Preparation method of high-hardness wear-resistant coating on surface of coal mine mechanical equipment

Abstract

The invention relates to the technical field of products made of metal powder, in particular to a preparation method of a high-hardness wear-resistant coating on the surface of coal mine mechanical equipment. Comprising the following steps: S1, pretreatment; s2, powder pre-alloying is carried out; and S3, laser cladding. A specific mechanical alloying process, a cladding powder formula and a high-speed laser cladding modification process are adopted, the high-hardness wear-resistant coating which is compact in structure and is in high metallurgical bonding with a matrix is prepared on the surface of the 27SiMn steel, the hardness and wear resistance of the 27SiMn steel can be remarkably improved, the service life of the 27SiMn steel is prolonged, and the service life of the 27SiMn steel is prolonged. And the method has the advantages of simple process, environmental friendliness and high repeatability, thereby having favorable engineering practical value.

Description

Technical Field

[0001] The invention relates to the technical field of products made from metal powder, and in particular to a method for preparing a high-hardness wear-resistant coating on the surface of coal mine mechanical equipment. Background Art

[0002] 27SiMn steel has high strength and toughness, excellent wear resistance and good machining performance and is widely used in heavy-duty machinery, automobile suspension systems, petrochemicals, bridge construction and other fields. However, when 27SiMn is used as the shutdown structural material of the "three machines and one frame" (coal mining machine, tunneling machine, scraper conveyor and hydraulic support) of coal mine comprehensive mining equipment, it is very easy to fail due to wear and tear due to frequent impact and wear of slag, gangue, etc. during operation, resulting in frequent equipment shutdowns, which not only greatly reduces the reliability of the equipment and poses serious safety hazards, but also reduces the production efficiency of the enterprise and increases operating costs.

[0003] The use of surface modification technology to prepare a protective layer with specific properties can improve its practicality without changing the properties of the material matrix. The method is convenient, economical and environmentally friendly, and is an effective way to improve the wear resistance of 27SiMn. Domestic and foreign scholars have done a lot of research on this and have achieved good results. Various protective coating systems have been prepared using various technologies or composite technologies such as surfacing technology, electroplating technology, micro-arc oxidation technology, thermal spraying technology, and vapor deposition technology, and have achieved relatively good results in improving the wear resistance of 27SiMn, but there are still some problems. For example, there are many defects such as pores, cracks and burns in the coating prepared by surfacing technology; the coating prepared by electroplating technology is thin, has poor bonding with the substrate, and is prone to large-scale peeling during use, and the electroplating waste liquid is highly toxic and environmentally unfriendly; the film layer prepared by micro-arc oxidation and thermal spraying technology has excellent performance and good bonding with the substrate, but the process is complicated and the preparation cost is high, which is not conducive to large-scale use; the coating prepared by vapor deposition technology is thin and prone to wear-through failure, which is not suitable for actual industrial production. In summary, the present application now proposes a method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment to solve the above problems. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment.

[0005] The technical solution of the present invention is: a method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment, comprising the following steps:

[0006] S1. Preprocessing

[0007] Pre-treating the surface of 27SiMn steel to obtain pre-treated 27SiMn steel;

[0008] S2. Powder pre-alloying

[0009] Prepare 5-15wt% TiB 2 powder, 1-10wt% h-BN powder, 1-5wt% La 2 O 3 The powder and the remaining FZC213 iron-based powder are placed in a planetary ball mill and ball-milled at a speed of 400 to 800 r / min for 10 to 20 hours to pre-alloy the powder;

[0010] S3, Laser Cladding

[0011] The pre-alloyed powder is placed in a coaxial powder device of a laser cladding device, clad on the surface of the pretreated 27SiMn steel under a protective atmosphere, and air-cooled to room temperature after cladding to obtain a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment.

[0012] Furthermore, the parameters of the laser cladding equipment are: laser cladding power: 2-3KW; spot diameter: 3-8mm; scanning speed: 5-10mm·s -1 ; Overlap rate: 30-50%; Powder feeding speed: 8-16g·r -1 ;

[0013] Note: By reasonably controlling the value range of the above parameters, the powder can absorb the laser beam energy more efficiently, improve the laser cladding efficiency, and achieve good metallurgical bonding between the cladding layer and the substrate layer.

