PROPERTIES OF ALLOY-STEEL COATINGS OXIDIZED DURING PLASMA SPRAYING

Plasma spraying of metals in air is usually accompanied by oxidation r eactions resulting in the presence of oxides in plasma deposited coati ngs. Oxides in plasma sprayed high-alloy steel coatings can strongly a ffect their protective and mechanical properties. Two high-alloy steel s were plasma sprayed onto plain steel substrates using a water-stabil ized plasma gun. Both coating types, composed as usual of metallic lam ellae (splats), contained considerable amounts of oxides present mainl y as thin oxide films enveloping the splats. The compressive behaviour of cubic samples cut out of the coatings was studied. The results ind icate an appreciable anisotropy of the response to compressive loading . If the pressure is parallel to the coating surface, strong cracking occurs. For loading perpendicular to the surface, cracking is less pro nounced and high values of plastic deformation are observed. Though th e coating structure and the presence of oxides preclude a satisfactory tensile strength, the coating can withstand high purely compressive l oading. In this respect, plasma sprayed steels are comparable to those produced by conventional metallurgy. (C) 1997 Elsevier Science S.A.