A method for preparing a plasma sprayed / remelted diamond-ni-based wear-resistant coating

Abstract

The application discloses a preparation method of a plasma spraying / remelting diamond-Ni-based wear-resistant coating, and belongs to the technical field of wear-resistant coating preparation, and comprises the following five steps of metal alloy powder selection, preparation of Cr-plated diamond, batching, plasma spraying for preparing the wear-resistant coating and high-frequency induction remelting treatment. The characteristic technical process for preparing the diamond wear-resistant coating is developed by combining material properties and process methods, and provides a new engineering technical route for improving the wear resistance of the coating by using the diamond as super wear-resistant hard phases.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation of wear-resistant coating, and particularly relates to a method for preparing a wear-resistant coating by using plasma spraying / high-frequency induction remelting process combination to coat composite functional powder on the surface of a metal part. Cr ) as a hard phase to prepare a coating composite functional powder, and using plasma spraying / high-frequency induction remelting process combination to coat the composite functional powder on the surface of a metal part to prepare a wear-resistant coating. BACKGROUND

[0002] With the rapid development of large-scale / automation / intelligent equipment, the requirement for the wear resistance of key parts of equipment is higher and higher, especially the engineering machinery parts of mine machinery, coal machinery, petroleum equipment and the like which operate in harsh environments must withstand extreme load, severe impact, strong wear and the like. In order to improve the surface wear resistance of workpieces, surface hardening treatment technologies such as laser cladding and plasma spraying are often used to coat a certain thickness of hard wear-resistant layer on the surface of metal parts. Plasma spraying is to use a plasma arc as a heat source to make the surface of sprayed hard metal or ceramic powder partially melt, and use a high-speed ion flow to spray the powder particles to the surface of a workpiece to form a wear-resistant coating. However, since the interface bonding between the sprayed powder particles of the plasma sprayed coating is formed by condensation and connection of the surface partial melting area, there are some weaknesses: 1) the interface bonding strength between the coating powder and the workpiece substrate is low; 2) the interface bonding strength between the powder particles is low, especially the bonding strength between heterogeneous materials such as metal and ceramic is lower; 3) the coating density is insufficient, the strength is low, and there are many micro defects such as pores and cracks; 4) the interlayer bonding strength is low when multi-layer spraying; 5) the internal residual stress of the coating is too large, which easily leads to peeling, peeling and the like of the coating under the action of dynamic load. The above problems weaken the bonding strength of the coating, which greatly affects the application efficiency of plasma spraying. Therefore, how to improve the bonding strength between the plasma sprayed coating and the workpiece substrate metal, between the coating powder particles and between the coatings is the key difficulty to improve the mechanical properties of the plasma sprayed coating and further improve the comprehensive use efficiency. If the plasma spraying process can be combined with other technical means to reduce / eliminate defects and improve the interface bonding strength between the coating and the substrate / powder particles, the impact resistance / alternating stress resistance of the coating can be greatly improved, so that the wear-resistant effect of the coating can be fully played, and the application field of plasma spraying can be further widened. However, the existing single technical process cannot achieve the above purpose, especially when the coating contains diamond abrasive particles with strong surface inertness and lack of wetting ability with the substrate metal, since the SP 3The interface bonding force between the coating powder particles is weaker, and the mechanical properties of the coating are lower, which greatly affects the play of the diamond wear resistance. Therefore, on the basis of the plasma spraying process, combined with other process methods, a new combined technology process is developed to improve the density of the coating, the interface metallurgical bonding ability between the powder particles and the bonding strength between the coating and the substrate, and further improve the comprehensive mechanical properties of the coating. Ni60 is a commonly used self-fluxing thermal spraying material, and the plasma sprayed coating also has the problems of poor mechanical properties of the coating, hardness and wear resistance which are not as good as tungsten carbide. In the document "Microstructure and wear resistance of plasma sprayed-re-melted NiCrBSi coating", (Welding Journal, 2016, 37(06): 89-94+113+133.), the Ni60 coating is prepared by using the plasma spraying technology, and then the sprayed coating is subjected to plasma in-situ remelting treatment, so that the mechanical properties of the coating are greatly improved. However, a certain thermal stress is generated in the plasma in-situ remelting process, which causes cracks in the remelted coating. As can be seen, it is very important to select a suitable remelting technology for the mechanical properties of the coating. In addition, the hardness and wear resistance of the Ni60 alloy coating are still insufficient, and therefore, adding hard phases in the Ni60 powder becomes an effective means to improve the wear resistance of the coating. Diamond is the hardest material in nature, and has very strong wear resistance, but it is difficult to form effective wetting and bonding with other materials due to its strong surface chemical inertness. Therefore, it has not been applied in the field of wear-resistant coating. In order to solve the above problems, the present application uses Ni60 alloy powder as the spraying mother powder, uses D Cr as the hard additive phase, combines the plasma spraying process with the high-frequency induction technology, and performs high-frequency induction remelting treatment on the plasma sprayed coating to reduce / eliminate the coating structure porosity, realize the metallurgical reconstruction and bonding between the coating structure and the substrate, the diamond coating and the coating substrate, and the multi-layer coating, and greatly improve the comprehensive mechanical properties and wear resistance of the coating, thereby providing a feasible technical method for the engineering application of diamond in the field of wear-resistant coating. SUMMARY