[0014] Furthermore, the TiB 2 powder, h-BN powder, La 2 O 3 The particle size of powder and FZC213 iron-based powder is 200 mesh;

[0015] Description: After repeated tests and verification, the use of 200 mesh powder can be better distributed on the surface of the base material during cladding, forming a more uniform and dense cladding layer. At the same time, it can be fully melted and solidified during cladding, reducing defects such as cracks and holes, and further improving the quality of the cladding layer.

[0016] Furthermore, the protective atmosphere is Ar gas with a purity of 99% and a flow rate of 10 to 15 L / min;

[0017] Note: Appropriate gas flow rate helps to evenly transport powder to the cladding area, ensuring the utilization of powder and the uniformity of the cladding layer, thereby improving the bonding strength and surface finish of the cladding layer; appropriate gas flow rate also helps to improve the utilization of laser, reduce the obstruction of metal vapor or plasma cloud to laser penetration, thereby improving cladding efficiency; by controlling the flow rate of argon gas, it is possible to reduce spatter and pores generated during welding, improve the morphology and density of the weld, and thus improve the overall performance of the cladding layer.

[0018] Further, the FZC213 iron-based powder comprises, by mass percentage, 7.0-21.0wt% of Cr, 5.1-8.2wt% of Ni, 0.12-0.18wt% of Mn, 1.1-1.6wt% of Mo, 0.10-0.15wt% of Co, 0.5-0.9wt% of Si, 0.1-0.2wt% of C, and the balance of Fe;

[0019] Description: The components of FZC213 iron-based powder include Fe, Cr, Ni, Mn, Mo, Co, Si, and C. After the powder is prepared, it is clad on the surface of 27SiMn. The cladding layer is composed of γ-Fe, Fe-Ni solid solution, Fe 3 Ni 2 The phase mainly consists of Cr-Ni-Fe-C, Fe 3 Ni 2 The wear resistance of Cr-Ni-Fe-C is good, and the TiB added in the cladding layer 2 Can enhance wear resistance, self-lubricating property of h-BN and CeO 2 The grain refinement effect makes the coating highly hard and wear-resistant.

[0020] Further, the cladding method described in S3 is a gradient cladding treatment, specifically: the pretreated 27SiMn steel is placed horizontally with the processing surface facing upward, the length of the pretreated 27SiMn steel is recorded as L, the center of the pretreated 27SiMn steel is taken as a reference point, 0.3 to 0.5L of the total length is extended on both sides of the length direction and recorded as the first cladding layer, and then 0.15 to 0.35L are extended along both sides of the first cladding layer as the second cladding layer, and the remaining part is the third cladding layer;

[0021] The thickness of the first cladding layer is 2.5-3 mm, the longitudinal section of the second cladding layer is a trapezoidal structure, and the long side of the trapezoidal structure is adjacent to the first cladding layer, the short side of the trapezoidal structure is 1-1.5 mm thick, and the longitudinal section of the third cladding layer is a triangular structure, and the side of the triangular structure is adjacent to the second cladding layer;

[0022] Note: The setting of thick center and thin sides is because the stress distribution is uneven at the interface between the coating and the substrate, with relatively large stress in the center and relatively small stress at the edge. The above setting can make the stress distribution more uniform, reduce stress concentration, thereby improving the bonding strength and stability of the coating, and can also make the coating better adapt to this uneven wear mode during the wear process, extending the service life of the coating.

[0023] Furthermore, each cladding layer after the gradient cladding treatment is subjected to an anti-stripping treatment, and the anti-stripping treatment comprises the following steps: a heat-insulating layer is provided for the portion other than the adjacent portion of each cladding layer after air cooling to 25-30°C, and then the cladding layer is placed in a hot isostatic pressing device, and the adjacent portion of each cladding layer is kept warm for 3-10 minutes under a pressure of 50-80 MPa, and the heat-insulating layer is removed after the heat-insulating is completed, and each cladding layer is cooled to 20-35°C, and then treated for 25-40 minutes at a magnetic field strength of 0.6-0.8T and a pulse frequency of 1-3 Hz;

[0024] Description: Hot isostatic pressing can eliminate defects at the joints of the cladding layer and improve the density of the coating at the joints, while pulsed magnetic field treatment can further improve the microstructure of the coating and enhance its anti-stripping ability. In the gradient coating on the steel surface, pulsed magnetic field treatment can improve the anti-stripping ability of the coating by changing the crystal structure and stress distribution inside the coating.

