rotating body part is made of steel, the base temperature does not exceed 177°C, and when the rotating body part is made of titanium alloy, the base temperature does not exceed 150°C.

[0031] As a further improvement of the present invention, the stress relief regime in process (9) is: 190℃±10℃ / t≥4h.

[0032] The beneficial effects of this invention are:

[0033] This invention provides a thermal spraying-cryogenic pressing method for strengthening the surface of rotating parts. Compared with existing technologies, this invention overcomes the shortcomings of chrome plating (the traditional protection method for rotating parts) by combining thermal spraying metal-ceramic technology with cryogenic pressing, such as surface porosity and poor sealing, as well as the disadvantage that a single thermal spraying metal-ceramic coating cannot provide good comprehensive protection. This effectively improves the wear resistance, fatigue resistance, corrosion resistance, and surface integrity of rotating parts, significantly extending their service life. It can be widely applied in the manufacturing and repair technology of aerospace rotating parts, with significant economic benefits. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0036] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0037] like Figure 1 As shown, a method for strengthening the surface of rotating parts by thermal spraying and deep cryogenic pressing, taking a steel part with a size of Ф50 as an example, includes the following steps:

[0038] (1) Initial grinding: The surface area to be processed of rotating parts is ground by machining.

[0039] (2) First stress relief treatment: After grinding, the parts with strength σb≥1300Mpa are subjected to stress relief treatment. The stress relief regime is 190℃±10℃ / t≥4h.

[0040] (3) First dyeing flaw detection: After stress relief treatment, dyeing flaw detection is performed on the coating surface. It is required that there are no cracks in the reinforced parts and transition areas of the rotating body parts. If crack defects are found, rework and repeat the process (1) to (2) until the flaw detection is qualified.

[0041] (4) First cryogenic pressing treatment: The surface of rotating parts is pressed using a diamond elastic tool and the first cryogenic pressing process parameters are set. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication.

[0042] The parameters for a single deep cold ironing process are as follows:

[0043] The ironing depth is 0.010–0.020 mm, the lathe speed is 500–1000 rpm, the feed rate is 0.005–0.010 mm, and the number of ironing passes is 2–3.

[0044] In this embodiment, the flow rate of liquid nitrogen is specifically controlled at 0.1 L / min, and the specific parameters of the single deep cryogenic ironing process are: ironing depth of 0.010 mm, lathe speed of 500 rpm, feed rate of 0.005 mm, and ironing passes of 2.

[0045] (6) Surface pretreatment: For the surface to be sprayed, use 60-80 mesh brown fused alumina or white fused alumina sand and set the sandblasting process parameters to roughen the surface. After sandblasting, use clean and dry compressed air to blow away the residual sand particles. The surface of the rotating parts after sandblasting should be a rough state without metallic luster, with a roughness Ra of 5.0-7.6 μm.

[0046] The sandblasting process parameters are as follows:

[0047] The sandblasting pressure is 0.25-0.35MPa, the sandblasting distance is 150-200mm, the number of sandblasting passes is 2-4, the sandblasting gun should not stay on the workpiece for more than 15 seconds, and the sandblasting area should completely cover the surface to be repaired.

[0048] In this embodiment, 60-mesh white corundum abrasive is used, the blasting pressure is 0.35 MPa, the blasting distance is 200 mm, and the number of blasting passes is 4. The surface roughness Ra is 5.0 μm.

[0049] (6) Preheating before spraying: If the room temperature is below 5℃ or the humidity is above 75%, preheating is required before spraying rotating parts. Use a spray gun to preheat the rotating parts evenly without powder feeding. Use an infrared thermometer to measure the temperature of the rotating parts. The preheating temperature should not exceed 100℃.

[0050] (7) Parts spraying: The coating is prepared by using supersonic flame spraying process and setting supersonic flame spraying process parameters. During the spraying process, the temperature of rotating parts should not exceed the aging or annealing temperature of the substrate. During the spraying process and when the spraying is paused, clean compressed air or nitrogen is used to blow and cool the rotating parts or intermittent spraying is adopted. The next spraying is carried out after the surface temperature of the rotating parts drops to 40-55℃. The spraying interval should not exceed 1 hour. Before re-spraying, the dust on the coating surface should be blown off with compressed air.

