冷喷涂硬质合金耐磨涂层研究进展

Cermet coating is composed of metal bonding phase and carbide hard phase, which combines the toughness of metal and the high hardness of ceramic. It has the advantages of high wear resistance and corrosion resistance, so it is widely used in wear resistance, corrosion resistance and other protection fields in aviation, aerospace, metallurgy and so on. When using traditional thermal spraying technology to prepare cermet coatings, the high temperature will lead to phase transformation, oxidation, decarburization and other problems of the coatings. For example, WC changes into W₂C, W and η phases, and the overall coating becomes brittle, thus reducing the wear resistance of the coatings and restricting its further application. Cold spray technology, as a new coating preparation technology, avoids the coating quality degradation problems caused by traditional thermal spraying methods because of its low temperature characteristic. The resulting coating has a dense texture. The residual stress of the coating prepared by cold spraying is usually compressive stress, which not only does not damage the fatigue life of the substrate, but also improves the fatigue life, and becomes a potential technology for the preparation of cermet coatings. On the basis, the work provided a simple description of the cold spray principle, including two kinds of cold spraying system (high pressure cold spraying, low pressure cold spraying), focusing on the working principle of high pressure cold spraying technology, and the bonding mechanism of cold spraying particles, mechanical occlusion between particle and matrix, the adiabatic shear instability mechanism and the damage mechanism of oxide film on powder surface. The concept of critical velocity and generalized parameter window for cold spray deposition were introduced. The material fields involved in cold spraying technology were described briefly. Pure metal, metal alloy, metal-ceramic composite and high entropy alloy were deposited on a variety of substrates. The applications of cold spraying technology, including coating preparation, structure repair and additive manufacturing, were also described. The cold spray preparation of cermet wear-resistant coatings (such as WC-Co, WC-Ni, Cr₃C₂-NiCr, etc.), as well as the main factors affecting the hardness, wear resistance and other mechanical properties of coatings, including the type, content and size of hard phase and bond phase, etc. were discussed. Macroscopically, the differences between microstructure, hardness and wear resistance of cold sprayed cermet coatings were expounded from powder design and process parameters. Microscopically, the differences between microstructure, hardness and wear resistance of cold sprayed cermet coatings were expounded from mean free path of cermet particles, distribution uniformity and particle size (especially nano-sized particles). The microhardness and wear properties of the cermet coatings prepared by cold spraying and high velocity oxy-fuel spray were compared comprehensively. The cold spraying composite processing technology was discussed, and the effect of post-treatment (heat treatment after spraying, friction stir treatment) on the wear resistance of the cermet coating was analyzed. Finally, the research achievements of cold spraying cermet wear-resistant coatings were summarized, and the limitations of the current cold spray technology in the preparation of cermet wear-resistant coatings were presented, including powder design, process cost deficiencies, and its future prospects were presented.