The effect of cerium on the oxidation resistance of Fe -20Cr-1.7C-lSi

Abstract

Co is the major contributor to the radiation build-up in nuclear power plants. Many studies have been done to develop Co-free hardfacing alloys to replace Co-based Stellite 6 which is used for valve hardfacing. The Co-free alloys should have equivalent wear resistance, cavitation erosion resistance, and oxidation resistance to Stellite 6. Recently, we developed Fe-20Cr-1.7C-lSi alloy to replace Stellite 6. The new alloy has equivalent sliding wear resistance, and cavitation erosion resistance to Stellite 6. However, the high temperature oxidation resistance of the Fe-based hardfacing alloy is not as good as much as that of Stellite 6 due to the Cr deficiency in the Fe-based hardfacing alloy matrix. Ce is known to improve oxidation resistance of Fe-based alloys at elevated temperatures due to the beneficial effects of Ce such as formation of fine oxide layers and reduction of oxide-growth stresses. Therefore, in present study, the effect of Ce on the oxidation resistance was investigated in pressurized-water at 300? under 7 MPa for 200 days in an autoclave. The concentration range of Ce was up to 0.2 wt.%. The specimens containing 0.2 wt.% Ce showed lower weight loss compared to that of the Ce-free specimen. With increasing Ce concentration, high temperature oxidation resistance of new alloy increased. The increased high temperature oxidation resistance may be due to the formation of adhesive oxide layers.