冷喷涂硬质合金耐磨涂层研究进展

Research Progress of Cold Sprayed Cermet Wear-resistant Coating

硬质合金涂层具有高耐磨性与高耐腐蚀性等优势,因此广泛应用于冶金等领域的耐磨、耐蚀防护中。采用传统热喷涂技术制备硬质合金涂层,其高温会导致涂层材料产生相变、氧化、脱碳等问题,从而损害涂层的服役性能。冷喷涂技术作为一种新兴的涂层制备技术,具有低温的特点,可避免传统热喷涂方法所带来的涂层质量问题,成为硬质合金涂层制备的潜在技术。在简述冷喷涂技术原理及其沉积机理的基础上,综述了冷喷涂制备硬质合金耐磨涂层(如WC-Co、WC-Ni、Cr_(3)C_(2)-NiCr等),以及影响涂层硬度、耐磨性等力学性能的主要因素,包括硬质相、黏结相的种类、含量和尺寸等。综合比较了冷喷涂与超音速火焰喷涂制备的硬质合金涂层的耐磨性能,分析了后处理(喷后热处理、搅拌摩擦处理)对冷喷涂硬质合金涂层耐磨性的影响。最后,提出了冷喷涂技术在硬质合金耐磨涂层制备方面的局限性,并对未来发展进行了展望。

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 andηphases,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,Cr_(3)C_(2)-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.