[0025] Further, the pretreatment method is: using an angle grinder to grind and polish the surface of 27SiMn steel to remove the surface oxide layer and impurities, and then using 400-1500# SiC sandpaper to polish it step by step; placing the polished 27SiMn steel in alcohol for ultrasonic cleaning for 8-12 minutes; finally placing the ultrasonically cleaned 27SiMn steel in a dryer and drying it at 190-210°C for 25-35 minutes;

[0026] Note: The purpose of the above pretreatment method is to completely clean the surface, avoid contamination of 27SiMn steel, affect the bonding between the coating and the substrate, ensure the quality of the coating, and lay a good foundation for further cladding coating on the surface of 27SiMn steel.

[0027] Furthermore, the rotation speed of the angle grinder is 5000-5600 r / min, the grinding and polishing time is 5-7 min, the feed speed is 5-10 mm / min, and the ultrasonic power is 20-40 W / cm 2 ;

[0028] Note: Reasonable control of the numerical range of the above parameters can effectively clean the sample surface.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention adopts a specific mechanical alloying process, a cladding powder formula and a high-speed laser cladding modification process to prepare a high-hardness and wear-resistant coating with a dense structure and a high metallurgical bond with the substrate on the surface of 27SiMn steel. The coating can significantly improve the hardness and wear resistance of 27SiMn steel and extend its service life. It also has the advantages of simple process, environmental friendliness and strong repeatability, and thus has good engineering practical value.

[0031] (2) The present invention adopts gradient cladding treatment and adopts a cladding layer with a thick center and thin sides, so that the hardness and wear resistance of the coating are significantly improved, the influence of uneven stress distribution at the interface between the coating and the 27SiMn steel substrate is reduced, and stress concentration is reduced, thereby improving the bonding strength and stability of the coating, and also enabling the coating to better adapt to this uneven wear mode during the wear process, thereby extending the service life of the coating.

[0032] (3) The present invention provides a heat-insulating layer in the part other than the adjacent part of the cladding layer, and then performs hot isostatic pressing and magnetic field pulse treatment to achieve anti-stripping treatment of the cladding layer, which can effectively prevent the coating from peeling off when it is worn and improve the service life of the high-hardness and wear-resistant coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate one or more embodiments of the present specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or more embodiments of the present specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a metallographic surface morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4;

[0035] Figure 2 is a metallographic surface morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1;

[0036] Figure 3 This is a metallographic surface morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5;

[0037] Figure 4 This is the overall SEM morphology of the cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4;

[0038] Figure 5 This is a cross-sectional overall SEM morphology of the high-hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1;

[0039] Figure 6 This is the overall SEM morphology of the cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5;

[0040] Figure 7 This is a SEM morphology of the upper cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4;

[0041] Figure 8 This is a SEM morphology of the middle section of the high hardness and wear resistant coating on the surface of 27SiMn steel obtained in Example 4;

[0042] Fig. 9 This is a SEM morphology of the lower cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4;

[0043] Fig.10 This is a SEM morphology of the upper cross-section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1;

[0044] Fig.11 This is a SEM morphology of the middle section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1;

[0045] Fig.12 This is a SEM morphology of the lower part of the cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1;

[0046] Fig.13 This is a SEM morphology of the upper cross-section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5;

[0047] Fig.14 This is a SEM morphology of the middle section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5;

[0048] Fig.15 This is a SEM morphology of the lower part of the cross section of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5;

[0049] Fig.16 1 is a microhardness distribution diagram of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1, Example 4 and Example 5 along the cross section;

[0050] Fig.17 1 is a friction coefficient curve of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1, Example 4 and Example 5;

[0051] Fig.18 This is a SEM morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Comparative Example 0 after being worn for 20 minutes under a load of 30N;

[0052] Fig.19 This is a SEM morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4 after being worn for 20 minutes under a load of 30N;

[0053] Fig. 20 This is a SEM morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1 after being worn for 20 minutes under a load of 30N;

[0054] Fig.21 This is a SEM morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5 after being worn for 20 minutes under a load of 30N;

[0055] Fig. 22 This is a three-dimensional white light topography image of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in comparative example 0 after being worn for 20 minutes under a load of 30N;

[0056] Fig.23 This is a three-dimensional white light topography of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 4 after being worn for 20 minutes under a load of 30N;

[0057] Fig.24 This is a three-dimensional white light topography of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 1 after being worn for 20 minutes under a load of 30N;

[0058] Fig.25 This is a three-dimensional white light topography of the high hardness and wear-resistant coating on the surface of 27SiMn steel obtained in Example 5 after being worn for 20 minutes under a load of 30N;

