Rapidly Solidified Thick Deposit of Fe-B-Cr Alloy by Plasma Spraying

Abstract

Fe-B-Cr alloy powder in diameter of 32-53 μm made by argon atomization is low-pressure plasma sprayed to produce a rapidly solidified iron base composite deposit with finely dispersed boride particles. The constituents of the as-sprayed deposit formed on a water-cooled substrate are α phase and amorphous phase that are supersaturated with chromium and boron due to high cooling rate during solidification of the melt. Heat treatment of deposit at 873K leads to decomposition of the amorphous phase, resulting in the formation of Fe3B. The deposit heat treated above 1073K is composed of α phase and (Fe,Cr)2B. The as-sprayed deposit produced on a non-cooled substrate consists of α phase and (Fe,Cr)2B. The fine precipitates of about 0.1 μm in the as-sprayed deposit coated on a non-cooled substrate are boride. As deposit temperature increases, the coarsening of the precipitate particles results in lowered hardness of deposits.