Study On Al₂O₃ Particles Reinforced Ni-Based Alloy Composite Coating Of Microstructure And Wear Resistance

In harsh conditions（with high wear a nd corrosion resistance）, Ni60 A alloy powder is difficult to meet the use requirements.It is very signifance to enhance the wear resistance, corrosion resistance through adding a or a more enhanced particle of composite coating the research in a nickel base self fluxing alloy powder, This paper in Ni60 A alloy powder, adding different volume fraction of Al₂O₃ particles reinforced powder, th e mechanical mixing by ball mill, and using the supersonic plasma spraying technology respectively different volume fraction of the composite powder spray evenly to 45# steel substrate surface prepared Al 2O3 particles reinforced Ni60 A composite coatings.Through hardness test and wear test showed that the composite coating hardness and wear rate than Ni60 A alloy coating changed obviously, with the volume fraction of Al 2O3 increased the hardness values first increased and then decreased, and the wear decreas ed first and then increased and when Al₂O₃ volume fraction is 25%, the coating hardness and wear resistance is best. 25% Al₂O₃ the hardness value of composite coating and Ni60 A alloy coating is the biggest difference. The hardness of the 25% Al₂O₃ composite coating was 63.14 HRC, while the hardness of the Ni 60 A alloy coating was only 59.2 HRC. 25% Al₂O₃ composite coating quality wear rate `and friction coefficient were 0.153 and 0.46, respectively, and Ni60 A alloy coating were 1.025 and 0.8, according to con trast experiment, the wear resistance of the 25% Al₂O₃ composite coating than Ni60 A alloy coating improves the 6.7 times.The morphology, composition and phase structure of Al₂O₃ composite coating and Ni60 A alloy coating were analyzed by scanning electron microscopy, energy dispersive spectroscopy and X-ray detection and analysis. The results show ed that: by ball milling the mixture powder is spherical and irregular bulk composition, between two kinds of alloy powder exist obvious mechanical adhesion and so lid phase diffusion phenomenon. This enhances the heat conduction in th e process of powder spraying, was conducive to the full of powder melting, integration and wetting, improved the spray deposition rate and significantly improved the spraying effect. Mi crostructure of composite coating Al₂O₃-Ni60 A existed nickel, chromium of austenite in the matrix organization, matrix precipitation of acicular structure and plate strip electron compounds and Ni60 A coating Al₂O₃ pellet shaped reinforced particle organiza tion and evenly dispersed in the matrix. Al₂O₃-Ni60 A composite coating is tough and matrix and the hard phase wear-resisting structure matrix are good toughness of Ni and Cr base solid solution, composite coating of hard phase is mainly Al₂O₃ particles and the matrix on the precipitation of Cr2 3C6, Cr B, Ni3 B, Cr7C3, Ni5Al3,Al Ni,Al₂O₃ and hard phase. Solid compound needle like pellets of Al₂O₃ composite coating Al₂O₃ pellet shaped reinforced particles increases the matrix deformation energy, strengthen the m atrix; matrix on a uniform distribution of the tissue to improve the original precipitates electronic form of matrix separation; in the spraying process, part of Al₂O₃ decomposition, to form a new hard phase, Al₂O₃ particles but also help to solidification nucleation and grain refinement, which shows that the composite coating Al₂O₃ particles to the pellet shaped distribution in Ni60 A matrix, is the main wear particle, coupled with composite coating also has a variety of precipitation of hard phase, and to improve and strengthen the austenite matrix, the wear resistance significantly improved.Corrosion test results show that: by immersion test and electrochemical corrosion experiment, a study was conducted on the corrosion resistance of two kinds of alloy coating in 1mol/ L HCl solution and 1mol/ L H2SO4 solution, composite coating and Ni60 A alloy coating are different. In H2SO4 solution, the composite coating and Ni60 A alloy have considerable corrosion resistance, while in HCl solution, the corrosion resistan ce of the composite coating is much better than that of the Ni60 A alloy coating.Through comparative analysis of performances of Al₂O₃-Ni60 A composite coating and single alloy coating, composite coating with Al₂O₃ particles play an important role in improvi ng the wear resistance of the coatings. W hen the added reinforcing partiles was 25%, coating wear resistance best, it is the best ratio. Wear resistance of single alloy coating is increased by 85% than that of Ni60 A alloy, and the corrosion resistance of N i60 A alloy is equal to that of the alloy. Al₂O₃ material prices are cheaper, some alternative to expensive Ni60 A materials, can significantly reduce the cost of spraying, so Al₂O₃ reinforced particulate Ni60 A composite coating has a very good price, with a wide range of promotional value.