Bonding and wear behaviors of supersonic plasma sprayed Fe-based coatings on Al-Si alloy substrate

Abstract

The quality of plasma sprayed coatings is governed by both bond and wear properties during the service period, associated with a number of factors including substrate surface conditions, materials composition, phase transformation, and etc. In the present study, three different Fe-based powder materials including gray cast iron, high chrome steel and high chrome and nickle contained self-fluxing powders were plasma sprayed onto the Al-Si alloy substrate. The microstructure, hardness, phase composition, bonding strength and wear properties of the deposited coatings were investigated. The XRD results revealed that severe oxidation of gray cast iron coatings occurred during the deposition, while no obvious oxidation and phase transformation were detected for chrome steel coatings after spraying. However, the transition of γ-(Fe, Ni) phase into α-(Fe,Cr) phase was confirmed in the self-fluxing coatings. In addition, the Cr and Ni alloying elements enhanced the diffusion between Fe and Al across the coating-substrate interface. Three types of Fe-based coatings showed improved wear resistance in comparison to Al-Si alloy substrate, in terms of coefficient of friction, mass and volume loss. The chrome steel coatings have better integrated performance of bond strength and wear properties. Distinct wear mechanisms were revealed for three types of coatings, i.e. a mixture of adhesive and abrasive wear for gray cast iron coatings, an oxidation dominant wear for chrome steel coatings, and a mixture of oxidation and fatigue wear for self-fluxing coatings.