[0059] Fig.26 It is a schematic diagram of gradient cladding on the surface of 27SiMn steel. DETAILED DESCRIPTION

[0060] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0061] Example 1: A method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment, comprising the following steps:

[0062] S1. Preprocessing

[0063] The surface of 27SiMn steel was pretreated to obtain pretreated 27SiMn steel; the pretreatment method was: using an angle grinder at a speed of 5300 r / min, a grinding and polishing time of 6 min, a feed speed of 8 mm / min, and an ultrasonic power of 30 W / cm 2The surface of 27SiMn steel was ground and polished under the conditions to remove the surface oxide layer and impurities, and then 400-1500# SiC sandpaper was used to polish it step by step; the polished 27SiMn steel was ultrasonically cleaned in alcohol for 10 minutes; finally, the ultrasonically cleaned 27SiMn steel was placed in a dryer and dried at 200℃ for 30 minutes;

[0064] S2. Powder pre-alloying

[0065] Preparation of 10wt% TiB 2 powder, 5wt% h-BN powder, 3wt% La 2 O 3 The powder and the remaining FZC213 iron-based powder were placed in a planetary ball mill and ball-milled at a speed of 600 r / min for 15 h to pre-alloy the powder; TiB 2 powder, h-BN powder, La 2 O 3 The particle size of powder and FZC213 iron-based powder is 200 mesh;

[0066] The FZC213 iron-based powder comprises, by mass percentage, 19wt% Cr, 6.5wt% Ni, 0.14wt% Mn, 1.4wt% Mo, 0.13wt% Co, 0.7wt% Si, 0.15wt% C, and the balance Fe;

[0067] S3, Laser Cladding

[0068] The pre-alloyed powder is placed in the coaxial powder feeding device of the laser cladding equipment, and clad on the pre-treated 27SiMn steel surface under a protective atmosphere. After cladding, it is air-cooled to room temperature to obtain a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment; the protective atmosphere is 99% pure Ar gas with a flow rate of 12L / min;

[0069] The parameters of the laser cladding equipment are: laser cladding power: 2.5KW; spot diameter 6mm; scanning speed: 8mm·s -1 ; Overlap rate: 40%; Powder feeding speed: 12g·r -1 ; The coaxial powder feeding device is a powder feeding device in the prior art;

[0070] The cladding method in this embodiment is to use laser cladding equipment for conventional cladding, that is, the coating after cladding has a uniform thickness, and the thickness is limited to 2 mm in this embodiment.

[0071] Embodiment 2: Different from Embodiment 1, the pretreatment method is: using an angle grinder at a speed of 5000 r / min, a grinding and polishing time of 5 min, a feed speed of 5 mm / min, and an ultrasonic power of 20 W / cm 2The surface of 27SiMn steel was ground and polished under the conditions to remove the surface oxide layer and impurities, and then 400-1500# SiC sandpaper was used to polish it smooth step by step; the polished 27SiMn steel was ultrasonically cleaned in alcohol for 8 minutes; finally, the ultrasonically cleaned 27SiMn steel was placed in a dryer and dried at 190°C for 25 minutes.

[0072] Embodiment 3: Different from Embodiment 1, the pretreatment method is: using an angle grinder at a speed of 5600 r / min, a grinding and polishing time of 7 min, a feed speed of 10 mm / min, and an ultrasonic power of 40 W / cm 2 The surface of 27SiMn steel was ground and polished under the conditions to remove the surface oxide layer and impurities, and then 400-1500# SiC sandpaper was used to polish it smooth step by step; the polished 27SiMn steel was ultrasonically cleaned in alcohol for 12 minutes; finally, the ultrasonically cleaned 27SiMn steel was placed in a dryer and dried at 210℃ for 35 minutes.

[0073] Example 4: Different from Example 1, in S2, 5 wt% TiB is prepared 2 powder, 1wt% h-BN powder, 1wt% La 2 O 3 The powder and the remaining FZC213 iron-based powder are placed in a planetary ball mill and ball-milled at a rotation speed of 400 r / min for 10 h to pre-alloy the powder.

[0074] Example 5: Different from Example 1, in S2, 15wt% TiB is prepared 2 powder, 10wt% h-BN powder, 5wt% La 2 O 3 The powder and the remaining FZC213 iron-based powder are placed in a planetary ball mill and ball-milled at a rotation speed of 800 r / min for 20 h to pre-alloy the powder.

