Anomalous Segregation Kinetics of Phosphorus and Carbon Governed by Carbide Reactions in 2.25Cr-1.5W Heat-resistant Steel

Abstract

In a 2.25Cr-1.5W heat-resistant steel containing V and Nb, the formation sequence of carbides are detailed. Such carbide reactions determine directly the anomalous segregation kinetics of phosphorus and carbon at the grain boundary/carbide interface. The anomalous segregation kinetics of phosphorus consists of two maximum segregation peaks and one minimum peak corresponding to the high segregation concentration of carbon. The roles of the carbide reactions on the anomalous segregation kinetics of the solutes are fully understood from the viewpoint of the dissolution of unstable carbides into the matrix for forming the stable carbides, the active segregation of the dissolved carbon into the newly formed carbide interface for the growth and the resultant repulsive segregation between carbon and phosphorus.