Preparation And Properties Of Ni+WC Three-dimensional Mesh Texture Composite Coating Layer On Cast Steel Surface

Composites formed by adding different ceramic particles into metal-based alloy powders have good resistance to various forms of wear and corrosion,which is mainly due to the combination of hard particles and tough matrix.The nickel-based composites with WC reinforcement particles are widely used to prepare various mechanical equipment parts requiring high wear resistance and corrosion resistance,so as to improve their performance and life,such as mining equipment,abrasive tools and instruments.In this paper,nickel-based composite coatings with dispersed structure and three-dimensional mesh texture were prepared on 45 steel surface by vacuum cladding technology.The microstructure,phase composition and formation mechanism of the coating were studied.The corrosion and wear properties of the composite coatings with different compositions and structures were tested.The experimental results show that the Ni+30%WC composite coating with three-dimensional mesh texture is prepared on the surface of 45 steel by vacuum cladding technology.three-dimensional mesh texture is mainly composed ofγ-Ni,Ni₃Fe,Ni₃Si,Ni₃B,Cr₇C₃,Cr₂₃C₆,WC,W₂C,C and Ni_2.9Cr_0.7Fe_0.36.Element diffusion occurs at the interface junction,and the diffusion depth is about 30μm.A solid metallurgical bonding is formed between the substrate and the cladding layer.The three-dimensional reticular texture distributes uniformly and continuously in the cladding layer.Hard WC and its partially decomposed W₂C particles form a three-dimensional mesh texture“netting twine”,Ni₃Fe,Ni₃Si,Cr₇C₃,Cr₂₃C₆ and Ni-based solid solution form a three-dimensional mesh texture“mesh”.The addition of WC particles in the nickel-based coating effectively improves the corrosion resistance of the coating.In the dispersion structure,with the increase of WC content,the number of decomposed small W₂C particles increases,and the defects formed on the cladding layer due to non-wetting also increase.In addition,the content of C element near W₂C particles is high,which is easy to form galvanic corrosion.Therefore,in the dispersion structure,the corrosion resistance of the cladding layer gradually decreases with the increase of WC content.In the three-dimensional mesh texture,when the WC content is 20%,the three-dimensional mesh texture is incomplete,there are gaps in the protective film composed of hard phase,and the ions are easy to diffuse.When the WC content is 30%,the protective film composed of hard phase is relatively complete,which can effectively hinder the diffusion of Cl^-,so that the corrosion resistance of Ni+30%WC coating is better than that of Ni+20%WC coating.After adding WC particles in the nickel-based composite cladding layer,the wear resistance of the material is effectively improved.Compared with 45 steel,the average friction coefficient and wear rate of Ni+30%WC composite coating with three-dimensional mesh texture decreased by 13%and 61.4%,respectively.In the composite coating of Ni+20%WC,the wear rate of the three-dimensional mesh texture coating is 9.7%lower than that of the dispersion distribution structure coating.In the Ni+30%WC composite coating,the average friction coefficient and wear rate of the three-dimensional mesh texture coating were reduced by 4%and 11.8%,respectively,compared with those of the dispersion structure coating.