Preparation method of plasma spraying / remelting diamond-Ni-based wear-resistant coating

Abstract

The invention 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. The preparation method comprises the following five steps: selecting metal alloy powder, preparing a Cr-plated diamond, proportioning, preparing the wear-resistant coating by plasma spraying, and performing high-frequency induction remelting treatment. According to the special technical process for preparing the diamond wear-resistant coating, which is developed by combining the material characteristics and the process method, a new engineering technical route is provided for improving the wear resistance of the coating by using diamond as a super wear-resistant hard phase.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of wear-resistant coatings, and specifically relates to a method of using atomized Ni60 alloy powder as a basic raw material to plate Cr diamond (D Cr ) is used as a hard phase to prepare a coating composite functional powder, and a method for preparing a wear-resistant coating by coating the composite functional powder on the surface of a metal part using a combination of plasma spraying / high-frequency induction remelting processes. Background Art

[0002] With the rapid development of large-scale / automated / intelligent equipment, the requirements for the wear resistance of key equipment components are getting higher and higher, especially for engineering machinery components such as mining machinery, coal machinery, and petroleum equipment that operate in harsh environments. They must withstand multiple tests such as extreme loads, severe impacts, and strong wear. In order to improve the surface wear resistance of workpieces, surface hardening treatment technologies such as laser cladding and plasma spraying are often used in engineering applications to apply a certain thickness of hard wear-resistant layer on the surface of metal parts. Plasma spraying uses a plasma arc as a heat source to locally melt the surface of the sprayed hard metal or ceramic powder, and uses a high-speed ion flow to spray powder particles onto the surface of the workpiece to form a wear-resistant coating. However, since the interfacial bonding between the deposited powder particles of the plasma spray coating is formed by condensation connection of the local melting area on the surface, there are some weaknesses: 1) The interfacial bonding strength between the coating powder and the workpiece substrate is low; 2) The interfacial bonding strength between the powder particles is low, especially the bonding strength between heterogeneous materials such as metal and ceramic is even lower; 3) The coating density is insufficient, the strength is low, and there are many microscopic defects such as pores and cracks; 4) The interlayer bonding strength is low during multi-layer spraying; 5) The internal residual stress of the coating is too large, which can easily cause the coating to peel off and peel under the action of dynamic load. The above problems weaken the bonding strength of the coating and greatly affect the application efficiency of plasma spraying. Therefore, how to improve the bonding strength between the plasma spray 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 spray coating and thus improve its 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 coating's impact resistance / alternating stress resistance can be greatly improved, thereby giving full play to the coating's wear resistance and further broadening the application field of plasma spraying. 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 wettability with the substrate metal. Due to the SP 3The bond energy is extremely high, and it is difficult to form effective wetting and metallurgical bonding with other materials. The interface bonding force between the coating powder particles is weaker, and the mechanical properties of the coating are lower, which greatly affects the wear resistance of diamond. Therefore, it is necessary to develop a new combination technology based on the plasma spraying process and combine other process methods 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, thereby improving the comprehensive mechanical properties of the coating. Ni60 is a commonly used self-melting thermal spray material. Its plasma sprayed coating also has the disadvantages of poor mechanical properties, hardness and wear resistance inferior to tungsten carbide. The literature "Microstructure and Wear Resistance of Plasma Sprayed-Remelted NiCrBSi Coating" (Journal of Welding, 2016, 37(06): 89-94+113+133.) uses plasma spraying technology to prepare Ni60 coating, and then plasma in-situ remelting treatment is performed on the sprayed coating, and the mechanical properties of the coating are greatly improved. However, certain thermal stress is generated during the plasma in-situ remelting process, resulting in cracks in the remelted coating. It can be seen that choosing a suitable remelting technology is crucial for the mechanical properties of the coating. In addition, the hardness and wear resistance of the Ni60 alloy coating are still lacking. Therefore, adding a hard phase to the Ni60 powder becomes an effective means to improve the wear resistance of the coating. Diamond, as the hardest substance in nature, has extremely strong wear resistance, but due to its strong chemical inertness on the surface and difficulty in forming effective wetting and bonding with other materials, it has not yet been applied in the field of wear-resistant coatings. In order to solve the above problems, the present invention uses Ni60 alloy powder as the spraying mother powder and D Cr In order to add hard phases, the plasma spraying process is combined with high-frequency induction technology, and the plasma sprayed coating is subjected to high-frequency induction remelting treatment to reduce / eliminate the pores in the coating structure, and to achieve metallurgical reconstruction of the coating structure and the parent substrate, the diamond coating and the coating substrate, and the multi-layered structure of the coating, thereby greatly improving the comprehensive mechanical properties and wear resistance of the coating, and providing a feasible technical method for the engineering application of diamond in the field of wear-resistant coatings. Summary of the invention

