Rapidly solidified nonequilibrium microstructure and phase transformation of laser-synthesized iron-based alloy coating

摘要

The rapidly solidified microstructural and compositional features, the precipitation and transformation of carbides during tempering, and the impact wear resistance of an iron-based alloy coating prepared by laser cladding are investigated. Theclad coating alloy, a powder mixture of Fe, Cr, W, Ni, and C with a weight ratio of 10:5:1:1:1, is processed using a continuous wave CO{sub}2 laser. Microstructural studies demonstrate that the coating possesses the hypoentectic microstructure comprisingthe primary dendriticγ-austenite and interdendritic eutectic consisting ofγ-austenite and M{sub}7C{sub}3 carbides. γ-Austenite is a non-equilibrium phase with an extended solid solution of alloying elements. During high temperature tempering at 963 Kfor 1 h, the precipitation of M{sub}23C{sub}6, MC and M{sub}2C carbides in austenite and in situ carbide transformation of M{sub}7C{sub}3 to M{sub}23C{sub}6 and M{sub}7C{sub}3 to M{sub}6C respectively are observed. In addition, the microstructure of thelaser-clad coating reveals an evident secondary hardening and a superior impact wear resistance.