XRD and electron microscope study of a heat treated 26.6% chromium white iron microstructure

The microstructure of a 26.6% chromium white iron was characterised in terms of its phase constituents after being given a three stage heat treatment. The heat treatment cycle consisted of a 1-h anneal at 800 deg. C plus a 1-h destabilisation treatment at 1025 deg. C, followed by a subsequent 1-h temper at 450 deg. C. The heat treatment cycle used in the experiment was similar to that of a commercially used heat treatment. The use of XRD and electron microscopy has revealed that secondary carbides precipitated in the microstructural matrix of the white iron are of the form (Fe,Cr)23C6 and have a cubic crystal structure. The techniques have also shown that the matrix has transformed to martensite and has a 'c/a' ratio almost equal to unity