The effect of heat treatment on microstructure and properties of a 13Cr6Ni2.5Mo supermartensitic steel

Abstract

The paper deals with studies how tempering/intercritical annealing in the temperature interval from 540 to 700°C affects mechanical properties and microstructure of a low carbon 13Cr6Ni2.5Mo supermartensitic steel. It has been proved taht during tempering at temperatures above 590°C partial austenitization is accompanied by intensive precipitation of Fe2Mo Laves phase in the martensitic matrix. Thermocalc calculations confirmed that Fe2Mo Laves phase is the thermodynamically stable phase in the steel investigated. Precipitation of Laves phase is probably responsible for the fact that a positive effect of the reversed austenite fraction on impact toughness was not observed. The fraction of reverted austenite in the microstructure increased up to the tempering temperature of 600°C.