[0003] In order to overcome the above technical deficiencies and improve the density, mechanical properties and wear resistance of plasma sprayed coatings, the present invention provides a method for preparing plasma sprayed / remelted diamond-Ni based wear-resistant coatings. Cr The coating powder is prepared by mixing with Ni60 alloy powder in a mass ratio of 10%-50%, and a 200μm-300μm hard coating is sprayed on the surface of the metal parts using plasma spraying technology. The sprayed coating is then remelted using high-frequency induction technology to prepare a densified wear-resistant coating with diamond as the reinforcement phase.

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

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

[0006] 1) Selection of metal alloy powder: Use commercially available gas-atomized Ni60 alloy powder with a particle size of 140-325 mesh, with a component weight ratio of: Cr17%, Si5%, Fe3%-5%, B3.5%, C0.8%-0.9%, and the balance is Ni;

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

[0008] 3) Ingredients: Press D Cr The weight ratio of the atomized Ni60 alloy powder is 10%-50% and the balance is atomized Ni60 alloy powder, and the mixture is mixed in a three-dimensional mixer for 30 minutes to obtain a composite functional spray powder; the prepared mixed functional spray powder is placed in a vacuum oven at 60°C and a vacuum degree of 10 -1 Dry under Pa conditions for 2 h, cool naturally and vacuum package for later use;

[0009] 4) Preparation of wear-resistant coating by plasma spraying: using 16-mesh white corundum, the substrate surface was sandblasted and rust-removed at a working pressure of 0.6 MPa; the substrate was preheated with a plasma spray gun before spraying to reduce the thermal stress between the coating and the substrate during spraying. The preheating temperature was 150°C. After the pretreatment of the substrate was completed, the spraying parameters were 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: 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; 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 powder in step 1) is 10-15 μm.

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

[0013] As a preferred method, in step 3), the Ni60 alloy powder and DCr The mixing weight ratio is 8:2.

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

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

[0016] Beneficial effects:

[0017] 1. The present invention uses D Cr As a hard phase combined with atomized Ni60 alloy powder, as a functional material used in plasma spraying, diamond-Ni based wear-resistant coating was prepared, which not only improved the hardness and wear resistance of the coating, but also promoted the D Cr The secondary metallurgical remelting of the interface with the base metal is combined, and the interlayer interface remelting during multi-layer spraying is normalized, which greatly reduces the porosity of the coating substrate, thereby significantly improving the density, mechanical properties and wear resistance of the coating, and solves the problems of high porosity, weak metallurgical bonding ability between powder particles, weak interlayer interface bonding during multi-layer spraying, and poor overall mechanical properties of conventional plasma sprayed coatings.

[0018] 2. "Core-shell" structure D Cr The inner shell carbide has good high-temperature stability, which can effectively protect the diamond from oxidation and ablation in the high-temperature field of plasma and high-frequency induction remelting, maintain the integrity of the diamond structure, and enable it to play its due role. The metal Cr in the outer shell can form a solid solution alloy with the coating matrix, enhancing the interface bonding force between the diamond and the coating metal material. In addition, the presence of the Cr-plated layer on the diamond surface can also improve the stability of the plasma spraying process, such as effectively reducing the splashing and particle rebound of diamond during the spraying process, and improving the deposition efficiency and density of the coating.

[0019] 3. The present invention combines the two processes of plasma spraying and high-frequency induction remelting to prepare a wear-resistant coating, which can effectively improve the density of the coating, optimize the microstructure and improve the bonding strength between the coating and the substrate. First, the bonding form between the conventional plasma sprayed coating and the component substrate is mainly mechanical bonding. During the high-frequency induction remelting process, the coating melts again and re-solidifies. The molten coating and the component substrate undergo a liquid-solid reaction at the interface to achieve metallurgical bonding between the interface materials, significantly improving the interface bonding strength between the coating and the substrate, thereby effectively eliminating the risk of the coating falling off due to stress. Secondly, the remelting process helps to refine the grain structure of the coating, eliminate microscopic defects, and form a more uniform microstructure, thereby improving the hardness and wear resistance of the coating. Finally, the combination of the two processes helps to improve the controllability of coating preparation. Both the plasma spraying parameters and the high-frequency induction remelting parameters can be adjusted independently, allowing for fine control of the thickness, hardness, composition and microstructure of the coating to adapt to more application scenarios, expanding the application field of plasma coatings. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 D prepared in Example 1 Cr SEM morphology of the samples.

