Oxidation resistance of Ni+10% Cr alloy with additions of silicon, zirconium, hafnium, or rare earth metals

Abstract

1. Alloying of Ni-10% Cr with silicon along with small amounts of zirconium, hafnium, or REM leads to a sharp increase in the oxidation resistance of the alloy during isothermal and thermal cycling tests. 2. Small additions of hafnium, zirconium, lanthanum, or samarium to Ni-10% Cr-1.8% Si increase the time to failure several times in thermal cycling tests. The effect of these additions on the oxidation resistance of the alloy is negligible during isothermal oxidation, but increases with temperature in the range of 1000–1200°. 3. The increase in the oxidation resistance of Ni-10% Cr when alloyed with silicon along with zirconium, hafnium, or REM is due to formation of a protective layer of SiO2 in the scale and to good adherence of the scale to the alloy, ensured by precipitation of oxides of the second alloying element in the grain boundaries of the alloy beneath the scale.