High-Temperature ZrB.sub.2-Based Coatings on Metallic Alloys Produced by High-Velocity Air-Fuel Thermal Spraying

The composition and structure of ZrB.sub.2-based coatings with MoSi.sub.2, SiC, and AlN additions on metallic alloys produced by high-velocity air-fuel thermal spraying are studied. The use of composite powders with a low content of the NiCr binder ([less than or equal to]10 wt.%) is shown to be beneficial due to intensive adhesive interaction of the components. The phase transformations induced by high-temperature thermodynamically nonequilibrium processes, including oxygen-assisted ones, occur when the coatings are being formed. The coatings with a hardness of ~15 GPa and a porosity of [less than or equal to]4% are characterized by a granular structure without cracks and have a 50-120 [mu]m thick ceramic layer and an interfacial layer of uniform width (~10 [mu]m) at the boundary between the NiCr alloy and stainless steel.