Influence of secondary carbides precipitation and transformation on hardening behavior of a 15 Cr–1 Mo–1.5 V white iron

Abstract

The influence of secondary carbides precipitation and transformation on hardening behavior of a 14 Cr–1 Mo–1.5 V white iron in sub-critical treatment was studied by using optical microscope (OM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Results show that two hardening peaks appeared in the process of sub-critical treatment at 833 K, and the reasons for the two hardening peaks are different. In sub-critical heat treatment, Martensite transformation and (Fe,Cr) 23C 6 precipitation from austenite matrix, which harden the alloy, are responsible for the first hardening peak. MoC and (Cr,V) 2C precipitations and/or transformation from M 23C 6 causes the secondary hardening peak. Furthermore, the in situ transformation of (Fe,Cr) 23C 6 to M 3C carbide causes the formation of pearlite and an associated decrease of the bulk hardness.