[0051] The parameters for supersonic flame spraying are as follows:

[0052] The coating material is WC-12Co, WC-17Co, WC-10Co4Cr or Cr2Cr3-25NiCr powder, with a powder particle size of 15-53μm. The spraying carrier gas is nitrogen, with an oxygen flow rate of 1900-2030SCFH, a kerosene flow rate of 6.3-6.7GPH, an oxygen-fuel ratio of 299-315, a powder feeding rate of 47-68g / min, a relative moving speed of the spray gun of 800-1200mm / s, and a distance of 320-360mm between the spray gun and the part.

[0053] In this embodiment, the specific parameters of the supersonic flame spraying process are as follows: the coating material is Cr2Cr3-25NiCr powder, the powder particle size is 53μm, the spraying carrier gas is nitrogen, the oxygen flow rate is 1900SCFH, the kerosene flow rate is 6.7GPH, the oxygen-fuel ratio of oxygen flow rate / kerosene flow rate is 299-315, the powder feeding rate is 68g / min, the relative moving speed of the spray gun is 1200mm / s, and the distance between the spray gun and the part is 360mm. During the spraying process and when the spraying is paused, clean compressed air is used to cool the rotating parts. The next spraying is carried out only after the surface temperature of the rotating parts drops to 55°C.

[0054] (8) Fine grinding: The surface of the rotating parts after spraying is ground to the upper limit of the dimensional accuracy requirements of the drawing, and the roughness is not worse than Ra3.2μm.

[0055] (9) Secondary stress relief treatment: stress relief treatment shall be carried out within 24 hours after the grinding of parts with strength σb≥1300Mpa. The stress relief regime is: 190℃±10℃ / t≥4h.

[0056] (10) Secondary cryogenic pressing: The surface of rotating parts is pressed by using diamond elastic tools and setting secondary cryogenic pressing process parameters. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication.

[0057] The parameters for the secondary deep cold ironing process are as follows:

[0058] The ironing depth is 0.005-0.008mm, the lathe speed is 300-500rpm, the feed rate is 0.003-0.005mm, and the number of ironing passes is 1-2.

[0059] In this embodiment, the flow rate of liquid nitrogen is specifically controlled at 0.3 L / min, and the specific parameters of the secondary cryogenic ironing process are: ironing depth of 0.005 mm, lathe speed of 500 rpm, feed rate of 0.003 mm, and ironing passes of 2.

