Microstructure and amorphization induced by frictional work in Fe-Cr-B alloy thermal spray coatings

Abstract

The microstructure and friction-induced amorphization of Fe-Cr-B alloy thermal spray coatings were investigated. Thermal spraying was carried out using a detonation gun with various fuel gas contents. The Fe-Cr-B alloy coatings were made up of Cr-rich boride particles embedded in the matrix of an Fe-Cr solid solution phase. Microstructural investigations using transmission electron microscopy (TEM) and Auger elemental analysis indicate that a friction-induced amorphization reaction occurs in the Fe-Cr solid solution phase which is supersaturated with boron. The boron concentration in the Fe-Cr solid solution phase may play an essential role in the stabilization of the amorphous phase formed by frictional work. The formation of oxide inclusions seems to impede the crystalline-to-amorphous transformation by reducing the boron concentration in the Fe-Cr solid solution phase. (C) 1999 Elsevier Science S.A. All rights reserved.