[0075] Example 6: Different from Example 1, in S2, the FZC213 iron-based powder includes, by mass percentage, 19.86wt% Cr, 6.121wt% Ni, 0.157wt% Mn, 1.385wt% Mo, 0.125wt% Co, 0.788wt% Si, 0.12wt% C, and the remainder Fe.

[0076] Example 7: Different from Example 1, in S2, the FZC213 iron-based powder includes, by mass percentage, 17.54wt% Cr, 7.72wt% Ni, 0.136wt% Mn, 1.42wt% Mo, 0.14wt% Co, 0.63wt% Si, 0.15wt% C, and the remainder Fe.

[0077] Embodiment 8: Different from Embodiment 1, in S3, the protective atmosphere flow rate is 10 L / min.

[0078] Embodiment 9: Different from Embodiment 1, in S3, the protective atmosphere flow rate is 15 L / min.

[0079] Example 10: Different from Example 1, in S3, the parameters of the laser cladding equipment are: laser cladding power: 2KW; spot diameter: 3mm; scanning speed: 5mm·s -1 ; Overlap rate: 30%; Powder feeding speed: 8g·r -1 .

[0080] Example 11: Different from Example 1, in S3, the parameters of the laser cladding equipment are: laser cladding power: 3KW; spot diameter: 8mm; scanning speed: 10mm·s -1 ; Overlap rate: 50%; Powder feeding speed: 16g·r -1 .

[0081] Example 12: Different from Example 1, the cladding method of S3 is a gradient cladding treatment, specifically: the pretreated 27SiMn steel is placed horizontally with the processing surface facing upward, the length of the pretreated 27SiMn steel is denoted as L, the center of the pretreated 27SiMn steel is taken as a reference point, 0.4L is extended along the length direction on both sides thereof and recorded as the first cladding layer, and then 0.25L is extended along both sides of the first cladding layer as the second cladding layer, and the remaining part is the third cladding layer;

[0082] The thickness of the first cladding layer is 2.8 mm, the longitudinal section of the second cladding layer is a trapezoidal structure, and the long side of the trapezoidal structure is adjacent to the first cladding layer, the short side of the trapezoidal structure is 1.3 mm thick, and the longitudinal section of the third cladding layer is a triangular structure, and the side of the triangular structure is adjacent to the second cladding layer.

[0083] Example 13: Different from Example 12, the center of the pretreated 27SiMn steel is taken as the reference point, 0.3L is extended along the length direction on both sides thereof and recorded as the first cladding layer, and then 0.15L is extended along both sides of the first cladding layer as the second cladding layer, and the remaining part is the third cladding layer;

[0084] The thickness of the first cladding layer is 2.5 mm, the longitudinal section of the second cladding layer is a trapezoidal structure, and the long side of the trapezoidal structure is adjacent to the first cladding layer, the short side of the trapezoidal structure is 1 mm thick, and the longitudinal section of the third cladding layer is a triangular structure, and the side of the triangular structure is adjacent to the second cladding layer.

[0085] Example 14: Different from Example 12, the center of the pretreated 27SiMn steel is taken as the reference point, 0.5L is extended on both sides along the length direction and recorded as the first cladding layer, and then 0.35L is extended on both sides of the first cladding layer as the second cladding layer, and the remaining part is the third cladding layer;

[0086] The thickness of the first cladding layer is 3 mm, the longitudinal section of the second cladding layer is a trapezoidal structure, and the long side of the trapezoidal structure is adjacent to the first cladding layer, the short side of the trapezoidal structure is 1.5 mm thick, and the longitudinal section of the third cladding layer is a triangular structure, and the side of the triangular structure is adjacent to the second cladding layer.

[0087] Example 15: Different from Example 12, an insulating layer is set on the part other than the adjacent parts of each cladding layer after air cooling to 27°C, and then it is placed in a hot isostatic pressing equipment, and the adjacent parts of each cladding layer are kept warm for 6 minutes under a pressure of 65MPa. After the insulation is completed, the insulating layer is removed, and after each cladding layer is cooled to 28°C, it is treated for 32 minutes at a magnetic field intensity of 0.7T and a pulse frequency of 2HZ.