[0060] (11) Secondary colorimetric testing: After stress relief treatment, the coating surface is subjected to colorimetric testing. It is required that there are no cracks in the reinforced parts and transition areas of the part surface. If cracks are found, the process (1) to (10) is repeated until the test is qualified.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for strengthening the surface of rotating body parts by thermal spraying and deep cryogenic pressing, characterized in that: Includes the following steps: (1) Initial grinding: The surface area to be processed of rotating parts is ground by machining; (2) First stress relief treatment: stress relief treatment is performed on parts with strength σb≥1300Mpa after grinding; (3) First dyeing flaw detection: After stress relief treatment, dyeing flaw detection is performed on the coating surface. It is required that there are no cracks in the reinforced parts and transition areas of the rotating body parts. If crack defects are found, rework and repeat the process (1) to (2) until the flaw detection is qualified. (4) First cryogenic pressing treatment: The surface of rotating parts is pressed using a diamond elastic tool and the first cryogenic pressing process parameters are set. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication. The parameters for a single deep cold ironing process are as follows: The ironing depth is 0.010–0.020 mm, the lathe speed is 500–1000 rpm, the feed rate is 0.005–0.010 mm, and the number of ironing passes is 2–3. (5) Surface pretreatment: For the surface to be sprayed, use 60-80 mesh brown fused alumina or white fused alumina sand and set the sandblasting process parameters to roughen the surface. After sandblasting, use clean and dry compressed air to blow away the residual sand particles. The surface of the rotating parts after sandblasting should be a rough state without metallic luster, with a roughness Ra of 5.0-7.6 μm. The sandblasting process parameters are as follows: The sandblasting pressure is 0.25-0.35MPa, the sandblasting distance is 150-200mm, the number of sandblasting passes is 2-4, the sandblasting gun should not stay on the workpiece for more than 15 seconds, and the sandblasting area should completely cover the surface to be repaired. (6) Preheating before spraying: If the room temperature is below 5℃ or the humidity is above 75%, preheating is required before spraying rotating parts. Use a spray gun to preheat the rotating parts evenly without powder feeding. Use an infrared thermometer to measure the temperature of the rotating parts. The preheating temperature should not exceed 100℃. (7) Parts spraying: The coating is prepared by using supersonic flame spraying process and setting supersonic flame spraying process parameters. During the spraying process, the temperature of rotating parts should not exceed the aging or annealing temperature of the substrate. During the spraying process and when the spraying is paused, clean compressed air or nitrogen is used to blow and cool the rotating parts or intermittent spraying is adopted. The next spraying is carried out after the surface temperature of the rotating parts drops to 40-55℃. The spraying interval should not exceed 1 hour. Before re-spraying, the dust on the coating surface should be blown off with compressed air. The parameters for supersonic flame spraying are as follows: The coating material is WC-12Co, WC-17Co, WC-10Co4Cr or Cr2Cr3-25NiCr powder, with a powder particle size of 15-53μm. The spraying carrier gas is nitrogen, with an oxygen flow rate of 1900-2030SCFH, a kerosene flow rate of 6.3-6.7GPH, an oxygen-fuel ratio of 299-315, a powder feeding rate of 47-68g / min, a relative moving speed of the spray gun of 800-1200mm / s, and a distance of 320-360mm between the spray gun and the part. (8) Fine grinding: The surface of the rotating parts after spraying is ground to the upper limit of the dimensional accuracy requirements of the drawing, and the roughness is not worse than Ra3.2μm; (9) Secondary stress relief treatment: stress relief treatment shall be carried out within 24 hours after the grinding of parts with strength σb≥1300Mpa; (10) Secondary cryogenic pressing: The surface of rotating parts is pressed by using diamond elastic tools and setting secondary cryogenic pressing process parameters. During the pressing process, liquid nitrogen is continuously poured at a flow rate of 0.1 to 0.3 L / min to provide a low temperature environment and lubricating oil is injected for surface lubrication. The parameters for the secondary deep cold ironing process are as follows: The ironing depth is 0.005–0.008 mm, the lathe speed is 300–500 rpm, the feed rate is 0.003–0.005 mm, and the number of ironing passes is 1–2. (11) Secondary colorimetric testing: After stress relief treatment, the coating surface is subjected to colorimetric testing. It is required that there are no cracks in the reinforced parts and transition areas of the part surface. If cracks are found, the process (1) to (10) is repeated until the test is qualified.

2. The method for strengthening the surface of a rotating body part by thermal spraying and deep cryogenic pressing according to claim 1, characterized in that: The stress relief regime in process (2) is 190℃±10℃ / t≥4h.

3. The method for strengthening the surface of a rotating body part by thermal spraying and deep cryogenic pressing according to claim 1, characterized in that: The time interval between process (5) and process (7) shall not exceed 2 hours.

4. The method for strengthening the surface of a rotating body part by thermal spraying and deep cryogenic pressing according to claim 1, characterized in that: In process (7), when the rotating body part is made of steel, the base temperature shall not exceed 177°C; when the rotating body part is made of titanium alloy, the base temperature shall not exceed 150°C.

5. The method for strengthening the surface of a rotating body part by thermal spraying and deep cryogenic pressing according to claim 1, characterized in that: The stress relief regime in process (9) is: 190℃±10℃ / t≥4h.

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