Selecting and Developing Advanced Alloys for Creep-Resistance for Microturbine Recuperator Applications1

Abstract

Recuperators are considered essential hardware to achieve the efficiencies desired for advanced microturbines. Compact recuperator technologies, including primary surface, plate and fin, and spiral, all require thin section materials that have high-temperature strength and corrosion resistance up to 750°C or above, and yet remain as low cost as possible. The effects of processing and microstructure on creep-rupture resistance at 750°C and 100 MPa were determined for a range of austenitic stainless alloys made into 0.1-mm foils. Two groups of alloys were identified with regard to improved creep resistance relative to type 347 stainless steel. Alloys with better creep-rupture resistance included alloys 120, 230, modified 803 and alloy 740 (formerly thermie-alloy), while alloy 214 and 625 exhibited much better creep strength. Alloys 120 and modified 803 appeared to have the most cost-effective improvements in creep strength relative to type 347 stainless steel, and should be attractive for advanced microturbine recuperator applications.