Carbide precipitation and the reversion of martensite to austenite in a semi-austenitic stainless steel

Abstract

Carbide precipitation processes in austenitic samples of an Fe–15Cr–81/2Ni–2Mo-o·09C semi-austenitic stainless steel at 700°C have been studied by measurements of hardness, saturation magnetic intensity and by electron microscopy. The austenitic structures wereproduced by a 1250°C solution treatment or by rapid heating of partially martensitic structures to produce ‘reversed austenite’; the martensite wasformed either by refrigeration below the Ms temperature or by cold rolling at room temperature. Carbideparticles, often identified as M₂₃C₆, were observed to form in several morphologies. Some regions of martensite formed from the alloy-depleted matrix on cooling to room temperature after aging. Long aging treatments resulted in partial transformation of the austenite matrix to ferrite by a diffusional process.