Designers of high-temperature power generation plants, both nuclear and fossil-fired, have made extensive use of 2 1/4 Cr--1 Mo steel for piping, shell, and tubing and as a tubesheet material in steam generators. While this material has been researched as much if not more than any other boiler material, an understanding of the time-dependent fatigue behavior for long-term service applications is still incomplete. Progress is reported in obtaining formulations that can be used for low and high cycle continuous cycle fatigue, time-dependent fatigue, and crack growth behavior. Material variables such as melting practice, heat-to-heat, and heat treatment variations are discussed. The importance of environment is shown by comparing the results of elevated-temperature strain and load-controlled tests of different waveforms conducted in both air and helium. Interim progress is reported in characterizing the crack growth behavior of HAZs adjacent to dissimilar weld joints of this material