[0003] In order to overcome the above technical deficiencies and improve the density, mechanical properties and wear resistance of the plasma sprayed coating, the present application provides a preparation method of a plasma sprayed / re-melted diamond-Ni-based wear-resistant coating. D Cr The coating powder is prepared by mixing the diamond powder and the Ni60 alloy powder according to the mass ratio of 10%-50%, the hard coating with a thickness of 200-300 microns is prepared on the surface of the metal part by using the plasma spraying technology, and the sprayed coating is subjected to remelting treatment by using the high-frequency induction technology, so as to prepare the densified wear-resistant coating with diamond as the reinforcing phase.

[0004] The specific technical solutions of the present application are as follows:

[0005] A method for preparing a plasma sprayed / remelted diamond-Ni-based wear-resistant coating, comprising the following steps:

[0006] 1) Selection of metal alloy powder: commercially available gas atomized Ni60 alloy powder with a particle size of 140-325 mesh is used, with a composition by weight of: Cr 17%, Si 5%, Fe 3%-5%, B 3.5%, C 0.8%-0.9%, and the balance being Ni;

[0007] 2) Preparation of D Cr : Diamond micropowder with a particle size of 10-100 μm is used, and a physical / chemical combined plating method is used to plate the diamond surface with metal Cr, with a plating weight gain of 30%-100% of the weight of the diamond micropowder, and the plating layer has a dual "core-shell" structure of "chromium carbide + elemental chromium";

[0008] 3) Blending: D Cr is 10%-50%, and the balance is gas atomized Ni60 alloy powder, and the mixture is mixed in a three-dimensional mixer for 30 min to obtain a composite functional spraying powder; the prepared mixed functional spraying powder is placed in a vacuum oven and dried at 60°C under a vacuum degree of 10 -1 Pa for 2 h, and after natural cooling, it is vacuum packaged for use;

[0009] 4) Plasma spraying to prepare a wear-resistant coating: 16-mesh white corundum is used to perform sandblasting rust removal treatment on the surface of the substrate under a working gas pressure of 0.6 MPa; before spraying, the substrate is preheated using a plasma torch to reduce the thermal stress between the coating and the substrate during spraying, and the preheating temperature is 150°C; after the pre-treatment of the substrate is completed, the spraying parameters are set as follows: spraying distance 130 mm, current 300-650 A, voltage 50-65 V, argon flow rate 60 L / min, hydrogen flow rate 0.5 L / min, and 4-10 layers of overlapping spraying;

[0010] 5) High-frequency induction remelting treatment: a high-frequency induction coil is placed below the coating to ensure good coupling between the coil and the coating; the remelting parameters are set as follows: power 1000-2000 W, distance between the induction coil and the surface of the workpiece 1-3 cm, remelting time 20-30 s, high-purity nitrogen with a purity of greater than 99.999% is used as the protective gas, and the nitrogen flow rate is 0.2 L / min; the remelted coating is naturally cooled to obtain a high-density diamond-Ni-based wear-resistant coating.

