Method for improving surface wear resistance of steel valve plate through laser 3D printing remelting texturing

Abstract

The invention relates to a method for improving the surface abrasion resistance of a steel valve plate through laser 3D printing remelting texturing. The method sequentially comprises the steps of base material pre-heating treatment, surface treatment, remelting micro-texture machining, stress relief annealing and surface polishing. According to the method, textures of different shapes and distributions are designed on a matrix with certain hardness by utilizing laser 3D printing equipment, other additional auxiliary materials do not need to be introduced, only micron-sized laser beams are adopted for remelting on the surface of a sample piece according to the designed pattern, and a micro-pit texture pattern with the diameter and depth of tens of micrometers to hundreds of micrometers can be obtained; on one hand, an extremely fine structure can be obtained through rapid cooling after a tiny molten pool is remelted, the micro-texture hard spot effect is obtained, on the other hand, the pit texture shape can serve as an oil storage point, stable friction conditions and a good oil film state can be formed easily, and therefore the abrasion resistance of the valve plate is improved. The method is very simple and convenient, high in production stability and high in machining precision.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metal material surface treatment, and particularly relates to a method for improving the wear resistance of a steel flow distribution disc surface by laser 3D printing remelting texturing. BACKGROUND

[0002] An axial plunger pump is a key component of a hydraulic system, and a flow distribution pair composed of a flow distribution disc and a cylinder body is one of important friction pairs of the axial plunger pump. The flow distribution disc plays a role in flow distribution and force balance maintenance of the cylinder body, and needs to have good wear resistance because it bears large friction during operation.

[0003] At present, the flow distribution disc usually needs to be subjected to surface treatment such as carburizing, nitriding, spraying and the like for surface strengthening. Composite materials such as laser cladding and vapor deposition are also used to obtain a surface composite strengthening layer. In addition, texturing treatment on the surface of a wear-resistant part can obtain a more favorable surface morphology, and is also a method for improving wear resistance.

[0004] At present, texturing is usually performed by using a laser, chemical etching or mechanical pressure etching and the like. Although these methods can obtain flexible texturing morphology, they also have problems such as difficulty in accurately controlling the texturing shape, high processing cost and low efficiency. SUMMARY

[0005] The application provides a method for improving the wear resistance of a steel flow distribution disc surface by laser 3D printing remelting texturing, and solves the defects of the prior art.

[0006] In order to solve the above technical problems, the application provides a method for improving the wear resistance of a steel flow distribution disc surface by laser 3D printing remelting texturing, characterized in that the following steps are sequentially performed in the order of: S1, placing a flow distribution disc sample subjected to heat treatment, stamping forming and surface grinding on a selective laser melting substrate for pre-temperature preservation; S2, performing laser remelting scanning according to a set texturing pattern to obtain a sample with a micro-texturing pattern; S3, performing stress relief annealing on the sample with the micro-texturing pattern; S4, performing surface polishing treatment on the sample after stress relief annealing to finally obtain a finished sample.

[0007] Beneficial effects: on the basis of obtaining a certain hardness of the substrate, using a laser 3D printing equipment, designing different shapes and distribution of texture, without additional introduction of other auxiliary materials, only using micron laser beam according to the designed pattern on the surface of the sample piece is remelted, the size of the micro concave texture pattern is obtained in tens to hundreds of microns in diameter and depth, on the one hand, the micro molten pool is rapidly cooled after remelting to obtain extremely fine organization, and the micro texture hard point effect is obtained, on the other hand, the concave texture shape can be used as an oil storage point, which is beneficial to form stable friction condition and good oil film state, so as to improve the wear resistance of the distribution disc. The method is very simple, the production stability is high, and the machining precision is high. It can be further combined with other surface treatment, which greatly expands the processing and application range of the surface texture treatment of the distribution disc, and has good popularization. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 Surface texture morphology of example 1; Figure 2 Surface texture pit morphology of example 1; Figure 3 Surface texture of example 3; Figure 4 Surface texture of example 3; Figure 5 Friction coefficient comparison of comparative example 1 and non-textured sample; Figure 6 Friction coefficient comparison of comparative example 2 and non-textured sample. DETAILED DESCRIPTION

[0009] In order to make the purpose, content and advantages of the present application more clear, the specific embodiments of the present application are described in further detail below.

[0010] The present application proposes a method for improving the wear resistance of the surface of the steel distribution disc by laser 3D printing remelting texture, which is carried out in the following order: S1, placing the distribution disc sample after heat treatment, stamping forming and surface grinding on the selected area laser melting substrate for pre-temperature preservation; S2, laser remelting scanning according to the set texture pattern to obtain a sample with micro texture pattern; S3, stress relief annealing of the sample with micro texture pattern; S4, surface polishing treatment of the sample after stress relief annealing to obtain the finished sample.

[0011] Specifically, in step S1, the sample heat treatment includes quenching, tempering and / or surface carburizing, nitriding, shot peening, cold thermal spraying and other methods, and the surface layer hardness is 50-55 HRC. The appropriate surface hardness ensures that the substrate has good wear resistance, while taking into account better elongation and impact resistance.