[0088] Example 16: Different from Example 15, an insulating layer is provided for the portion other than the adjacent portion of each cladding layer after air cooling to 25°C, and then it is placed in a hot isostatic pressing device, and the adjacent portion of each cladding layer is kept warm for 3 minutes under a pressure of 50 MPa. After the insulation is completed, the insulating layer is removed, and after each cladding layer is cooled to 20°C, it is treated for 25 minutes at a magnetic field strength of 0.6 T and a pulse frequency of 1 Hz to achieve anti-peeling treatment of the cladding layer.

[0089] Example 17: Different from Example 15, an insulating layer is provided for the portion other than the adjacent portion of each cladding layer after air cooling to 30°C, and then it is placed in a hot isostatic pressing device, and the adjacent portion of each cladding layer is kept warm for 10 minutes under a pressure of 80 MPa. After the insulation is completed, the insulating layer is removed, and after each cladding layer is cooled to 35°C, it is treated for 40 minutes at a magnetic field strength of 0.8 T and a pulse frequency of 3 Hz to achieve anti-peeling treatment of the cladding layer.

[0090] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and is intended to illustrate the practical application effect of the present invention.

[0091] like Figure 1-Figure 3As shown, the surface morphologies of the composite gradient coatings obtained under different process conditions in Example 1, Example 4 and Example 5 are compared. Figure 1 The coating shown is prepared in Example 4. Figure 2 The coating shown is prepared in Example 1. Figure 3 The coating shown is prepared in Example 5. It can be seen that the coating prepared in Example 1 has the finest surface dendrite structure.

[0092] like Figure 4-Figure 15 As shown, the microscopic morphology of the cross section of the high hardness and wear-resistant coating obtained under different process conditions in Example 1, Example 4 and Example 5 are compared. Figure 4 and Figure 7 to Figure 9 The coating shown is a SEM morphology of the entire cross section and the upper, middle and lower parts of the cross section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel prepared in Example 4. Figure 5 and Figure 10 to Figure 12 The coating shown is a SEM morphology of the entire cross section and the upper, middle and lower parts of the cross section of the high-hardness and wear-resistant coating on the surface of 27SiMn steel prepared in Example 1. Figure 6 and Figure 13 to Figure 15 The coating shown is the SEM morphology of the whole cross section and the upper, middle and lower parts of the cross section of the high hardness and wear resistant coating on the surface of 27SiMn steel prepared in Example 5. It can be seen that the prepared coatings are composed of fine equiaxed crystals in the upper part, relatively coarse equiaxed crystals in the middle part and coarse columnar crystals perpendicular to the surface of the pattern at the bottom, among which the high hardness and wear resistant coating prepared in Example 1 has a moderate thickness, and the organizational structure of the upper, middle and lower parts is denser than that of the other two examples, and the size of the dendrite and eutectic organization is smaller.

[0093] Fig.16 , Fig.17 The microhardness distribution along the cross section and the friction coefficient curves of the high hardness and wear-resistant coating samples on the surface of 27SiMn steel obtained in Example 1, Example 4 and Example 5 respectively under a reciprocating friction load of 30N. Among them, the high hardness and wear-resistant coating prepared in Example 1 has the highest hardness and the friction coefficient is at the lowest level.

[0094] Figure 18-Figure 25 middle, Fig.19 and Fig.23 The SEM morphology and three-dimensional white light morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel prepared in Example 4 after reciprocating wear for 20 minutes under a load of 30N; Fig. 20 and Fig.24 The SEM morphology and three-dimensional white light morphology of the high-hardness and wear-resistant coating on the surface of 27SiMn steel prepared in Example 1 after reciprocating wear for 20 minutes under a load of 30N; Fig.21 and Fig.25The SEM morphology and three-dimensional white light morphology of the high hardness and wear-resistant coating on the surface of 27SiMn steel prepared in Example 5 after reciprocating wear for 20 minutes under a load of 30N. It can be seen that compared with Examples 4 and 5, the high hardness and wear-resistant coating prepared in Example 1 has the smallest wear width and depth.

[0095] Sample performance test

[0096] 1. The high-hardness wear-resistant coatings obtained by the methods described in Examples 1 to 3 were subjected to friction and wear tests. Comparative Example 0 was a 27SiMn substrate with an untreated surface, and a friction and wear test was performed under a load of 30N.

[0097] The wear rate results are shown in the following table:

[0098] Table 1 Friction and wear conditions of the high-hardness and wear-resistant coatings obtained in Example 1, Examples 4 to 5 and Comparative Example 0.

[0099]

[0100] 2. Wear resistance test: The actual performance of the present invention under different experimental conditions was compared. The specific data are shown in Table 2.