[0011] Preferably, the particle size of the diamond micropowder in step 1) is 10-15 μm.

[0012] Preferably, the plating Cr weight gain in step 2) is 100%.

[0013] Preferably, in step 3), the weight ratio of the Ni60 alloy powder to DCr The weight ratio of the mixture is 8:2.

[0014] Preferably, in step 4), the current for plasma spraying is 500A, the voltage is 60V, and 5 layers are sprayed in succession.

[0015] Preferably, in step 5), the power of the high-frequency induction remelting is 1100W, the distance between the induction coil and the workpiece surface is 1cm, and the remelting time is 20s.

[0016] Beneficial effects:

[0017] 1. This invention uses D Cr As a combination of a hard phase and atomized Ni60 alloy powder, it serves as a functionalized material for plasma spraying, preparing diamond-Ni-based wear-resistant coatings. This process improves the coating's hardness and wear resistance while promoting the formation of diamond-Ni alloys. Cr The secondary metallurgical remelting of the interface between the coating and the base metal, and the remelting and normalization of the interlayer interface during multi-layer spraying, significantly reduce the porosity of the coating substrate. This significantly improves the density, mechanical properties and wear resistance of the coating, and solves the problems of high porosity, weak metallurgical bonding between powder particles, weak interlayer bonding force during multi-layer spraying, and poor overall mechanical properties of conventional plasma spraying coatings.

[0018] 2. Core-shell structure D Cr The inner shell carbide layer exhibits good high-temperature stability, effectively protecting the diamond from oxidation and ablation in the high-temperature fields of plasma and high-frequency induction remelting, maintaining the integrity of the diamond structure and allowing it to perform its intended function. The outer shell metallic Cr can form a solid solution alloy with the coating substrate, enhancing the interfacial bonding between the diamond and the coating metal material. Furthermore, the presence of a Cr coating on the diamond surface can also improve the stability of the plasma spraying process, such as effectively reducing diamond spatter and particle rebound during spraying, and improving the deposition efficiency and density of the coating.

[0019] 3. This invention combines plasma spraying and high-frequency induction remelting processes to prepare wear-resistant coatings, effectively improving coating density, optimizing microstructure, and enhancing the bonding strength between the coating and the substrate. First, conventional plasma spraying primarily achieves mechanical bonding between the coating and the substrate. During high-frequency induction remelting, the coating melts and solidifies again, and a liquid-solid reaction occurs at the interface between the molten coating and the substrate, achieving metallurgical bonding between the interface materials. This significantly improves the interfacial bonding strength between the coating and the substrate, effectively eliminating the risk of coating detachment under stress. Second, the remelting process helps refine the coating's grain structure, eliminate microscopic defects, and form a more uniform microstructure, thereby improving the coating's hardness and wear resistance. Finally, the combination of the two processes enhances the controllability of coating preparation. Both plasma spraying and high-frequency induction remelting parameters can be adjusted independently, allowing for precise control of the coating's thickness, hardness, composition, and microstructure to adapt to more application scenarios and expand the application areas of plasma coatings. Attached Figure Description

[0020] Figure 1 D prepared in Example 1 Cr XRD pattern.

[0021] Figure 2 D prepared in Example 1 Cr SEM topography image.

[0022] Figure 3 XRD pattern of the plasma-sprayed coating of Example 1.

[0023] Figure 4 SEM image of the cross-section of the plasma-sprayed coating in Example 1.

[0024] Figure 5 XRD pattern of the coating after high-frequency induction remelting in Example 1.