[0012] Specifically, in step S1, the surface roughness of the sample after grinding treatment is not more than Ra10 microns, so as to ensure that the substrate has good roughness, forms a good oil film during friction, and ensures that a relatively uniform pit depth can be obtained after the next micro-texture is formed.

[0013] Specifically, in step S1, the substrate heating temperature is set to 150-200℃, and the holding time is 0.5-1 hour, so as to ensure that stress concentration can be reduced during laser remelting, and cracking and deformation of the sample can be inhibited.

[0014] Specifically, in step S2, the size of the laser beam during laser remelting is set to 60-100 microns, so as to ensure that a small texture is obtained, and the size accuracy of the texture pattern is ensured.

[0015] Specifically, in step S2, laser remelting is performed at a laser power of 100-250W and a scanning speed of 200-500mm / s. Too low laser power makes it difficult to form enough remelted pits. Too high laser power will cause the remelted area to be too large, the molten pool to be unstable, the size of the formed texture pattern to be irregular, and the size accuracy to be difficult to guarantee. The appropriate scanning speed not only ensures high processing efficiency, but also plays a role in regulating the width-depth ratio of the molten pool.

[0016] Specifically, in step S2, the texture after laser remelting is a pit shape, with a diameter of 150-400 microns and a depth of 30-100 microns, and the shape is relatively uniform, and the size accuracy of the texture point distribution is not more than 50 microns.

[0017] Specifically, in step S3, stress relief annealing is performed in a vacuum heat treatment furnace, the heating temperature is 200-350℃, and the holding time is 1-2 hours. The appropriate temperature and time can not only remove the stress concentration introduced during processing, but also ensure that the substrate and remelted structure are not changed due to excessive heating, which affects the mechanical properties such as hardness.

[0018] Specifically, in step S4, the final polishing includes but is not limited to polishing methods such as abrasive belt and diamond, and the surface roughness after polishing reaches Ra10 microns. The purpose of polishing is to reduce the small protrusions around the remelted area, so as to ensure the stability and uniformity of the oil film during friction.

[0019] Example 1 This example is carried out for a GCr15 steel substrate, and the specific preparation method is as follows: S1, GCr15 steel is heat treated, the heat treatment process is: temperature 960℃, straight into the furnace for 15min, then air cooling. Isothermal spheroidizing annealing process: temperature 790℃, straight into the furnace for 3h, furnace cooling to 720℃ for 3h, then furnace cooling to 650℃, air cooling. Quenching temperature is 840℃, heat preservation for 30min, then oil quenching, tempering at 400℃ for 2h, air cooling to room temperature.

[0020] Then after stamping forming, surface mechanical grinding, sample A is obtained. The surface hardness of sample A is 52HRC, and the surface roughness is Ra9 microns. Sample A is placed on the selected area laser melting substrate for pre-heat preservation, the heat preservation temperature is 150℃, and the heat preservation time is 0.5h; S2, sample A is processed by using a laser beam with a size of 70 microns, and the texture pattern is set as uniform square distribution, the texture horizontal and vertical spacing is 400 microns. 100W laser power and 400mm / s scanning speed are selected for remelting processing. After laser remelting, the average diameter of the pit-shaped texture is 196 microns, the average depth is 35 microns, and the size precision of the texture point distribution is not more than 50 microns, sample B is obtained. See Figure 1 , the pit morphology is Figure 2 .

[0021] S3, sample B is annealed to remove stress, the heating temperature is 200℃, and the heat preservation time is 1h, sample C is obtained.

[0022] S4, sample C is polished on the surface, the polishing medium is diamond, the surface roughness is Ra8 microns, and finally the finished sample is obtained.

[0023] Example 2 This example is carried out on GCr15 steel substrate, and the specific preparation method is as follows: S1, GCr15 steel is heat treated, the heat treatment process is the same as example 1, and the surface of the stamping forming is shot blasted with 20S, the shot is corundum, and the coverage is 100%. After surface mechanical grinding, sample A is obtained. The surface hardness of sample A is 55HRC, and the surface roughness is Ra10 microns. Sample A is placed on the selected area laser melting substrate for pre-heat preservation, the heat preservation temperature is 200℃, and the heat preservation time is 0.5h; S2, sample A is processed by using a laser beam with a size of 100 microns, and the texture pattern is set as uniform square distribution, the texture horizontal and vertical spacing is 500 microns. 150W laser power and 300mm / s scanning speed are selected for remelting processing. After laser remelting, the average diameter of the pit-shaped texture is 311 microns, the average depth is 63 microns, and the size precision of the texture point distribution is not more than 50 microns, sample B is obtained. The pit morphology is Figure 3 .

[0024] S3. Stress-relief annealing is performed on sample B at a heating temperature of 200℃ and a holding time of 1 hour to obtain sample C.

[0025] S4. Perform surface polishing on sample C using diamond as the polishing medium, achieving a surface roughness of Ra9 micrometers, to obtain the final product sample.

