Microstructure analysis of P91 heat resistant steel in service for 3 years

P91 heat resistant steel is an important material for supercritical units. In this paper, a P91 heat resistant steel pipe which has been used for about 3 years is analyzed by means of hot tensile test, metallography and scanning electron microscope. The results show that the microstructure is martensite and a large number of Cr-rich precipitates are distributed at the grain boundary. There are pores and cracks in the fracture of high temperature tensile specimen.