Oxidation-Sulfidation Behavior of Ni Aluminide in Oxygen-Sulfur Mixed-Gas Atmospheres.

摘要

Oxidation-sulfidation studies were conducted with sheet samples of nickel aluminide, containing 23.5 at. % Al, 0.5 at. % Hf, and 0.2 at. % B, in an annealed condition and after preoxidation treatments. Continuous weight-change measurements were made by a thermogravimetric technique in exposure atmospheres of air, a low-P/sub O sub 2 / gas mixture, and low-P/sub O sub 2 / gas mixtures with several levels of sulfur. Corrosion product scale layers were analyzed. Air-exposed specimens developed predominantly nickel oxide; the specimen exposed to a low-P/sub O sub 2 / environment developed an aluminum oxide scale. As the sulfur content of the gas mixture increased, the alumina scale exhibited spallation and the alloy tended to form nickel sulfide as the reaction phase. Results indicated that the sulfidation reaction of nickel aluminide specimens was determined by the rate of transport of nickel from the substrate through the scale to the gas/alumina scale interface, the mechanical integrity of the oxide scale, and the H sub 2 S concentration in the exposure environment. 6 refs., 8 figs., 3 tabs.