Effects of Silicon Content and Oxidation Potential on the Carburization of Centrifugally Cast HK-40

The presence of stable oxide scales has been shown to retard the carburization of heat resisting alloys at high temperatures. In particular, Schnaas and Grabke (1) demonstrated that chromia produced on an alloy exposed to a carburizing-oxidizing environment provided a barrier to carbon transport while the scale remained intact, and that carburization occurred when the scale was ruptured in creep. The temperature dependence of carbon pick-up in some pack carburization tests has also been related to the stability of chromium oxide by Grabke et al (2). Alumina scales have been found to be stable in strongly carburizing gases (3) and preformed aluminum oxide has been shown to be protective against carburization (4).