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

The microstructure and friction-induced amorphization of Fe-Cr-B alloy ther mal spray coatings were investigated. Thermal spraying was carried out usin g a detonation gun with various fuel gas contents. The Fe-Cr-B alloy coatin gs 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 fri ction-induced amorphization reaction occurs in the Fe-Cr solid solution pha se which is supersaturated with boron. The boron concentration in the Fe-Cr solid solution phase may play an essential role in the stabilization of th e amorphous phase formed by frictional work. The formation of oxide inclusi ons seems to impede the crystalline-to-amorphous transformation by reducing the boron concentration in the Fe-Cr solid solution phase. (C) 1999 Elsevi er Science S.A. All rights reserved.