Micro characteristics and macro performance of HR3C/T92 steel joints after 100000 hours service at high temperature

Abstract

In this study, HR3C/T92 dissimilar steel joint samples were taken from ultra-supercritical 1000 MW units of domestic power plants, and the microstructures, tensile property, hardness, and antioxidant performance as well as safety assessment of the welded joints were studied using OMR, SEM, UTM, and other equipment. The results reflected that the micromorphology characteristics and hardness of HR3C/T92 dissimilar steel joints are unaffected after 100000 hours of service. Nevertheless, tensile and impact tests revealed that the joints are prone to brittle fracture. Tensile fracture occurred on the weld fusion line of T92 steel, and the impact absorption energy was lower than the standard requirements. HR3C steel exhibited superior oxidation resistance and corrosion resistance. Moreover, there was no observable oxide layer on the inner wall of the pipe, and the outermost layer of the outer wall had an intact structure. The inner wall of the T92 steel pipe had a 300-μm-thick oxide layer comprising Fe2O3 and (Fe, Cr) oxides. The extrapolated performance of the dissimilar steel joint samples after operation for 200000 hours at high temperatures also met the service requirements.