Effect of Pt Additions on the Sulfur Segregation, Void Formation and Oxide Scale Growth of Cast Nickel Aluminides

摘要

The addition of Pt in cast and diffusion nickel aluminide is known to improve the oxide scale adhesion, but the positive effects of this element remain still imprecise. This present study reports experimental results concerning the diminution of sulfur segregation in the presence of platinum (10% at.) in β-NiAl, at 750℃. However, Pt did not completely prevent sulfur from segregating to a free surface. It was also shown that the addition of Pt in the alloy decreased the formation of voids at the oxide/metal interface after isothermal oxidation at 900℃. The ratio of the oxide thickness to cavity depth strongly decreases in Pt modified nickel aluminide. Lastly, thermogravimetric investigations revealed that Pt increased the oxide growth rate at 1100℃.