Performance of Oxidation and Creep Resistant Alloys for Primary Surface Recuperators for the Mercury 50 Gas Turbine

Abstract

Recuperation is a means for increasing the efficiency of a simple-cycle gas turbine, allowing for heat transfer between the exhaust and compressor discharge gas streams to occur in a highly efficient, relatively compact package. The primary surface recuperator operates at high temperatures and gas pressures and is constructed from thin metal sections, presenting challenges for high temperature materials selection. This paper discusses a joint Solar Turbines-ATI Allegheny Ludlum project which was undertaken to address the issue of elevated temperature attack in the presence of high levels of water vapor and its relevance to alloys intended for use in primary surface recuperators. An overview of the alloy selection process will be presented, followed by a detailed study of the two most promising alloy candidates. Breakaway oxidation was mitigated by using alloys with higher nickel and chromium content, and oxide scale evaporation was controlled with selected minor element additions.