Effect of Alloying Additions on the Oxidation of High Speed Steels under Dry and Wet Conditions

An investigation has been carried out into the effects of chromium and vanadium content on the oxidation rate and on the adhesion of oxide scales grown on three different chemical compositions of high speed steels under dry and wet conditions. The oxidation tests were carried out in a thermobalance at 650 ℃ for up to 14.4 ks. The mass gain of the specimens increased with increasing contents of water vapour. Alloy composition had no effect on the oxidation rate in dry conditions. The "adhesion" of the oxide scale was determined using indentation with a Rockwell C diamond and the pull adhesion test to determine the interfacial toughness and the tensile strength of the oxide metal bond, respectively. Generally, the results of the investigation indicated that oxide adhesion was lowest for the specimens exposed to dry conditions, and that with increasing water vapour content, the scale was more adherent. Indentation test results showed that an increase in the Ⅴ concentration was deleterious to oxidc adhesion in both the dry and wet environments, whereas an increase in the Cr-content had little effect on adhesion.