Effects of tempering temperature on the microstructure and creep resistance of X22CrMoV12-1 steel used on steam turbine blades

Abstract

The development of manufacturing processes and materials for components of steam turbines are very important to increase the reliability and availability of power generation. These materials must have resistance to corrosion and creep, the effects of prolonged exposure to high temperature has a strong influence on metallurgical stability, causing them to fail in operation. Precipitation hardening stainless steels are thermally treated to improve their creep resistance through the formation of precipitates. The purpose of this study is to evaluate the influence of tempering temperature on the microstructure and the creep resistance of X22CrMoV12-1 steel. The microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Analysis of the tempered samples showed a microstructure composed of martensite with M23C6 carbides located along the martensite slats. Higher tempering temperatures promoted reduction of hardness, yield and ultimate tensile with increased elongation. The X22CrMoV12-1 tempered steel at 690°C showed superior performance of its creep resistance among tempered temperatures tested.