[0025] Figure 6 SEM image of the cross-section of the coating after high-frequency induction remelting in Example 1. Detailed implementation method:

[0026] Example 1

[0027] 1) Preparation of D Cr Cr was deposited onto a 10-15 μm diamond surface using a combination of physical and chemical plating methods. The weight gain of the Cr plating was 100% of the weight of the diamond powder. After plating, the surface was rinsed with deionized water until the solution was neutral. The diamond powder was then rinsed... Cr Soak the diamond in alcohol for 15 minutes at a time, repeat 3 times, then place it in a vacuum drying oven to dry at room temperature for later use.

[0028] Figure 1D Cr The XRD pattern shows that Cr7C3 and Cr3C2 are formed on the diamond surface, and elemental metal Cr is also present.

[0029] Figure 2 D Cr The SEM morphology image shows a dense and uniformly distributed Cr coating layer on the surface of the diamond particles. The "steps" and edges of the diamond raw material are covered, and the coated diamonds are rounded.

[0030] 2) Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond micron powder is 8:2. Weigh 800g of Ni60 alloy powder with a particle size of 140-325 mesh for gas atomization, and weigh 200g of diamond micron powder with a particle size of 10-15μm. Cr Place the two materials into a three-dimensional mixer and mix for 30 minutes. After mixing, remove the materials and vacuum seal them for storage.

[0031] 3) Plasma spraying for preparing wear-resistant coating: The substrate material selected for this invention is an A3 steel plate with dimensions of 200mm (length) × 40mm (width) × 3mm (thickness). The substrate needs to be pretreated before spraying. The mixed powder is placed in a PRAXAIR 3710 plasma spraying equipment. The spraying parameters are: spraying distance 130mm, current 500A, voltage 60V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers are stacked.

[0032] 4) High-frequency induction remelting treatment: Place the sprayed sample in a high-frequency induction device. The remelting parameters are: power 1100W, distance between the induction coil and the workpiece surface 1cm, remelting time 20s, working gas N2, N2 flow rate 0.2L / min.

[0033] In this example, the microhardness of the plasma-sprayed coating reached 916 HV, and the microhardness of the remelted coating reached 1099 HV; the hardness after remelting increased by approximately 20% compared to before remelting. The porosity of the plasma-sprayed coating before remelting was 4.49%, and the porosity of the remelted coating was 1.61%; the porosity after remelting decreased by approximately 64% compared to before remelting.

[0034] Figure 3 The XRD pattern of the plasma-sprayed coating shows that the diamond in the coating remains intact, which confirms that the Cr layer on the diamond surface can effectively prevent the diamond from oxidizing or graphitizing under the high temperature of the plasma arc, thus maintaining the integrity of the diamond structure. At the same time, phases such as Ni4B3, NiSi, SiC and Cr7C3 are also generated in the coating.

[0035] Figure 4The cross-sectional SEM image of the plasma-sprayed coating shows that the coating and the substrate have good adhesion and the plasma-sprayed coating structure is obvious.

[0036] Figure 5 The image shows the XRD pattern of the coating after high-frequency induction remelting. It can be seen that the phase structure of the coating changes after high-frequency induction remelting. Some Ni4B3 phases decrease or decompose, while the Ni-Fe solid solution alloy phase increases, which is beneficial to improving the mechanical properties of the remelted coating.

[0037] Figure 6 The image shows the cross-sectional SEM morphology of the coating after high-frequency induction remelting. It can be seen that the coating after high-frequency induction remelting has been reconstructed into an integral metallurgically bonded welded structure. The original four-layer strip interlayer structure has been remelted and combined into one, and defects such as pores and cracks between the coating and the base material have been basically eliminated. Metallurgical bonding has also been achieved between the two interfaces.

[0038] Example 2

[0039] Plasma spraying to prepare wear-resistant coating: The mixed powder in Example 1 was placed into a PRAXAIR 3710 plasma spraying equipment, and the spraying process parameters were changed: spraying distance 130mm, current 400A, voltage 50V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers were stacked.

[0040] High-frequency induction remelting treatment: The sprayed sample is placed in a high-frequency induction device. The remelting parameters are: power 1100W, distance between the induction coil and the workpiece surface 1cm, remelting time 20s, working gas N2, N2 flow rate 0.2L / min.

