The γ→α Transformation and Carbide Precipitation of 2Cr and 9Cr Steels

Abstract

The γ→α transformation and the carbide precipitation in 2Cr and 9Cr steels were investigated by using optical and electron microscopy. In the 2Cr steel, the proeutectoid ferrite was observed at early stages of transformation, while the lamellar structure with α and cementite was observed at later stages around the nose temperature. In the 9Cr steel, the eutectoid structure composed of α and M₂₃C₆ were observed from early stages of transformation. Above the nose temperature, α and M₂₃C₆ appeared as a lamellar structure. Below the nose temperature, carbides were aligned in ferrite. Factors affecting the rate of the γ→α transformation and the morphology of carbide precipitation are discussed in this paper.