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

[0023] Figure 4 Cross-sectional SEM morphology of the plasma sprayed coating of Example 1.

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

[0025] Figure 6 Cross-sectional SEM morphology of the coating after high-frequency induction remelting in Example 1. DETAILED DESCRIPTION

[0026] Example 1

[0027] 1) Preparation of D Cr : Use physical / chemical combined plating method to plate Cr on the surface of 10-15μm diamond, and the weight of Cr plating is 100% of the weight of diamond powder. After plating, wash with deionized water until the solution is neutral. Cr Put it in alcohol and ultrasonicate it for 15 minutes each time, for 3 times. Then put the diamond into a vacuum drying oven and dry it at room temperature for later use.

[0028] Figure 1 DCr From the XRD diagram, it can be seen that Cr7C3 and Cr3C2 are generated on the diamond surface, and there is also elemental metal Cr.

[0029] Figure 2 D Cr From the SEM morphology, a dense and evenly distributed Cr-plated layer can be observed on the surface of the diamond particles. The "steps" and edges of the diamond raw material are covered, and the coated diamond is rounded.

[0030] 2) Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond powder is 8:2. Weigh 800g of atomized Ni60 alloy powder with a particle size of 140-325 mesh, weigh 200g of D Cr , put the two into a three-dimensional mixer and mix for 30 minutes. After mixing, take them out and store them in a vacuum package.

[0031] 3) Preparation of wear-resistant coating by plasma spraying: The substrate material selected in the present invention is an A3 steel plate of 200 mm (length) × 40 mm (width) × 3 mm (thickness), and the substrate needs to be pre-treated before spraying. The mixed powder is placed in a PRAXAIR3710 plasma spraying equipment, and the spraying parameters are: spraying distance 130 mm, current 500 A, voltage 60 V, argon flow 60 L / min, hydrogen flow 0.5 L / min, and 4 layers of overlapping spraying.

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

[0033] In this example, the microhardness of the plasma sprayed coating reaches 916HV, and the microhardness of the coating after remelting reaches 1099HV; the hardness after remelting increases by about 20% compared with that before remelting. The porosity of the plasma sprayed coating before remelting is 4.49%, and the porosity of the coating after remelting is 1.61%; the porosity after remelting is reduced by about 64% compared with that before remelting.

[0034] Figure 3 This is the XRD diagram of the plasma sprayed coating. It can be found that the diamond in the plasma sprayed coating is intact, which also confirms that the Cr layer on the diamond surface can effectively prevent the diamond from being oxidized or graphitized under the high temperature of the plasma arc and maintain the integrity of the diamond structure; at the same time, Ni4B3, NiSi, SiC and Cr7C3 phases are also generated in the coating.

[0035] Figure 4This is a cross-sectional SEM morphology of the plasma sprayed coating. It can be found that the coating is well bonded to the substrate and the plasma sprayed coating structure is obvious.

[0036] Figure 5 This is the XRD diagram of the coating after high-frequency induction remelting. It can be seen that after the high-frequency induction remelting treatment, the phase structure of the coating has changed. Part of the Ni4B3 phase has been reduced or decomposed, and the Ni-Fe solid solution alloy phase has increased, which is beneficial to improving the mechanical properties of the remelted coating.

[0037] Figure 6 This is 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 overall metallurgically bonded welding structure. The original 4-layer banded interlayer structure has been remelted and combined to become one. The defects such as pores and cracks between the coating and the base material are basically eliminated, and metallurgical bonding is also achieved between the interface of the two.

[0038] Example 2

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

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

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

[0042] Example 3

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

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

[0045] The microhardness of the plasma sprayed coating in this example is 834HV, and the microhardness of the coating after remelting is 976HV; the hardness after remelting is about 17% higher than that before remelting. The porosity of the plasma sprayed coating before remelting is 4.11%, and the porosity of the coating after remelting is 1.82%; the porosity after remelting is about 56% lower than that before remelting.

[0046] Example 4

[0047] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond powder is 9:1. Weigh 900g of atomized Ni60 alloy powder with a particle size of 140-325 mesh, weigh 100g of D Cr , put the two into a three-dimensional mixer and mix for 30 minutes. After mixing, take them out for use.