[0101] Table 2 Friction and wear of high hardness and wear-resistant coatings obtained in Examples 1 to 3, Examples 6 to 17 and Control Groups 1 to 2

[0102]

[0103] Conclusion: From the data of Examples 1 to 11 in Table 1 and Table 2, it can be seen that the friction and wear of the high-hardness wear-resistant coating obtained in Example 1 is better, while the changes in the parameters in Examples 2 to 11 will cause the wear of the high-hardness wear-resistant coating to become more serious. This experimental example compares the morphology of Examples 1 and Examples 4 to 5. The results are as follows: Figure 1 to Figure 7As shown, therefore, Example 1 is selected as the optimal solution. By comparing Example 1 and Examples 12 to 14, it can be seen that Examples 12 to 14 perform gradient cladding, which can effectively improve the wear resistance of the coating, and taking Example 12 into consideration, the optimal solution is obtained. The reason for the above results may be that the cladding layer is thick in the center and thin on both sides. The main reason for the above setting is that the stress distribution at the interface between the coating and the substrate is uneven, the stress in the center is relatively large, and the stress in the edge is relatively small. Gradient cladding can make the stress distribution more uniform, reduce stress concentration, thereby improving the bonding strength and stability of the coating, and can also make the coating better adapt to this uneven wear mode during the wear process, thereby extending the service life of the coating. From the comparison of Example 12 and Example 15 to Example 17, it can be seen that the subsequent anti-stripping treatment also has a great effect on improving the wear resistance of the high-hardness wear-resistant coating. This is mainly because hot isostatic pressing can be used to eliminate defects inside the coating and improve the density and mechanical properties of the material, while pulsed magnetic field treatment can improve its anti-stripping performance by changing the microstructure of the material, thereby improving the hardness and wear resistance of the coating. From the comparison of Example 15 to Example 17, it can be seen that setting the insulating protective layer at the part other than the adjacent part can effectively improve the hardness and wear resistance of the coating. This is because when an insulating and heat-preserving layer is set at the part other than the adjacent part of the cladding layer after air cooling to 25 to 30°C and subsequent hot isostatic pressing treatment is performed, the overall cooling rate of the cladding layer is controlled except for the adjacent part. This control helps to maintain the phase structure formed by the cladding layer at high temperature and reduce the internal stress caused by too rapid cooling. The stability of the phase structure helps to maintain the high hardness of the cladding layer, because many high-hardness phases (such as some metal carbides, etc.) are formed and stably exist at specific temperatures and pressures. If the cooling rate is too fast, these phases may change or produce defects, thereby reducing the hardness. In the magnetic field and pulse treatment stage, due to the relatively stable structure of the early cladding layer, the internal microstructure can be adjusted more orderly under the action of the magnetic field and pulse. For example, magnetic treatment may make the orientation of some magnetic phases more conducive to resisting external forces, thereby improving the overall hardness; during the hot isostatic pressing process, the insulation treatment of the adjacent parts of the cladding layer (except for the adjacent parts, there is an insulating layer) can reduce defects such as microcracks inside the cladding layer. The reduction of microcracks means that when subjected to wear stress, the cladding layer is not prone to severe wear such as peeling, thereby improving wear resistance. After the magnetic field and pulse treatment, the microstructure of the cladding layer is more uniform, further improving its wear resistance.

[0104] From the comparison of Examples 15 to 17 and Control Groups 1 to 2, it can be seen that setting the thermal insulation protective layer at the adjacent part or not setting the thermal insulation protective layer will make the overall performance of the cladding layer worse. If the thermal insulation layer is set at the joint, the temperature and pressure environment of the joint will be different from other parts during the hot isostatic pressing process. Due to the setting of the insulation layer, the heat loss at the joint is slower, which may cause the diffusion and phase transformation of local elements to be inconsistent with other parts. This inconsistency may form a special phase structure at the joint, which may increase the local hardness. For example, some elements diffuse to the joint at high temperature and form a strengthening phase, which enhances the hardness of the joint. However, if this phase structure does not match the overall phase structure of the cladding layer, a hardness gradient may be formed at the joint, affecting the overall uniformity; and the special phase structure and hardness change at the joint may cause the wear behavior of the joint and other parts of the cladding layer to be inconsistent during the wear process. If the hardness of the joint is too high and is not well combined with other parts, peeling may occur first during the wear process, thereby reducing the overall wear resistance. The lack of thermal insulation layer will affect the uniformity of the cladding layer during the hot isostatic pressing process. The wear resistance is often related to the microstructure of the cladding layer. The uneven structure will cause the cladding layer to wear rapidly locally during the wear process. In addition, without the thermal insulation layer, the overall temperature of the cladding layer may not reach the ideal uniformity, which may lead to uneven growth of the crystal structure inside the cladding layer, thereby reducing the hardness of the coating.

