Screening and evaluation of materials for microturbine recuperators

The effects of stress, temperature and exposure to microturbine exhaust gases on the mechanical properties and corrosion resistance of candidate materials for microturbine recuperators were investigated. Results are presented for 347 stainless steel metallic foils after 500-hr exposure to temperatures between 620°C and 760°C at a tensile stress of 50 MPa. It was found that the material experienced accelerated attack at the highest temperature and that the corrosion products consisted of mixed oxides of iron and chromium. It was also found that exposure at the highest temperatures resulted in significant decrease in both tensile strength and ductility. ORNL's microturbine recuperator test facility, where the exposures were earned out, is also described.