[0048] Preparation of wear-resistant coating by plasma spraying: The mixed powder was placed in a PRAXAIR 3710 plasma spraying equipment with the following spraying parameters: spraying distance 130 mm, current 300 A, voltage 56 V, argon flow rate 60 L / min, hydrogen flow rate 0.5 L / min, and 4 layers of overlapping spraying.

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

[0050] The microhardness of the plasma sprayed coating in this example is 786HV, and the microhardness of the coating after remelting is 903HV; the hardness after remelting is about 15% higher than that before remelting. The porosity of the plasma sprayed coating before remelting is 3.76%, and the porosity of the coating after remelting is 1.28%; the porosity after remelting is about 66% lower than that before remelting.

[0051] Example 5

[0052] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond powder is 7:3. Weigh 700g of atomized Ni60 alloy powder with a particle size of 140-325 mesh, weigh 300g of D Cr , put the two into a three-dimensional mixer and mix for 30 minutes. After mixing, take them out for use.

[0053] Preparation of wear-resistant coating by plasma spraying: The mixed powder was placed in a PRAXAIR 3710 plasma spraying equipment with the following spraying parameters: spraying distance 130 mm, current 400 A, voltage 58 V, argon flow rate 60 L / min, hydrogen flow rate 0.5 L / min, and 4 layers of overlapping spraying.

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

[0055] In this example, the microhardness of the plasma sprayed coating reached 1013HV, and the microhardness of the coating after remelting reached 1197HV; the hardness after remelting increased by about 18% compared with that before remelting. The porosity of the plasma sprayed coating was 3.6%, and the porosity of the coating after remelting was 1.13%; the porosity after remelting was reduced by about 69% compared with that before remelting.

[0056] Example 6

[0057] Coating powder preparation: The weight ratio of Ni60 alloy powder to diamond powder is 1:1. Weigh 500g of atomized Ni60 alloy powder with a particle size of 140-325 mesh, weigh 500g of D Cr , put the two into a three-dimensional mixer and mix for 30 minutes. After mixing, take them out for use.

[0058] Preparation of wear-resistant coating by plasma spraying: The mixed powder was placed in a PRAXAIR 3710 plasma spraying equipment with the following spraying parameters: spraying distance 130 mm, current 500 A, voltage 60 V, argon flow rate 60 L / min, hydrogen flow rate 0.5 L / min, and 4 layers of overlapping spraying.

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

[0060] In this example, the microhardness of the plasma sprayed coating reached 957HV, and the microhardness of the coating after remelting increased to 1178HV; the hardness after remelting increased by about 23% compared with that before remelting. The porosity of the plasma sprayed coating was 4.58%, and the porosity of the coating after remelting was 1.63%; the porosity after remelting was reduced by about 64% compared with that 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: Use commercially available gas-atomized Ni60 alloy powder with a particle size of 140-325 mesh, with a component weight ratio of: Cr17%, Si5%, Fe3%-5%, B3.5%, C0.8%-0.9%, and the balance is Ni; 2) Preparation of D Cr :Using diamond micropowder with a particle size of 10-100μm, the metal Cr is plated on the diamond surface using a physical / chemical combined plating method. The weight gain of the Cr plating layer is 30%-100% of the weight of the diamond micropowder. The coating is characterized by a double "core-shell" structure of "chromium carbide + elemental chromium"; 3) Ingredients: Press D Cr The weight ratio of the atomized Ni60 alloy powder is 10%-50% and the balance is atomized Ni60 alloy powder, and the mixture is mixed in a three-dimensional mixer for 30 minutes to obtain a composite functional spray powder; the prepared mixed functional spray powder is placed in a vacuum oven at 60°C and a vacuum degree of 10 -1 Dry under Pa conditions for 2 h, cool naturally and vacuum package for later use; 4) Preparation of wear-resistant coating by plasma spraying: using 16-mesh white corundum, the substrate surface was sandblasted and rust-removed at a working pressure of 0.6 MPa; the substrate was preheated with a plasma spray gun before spraying to reduce the thermal stress between the coating and the substrate during spraying. The preheating temperature was 150°C. After the pretreatment of the substrate was completed, the spraying parameters were 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; 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; the remelted 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 particle size of the diamond powder in step 1) is 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 weight gain of Cr plating 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 mixing weight ratio 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: In step 4), the current of plasma spraying is 500A, the voltage is 60V, and 5 layers are sprayed in stack.

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

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