[0041] In this example, the microhardness of the plasma-sprayed coating reached 1012 HV, and after remelting, the microhardness increased to 1164 HV; the hardness after remelting increased by approximately 15% compared to before remelting. The porosity of the plasma-sprayed coating before remelting was 3.92%, and the porosity after remelting was 1.44%; the porosity after remelting decreased by approximately 63% compared to before remelting.

[0042] Example 3

[0043] Plasma spraying to prepare wear-resistant coating: The mixed powder in Example 1 was placed into a PRAXAIR 3710 plasma spraying equipment, and the spraying process parameters were changed: spraying distance 130mm, current 300A, voltage 65V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers were stacked.

[0044] High-frequency induction remelting treatment: The sprayed sample is placed in a high-frequency induction device. The remelting parameters are: power 1100W, distance between the induction coil and the workpiece surface 1cm, remelting time 20s, working gas N2, N2 flow rate 0.2L / min.

[0045] In this example, the microhardness of the plasma-sprayed coating was 834 HV, and the microhardness of the remelted coating was 976 HV; the hardness after remelting was approximately 17% higher than before remelting. The porosity of the plasma-sprayed coating before remelting was 4.11%, and the porosity after remelting was 1.82%; the porosity after remelting was approximately 56% lower than before remelting.

[0046] Example 4

[0047] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond micron powder is 9:1. Weigh 900g of Ni60 alloy powder with a particle size of 140-325 mesh for gas atomization, and weigh 100g of diamond micron powder with a particle size of 10-15μm. Cr Place both into a three-dimensional mixer and mix for 30 minutes. After mixing, remove and set aside.

[0048] Plasma spraying to prepare wear-resistant coating: The mixed powder is put into a PRAXAIR 3710 plasma spraying equipment. The spraying parameters are: spraying distance 130mm, current 300A, voltage 56V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers are stacked.

[0049] High-frequency induction remelting treatment: The sprayed sample is placed in a high-frequency induction device. The remelting parameters are: power 900W, distance between the induction coil and the workpiece surface 1cm, remelting time 20s, working gas N2, N2 flow rate 0.2L / min.

[0050] In this example, the microhardness of the plasma-sprayed coating was 786 HV, and the microhardness of the remelted coating was 903 HV; the hardness after remelting increased by approximately 15% compared to before remelting. The porosity of the plasma-sprayed coating before remelting was 3.76%, and the porosity of the remelted coating was 1.28%; the porosity after remelting decreased by approximately 66% compared to before remelting.

[0051] Example 5

[0052] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond micron powder is 7:3. Weigh 700g of Ni60 alloy powder with a particle size of 140-325 mesh for gas atomization, and weigh 300g of diamond micron powder with a particle size of 10-15μm. Cr Place both into a three-dimensional mixer and mix for 30 minutes. After mixing, remove and set aside.

[0053] Plasma spraying for the preparation of wear-resistant coating: The mixed powder is placed in a PRAXAIR 3710 plasma spraying equipment. The spraying parameters are: spraying distance 130mm, current 400A, voltage 58V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers are stacked.

[0054] High-frequency induction remelting treatment: The sprayed sample is placed in a high-frequency induction device. The remelting parameters are: power 1300W, distance between the induction coil and the workpiece surface 1cm, remelting time 22s, working gas N2, N2 flow rate 0.2L / min.

[0055] In this example, the microhardness of the plasma-sprayed coating reached 1013 HV, and the microhardness of the remelted coating reached 1197 HV; the hardness after remelting increased by approximately 18% compared to before remelting. The porosity of the plasma-sprayed coating was 3.6%, and the porosity of the remelted coating was 1.13%; the porosity after remelting decreased by approximately 69% compared to before remelting.

