THE EFFECT OF ALLOY COMPOSITION ON THE PERFORMANCE OF STAINLESS STEELS IN EXHAUST GAS ENVIRONMENTS

摘要

Recuperators for developmental high-efficiency small gas turbine engines will require low-cost materials with both creep and corrosion resistance at 700 deg C or higher. Because of the accelerated corrosion attack caused by water vapor in the exhaust gas and pressurized inlet air, alloys used in current recuperators, such as type 347 stainless steel, do not have sufficient oxidation resistance to meet lifetime goals at these higher temperatures. More highly alloyed steels and Ni-base alloys can meet the requirements but may be prohibitively expensive. Model Fe-Ni-Cr and Fe-Cr alloys are being tested in air plus 10 percent water vapor in order to determine compositions with appropriate environmental resistance for this application and to determine the effect of minor alloy additions. Results indicate that Ni and Cr contents in the 20wt. percent range prevent accelerated attack observed in leaner alloys and that Si is the most critical minor (<0.5 wt. percent) alloy addition for long-term oxidation resistance in these environments.