Mechanism of σ-phase precipitation in Cr–Ni austenitic steels

Abstract

The mechanism of σ-phase precipitation in industrial Cr–Ni austenitic steels has been found to depend on the chemical composition of the austenite after precipitation of the interstitial phases whose formation always precedes nucleation of the σ-phase. Depending on the chemical composition of the austenite, the σ-phase may precipitate directly from the austenite and partially through the M23C6 carbide or through the ferrite, or only through the M23C6 carbide. In this last case the quantity of σ-phase precipitated does not exceed 0·5%.MST/529