[0056] Example 6

[0057] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond micron powder is 1:1. Weigh 500g of Ni60 alloy powder with a particle size of 140-325 mesh for gas atomization, and weigh 500g of D micron powder with a particle size of 10-15μm. Cr Place both into a three-dimensional mixer and mix for 30 minutes. After mixing, remove and set aside.

[0058] Plasma spraying for the preparation of wear-resistant coating: The mixed powder is placed in a PRAXAIR 3710 plasma spraying equipment. The spraying parameters are: spraying distance 130mm, current 500A, voltage 60V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4 layers are stacked.

[0059] High-frequency induction remelting treatment: The sprayed sample is placed in a high-frequency induction device. The remelting parameters are: power 1500W, distance between the induction coil and the workpiece surface 1cm, remelting time 20s, working gas N2, N2 flow rate 0.2L / min.

[0060] In this example, the microhardness of the plasma-sprayed coating reached 957 HV, and after remelting, the microhardness increased to 1178 HV; the hardness after remelting increased by approximately 23% compared to before remelting. The porosity of the plasma-sprayed coating was 4.58%, and the porosity of the remelted coating was 1.63%; the porosity after remelting decreased by approximately 64% compared to before remelting.

Claims

1. A method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating, comprising the following steps: 1) Selection of metal alloy powder: Commercially available gas-atomized Ni60 alloy powder with a particle size of 140-325 mesh was used. The weight ratio of the components was: Cr 17%, Si 5%, Fe 3%-5%, B 3.5%, C 0.8%-0.9%, and the balance was Ni. 2) Preparation of D Cr Diamond micro powder with a particle size of 10-100μm is used to coat the diamond surface with metallic Cr using a combination of physical and chemical plating methods. The weight gain of the Cr coating is 30%-100% of the weight of the diamond micro powder. The coating is characterized by a dual "core-shell" structure of "chromium carbide + elemental chromium". 3) Ingredients: As per D Cr The composite functional coating powder is obtained by mixing 10%-50% (by weight) of gas-atomized Ni60 alloy powder in a three-dimensional mixer for 30 minutes; the prepared composite functional coating powder is then placed in a vacuum oven and dried at 60°C and a vacuum degree of 10. -1 Dry under Pa conditions for 2 hours, then vacuum-seal after natural cooling for later use. 4) Plasma spraying for wear-resistant coating: 16-mesh white corundum is used to sandblast and remove rust from the substrate surface under a working gas pressure of 0.6MPa. Before spraying, the substrate is preheated with a plasma spray gun to reduce the thermal stress between the coating and the substrate during spraying. The preheating temperature is 150℃. After the substrate is pretreated, the spraying parameters are set as follows: spraying distance 130mm, current 300-650A, voltage 50-65V, argon flow rate 60L / min, hydrogen flow rate 0.5L / min, and 4-10 layers are stacked. 5) High-frequency induction remelting treatment: Place the high-frequency induction coil under the coating to ensure good coupling between the coil and the coating; set the remelting parameters as follows: power 1000-2000W, distance between the induction coil and the workpiece surface 1-3cm, remelting time 20-30s, use high-purity nitrogen with a purity greater than 99.999% as the protective gas, and nitrogen flow rate 0.2L / min; after remelting, the coating is naturally cooled to obtain a high-density diamond-Ni-based wear-resistant coating.

2. The method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating according to claim 1, characterized in that, The diamond powder in step 1) has a particle size of 10-15 μm.

3. The method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating according to claim 1, characterized in that, The Cr plating weight gain in step 2) is 100%.

4. The method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating according to claim 1, characterized in that, Step 3) Ni60 alloy powder and D Cr The weight ratio of the mixture is 8:

2.

5. The method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating according to claim 1, characterized in that, Step 4) The current for plasma spraying is 500A, the voltage is 60V, and 5 layers are sprayed in succession.

6. The method for preparing a plasma-sprayed / remelted diamond-Ni-based wear-resistant coating according to claim 1, characterized in that, In step 5), the power of high-frequency induction remelting is 1100W, the distance between the induction coil and the workpiece surface is 1cm, and the remelting time is 20s.

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