[0105] In summary, Example 15 is selected as the optimal solution.

Claims

1. A method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment, characterized in that: The steps include: S1. Preprocessing Pre-treating the surface of 27SiMn steel to obtain pre-treated 27SiMn steel; S2. Powder pre-alloying 5-15wt% TiB2 powder, 1-10wt% h-BN powder, 1-5wt% La2O3 powder and the rest FZC213 iron-based powder are prepared and placed in a planetary ball mill, and ball milled at a speed of 400-800r / min for 10-20h to pre-alloy the powder; S3, Laser Cladding The pre-alloyed powder is placed in a coaxial powder device of a laser cladding device, clad on the surface of the pretreated 27SiMn steel under a protective atmosphere, and air-cooled to room temperature after cladding to obtain a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment.

2. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The parameters of the laser cladding equipment are: laser cladding power: 2-3KW; spot diameter: 3-8mm; scanning speed: 5-10mm / s; overlap rate: 30-50%; powder feeding speed: 8-16g / r.

3. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The particle sizes of the TiB2 powder, h-BN powder, La2O3 powder and FZC213 iron-based powder are all 200 meshes.

4. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The protective atmosphere is Ar gas with a purity of 99% and a flow rate of 10 to 15 L / min.

5. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The FZC213 iron-based powder includes, by mass percentage, 17.0-21.0wt% of Cr, 5.1-8.2wt% of Ni, 0.12-0.18wt% of Mn, 1.1-1.6wt% of Mo, 0.10-0.15wt% of Co, 0.5-0.9wt% of Si, 0.1-0.2wt% of C, and the balance of Fe.

6. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The cladding method described in S3 is a gradient cladding treatment, specifically: the pre-treated 27SiMn steel is placed horizontally with the processing surface facing upward, the length of the pre-treated 27SiMn steel is recorded as L, the center of the pre-treated 27SiMn steel is taken as a reference point, 0.3 to 0.5L is extended along the length direction of both sides thereof as the first cladding layer, and then 0.15 to 0.35L is extended along both sides of the first cladding layer as the second cladding layer, and the remaining part is the third cladding layer; The thickness of the first cladding layer is 2.5 to 3 mm, the longitudinal section of the second cladding layer is a trapezoidal structure, and the long side of the trapezoidal structure is adjacent to the first cladding layer, the thickness of the short side of the trapezoidal structure is 1 to 1.5 mm, and the longitudinal section of the third cladding layer is a triangular structure, and the side of the triangular structure is adjacent to the second cladding layer.

7. The method for preparing a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 6, characterized in that: The anti-stripping treatment is performed on each cladding layer after the gradient cladding treatment. The steps of the anti-stripping treatment are as follows: an insulating layer is set on the part other than the adjacent part of each cladding layer after air cooling to 25-30°C, and then it is placed in a hot isostatic pressing device, and the adjacent part of each cladding layer is kept warm for 3-10 minutes under a pressure of 50-80MPa. After the insulation is completed, the insulating layer is removed, and each cladding layer is cooled to 20-35°C, and then treated for 25-40 minutes at a magnetic field strength of 0.6-0.8T and a pulse frequency of 1-3HZ.

8. A method for forming a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment according to claim 1, characterized in that: The pretreatment method is as follows: using an angle grinder to grind and polish the surface of 27SiMn steel to remove the surface oxide layer and impurities, and then using 400-1500# SiC sandpaper to polish it step by step; placing the polished 27SiMn steel in alcohol for ultrasonic cleaning for 8-12 minutes; finally placing the ultrasonically cleaned 27SiMn steel in a dryer for drying at 190-210°C for 25-35 minutes.

9. A method for forming a high-hardness wear-resistant coating on the surface of coal mining machinery and equipment as claimed in claim 8, characterized in that: The rotation speed of the angle grinder is 5000-5600 r / min, the grinding and polishing time is 5-7 min, the feed speed is 5-10 mm / min, and the ultrasonic power is 20-40 W / cm 2 .

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