[0026] Example 3 This embodiment focuses on a T10 steel substrate, and the specific preparation method is as follows: S1 and T10 steels undergo heat treatment, with the following process: 760℃, direct furnace induction and holding for 3 hours, furnace cooling to 500℃, air cooling after removal from the furnace, quenching at 780℃, holding for 40 minutes followed by oil quenching, tempering at 300℃ and holding for 2 hours, then air cooling to room temperature after removal from the furnace.

[0027] After being stamped and formed, sample A was obtained by mechanical grinding. The surface hardness of sample A was 54 HRC, and the surface roughness was Ra 8 micrometers. Sample A was placed on a selective laser melting substrate for pre-heating at 170℃ for 0.5 hours. S2. Sample A was processed using an 80-micron laser beam, with the texture pattern set as a uniform square distribution and a horizontal and vertical spacing of 700 microns. A 200W laser power and a scanning speed of 450mm / s were used for remelting. After laser remelting, the average diameter of the pit-shaped texture was 396 microns, the average depth was 76 microns, and the dimensional accuracy of the texture point distribution did not exceed 50 microns, resulting in sample B. See [link to details] for the pit morphology. Figure 4 .

[0028] S3. Stress-relief annealing is performed on sample B at a heating temperature of 250℃ and a holding time of 1 hour to obtain sample C.

[0029] S4. Perform surface polishing on sample C using diamond as the polishing medium, achieving a surface roughness of Ra9 micrometers, to obtain the final product sample.

[0030] Comparative Example To investigate the effect of microtexture on the wear resistance of the samples, samples from different embodiments were compared with those without microtexturization. The specific preparation methods were similar to those in Example 1, except that the texture patterns used were different, as detailed below: Comparative Example 1: The sample in this comparative example has only undergone heat treatment and surface treatment. The texture pattern used in Example 1 is a 5×5 pit type, and the horizontal and vertical spacing of the texture is 400 micrometers. The wear coefficient change during the friction process is as follows: Figure 5 As shown, the textured sample has a lower coefficient of friction.

[0031] Comparative Example 2: The sample of this comparative example is only heat treated and surface treated, the texture pattern used in Example 1 is 5x5 pit type, the texture horizontal and vertical distance is 500 microns, the wear coefficient change of the friction process is shown in Figure 6 It can be seen that the textured sample has a lower friction coefficient.

[0032] The present application can obtain micron-level pit texture as oil storage site in the friction process by introducing micro-texture through a simple laser remelting method, and the micro-texture pit has higher hardness due to rapid cooling, thereby realizing the improvement of wear resistance. The method is simple and easy to popularize, can be combined with various surface treatment methods at the same time, and has good practical value.

[0033] The specific advantages are as follows: 1. Only remelting is used, no additional materials are needed, the preparation method is simple, the process is easy to control, and it can be applied to large-scale industrial production and popularization.

[0034] 2. The surface prepared by remelting plays a dual role of introducing hard texture and pit morphology due to the rapid solidification of the small molten pool, a better oil film layer is obtained, and the wear resistance is improved.

[0035] 3. The method is suitable for various substrate materials and can be easily combined with different surface treatments, and has a wide range of applications.

[0036] 4. The prepared sample has better wear resistance than the untextured sample, and the service life of the sample is improved.

Claims

1. A method for improving the surface wear resistance of a steel distribution plate by laser 3D printing and remelting texture, characterized in that, Follow these steps in sequence: S1. Place the heat-treated, stamped, and surface-grinded distribution plate sample on the selective laser melting substrate for preheating. S2. Perform laser remelting scanning according to the set texture pattern to obtain a sample with a microtexture pattern; S3. Perform stress-relief annealing on the microtextured pattern sample; S4. The stress-relief annealed sample is then polished to obtain the final product sample.

2. The method according to claim 1, characterized in that, In step S1, the heat treatment includes one or more of quenching, tempering and / or surface carburizing, nitriding, shot peening, and hot and cold spraying, and the surface layer hardness is 50-55HRC.

3. The method according to claim 1, characterized in that, In step S1, the surface roughness after surface grinding does not exceed Ra10 micrometers.

4. The method according to claim 1, characterized in that, In step S1, the pre-insulation temperature is 150-200℃, and the insulation time is 0.5-1 hour.

5. The method according to claim 1, characterized in that, In step S2, the size of the laser beam during the laser remelting process is 60-100 micrometers.

6. The method according to claim 1, characterized in that, In step S2, the laser power of the laser remelting is 100-250W, and the scanning speed is 200-500mm / s.

7. The method according to claim 1, characterized in that, In step S2, the microtexture formed after laser remelting is pit-shaped, with a diameter of 150-400 micrometers and a depth of 30-100 micrometers. The dimensional accuracy of the texture point distribution does not exceed 50 micrometers.

8. The method according to claim 1, characterized in that, In step S3, the stress-relief annealing is carried out in a vacuum heat treatment furnace, with a heating temperature of 200-350℃ and a holding time of 1-2 hours.

9. The method according to claim 1, characterized in that, In step S4, the surface roughness after the surface polishing treatment is Ra10 micrometers.

10. The method according to claim 1, characterized in that, In step S2, the texture pattern is a uniformly square distribution.

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