Microstructural and mechanical properties of nickel-base plasma sprayed coatings on steel and cast iron substrates

Abstract

This paper studies the phase composition, microstructure, hardness and wear resistance of nickel-base plasma sprayed coatings, on two types of substrates, steel and cast iron. The processing method of metal and compound powders for plasma spraying is detailed, together with the characteristics of the powders before and after processing. It has been found that in as-coated condition, the surface layers have phase composition of crystalline γ-Ni solid solution and amorphous phases on steel substrate. On cast iron substrate, in addition to these, Ni 3B, CrB, Cr 23C 6 have been identified. The effect of heat treatment of coatings on steel substrate at temperatures up to 1200 °C has been investigated. It has been found that the coatings have high values of hardness and wear resistance. There are changes in the phase compositions on the surface of the Ni-base coatings during wear testing upon the effect of friction heat, and the wear volume after 60 min for the coating on cast iron substrate is much lower than for those on steel substrate.