High temperature oxidation of transition metal carbide-containing iron matrices in high and low oxygen environments

The work on high temperature oxidation of transition metal carbide-containi ng iron-base alloys in high (pure O-2) and low oxygen (H-2-H2O) environment have been reviewed. Some studies carried out on high temperature (850-900 degreesC) oxidation of iron - base alloys containing dispersion of transiti on metal carbide illustrates the influence of mobility of carbon and stabil ity of carbide on the oxidation rates of the alloys. Ternary and quarternar y systems containing rare earth or refractory oxides show the influence of these additions in lowering the oxidation rates of the alloys by enhancing the adherence and compactness of the protective scales. In low oxygen envir onment, decarburization appears to be greatly influenced by the phase struc ture of the carbides. Alloys containing insoluble carbides show very low ra te of decarburization whereas those soluble in the matrix have high decarbu rization rates and generate well-defined decarburized. layer. The results o f oxidation behaviour of decarburized alloys are presented and are compared with corresponding undecarburized alloys, and the role of carbide dispersi on is emphasized.