Investigation of liquid impact erosion for 12Cr steel and Stellite 6B

Abstract

A study has been made on the liquid impact erosion mechanisms of 12Cr steel and Stellite 6B (Co–28Cr) currently used as steam turbine blade materials. 12Cr steel underwent the transition from ductile to brittle deformation behavior during liquid impacts. Damage started with the formation of isolated hollows. The increase in density and the overlapping of these hollows resulted in surface undulations with repeated impacts. The cumulative liquid impacts produced a work hardened surface, followed by the material loss due to crack formation and propagation. The deformation in Stellite 6B was especially governed by its microstructure. The carbide precipitates were selectively eroded while the precipitate–matrix interface and the precipitate interior acted as initiating sites for cracks. The damage of the cobalt matrix, where the mechanical twins were formed, was much lower than that of the carbide precipitates.