Microstructure and mechanical properties of T92 and 310HCBN tubes for 1000 MW ultra-supercritical boilers

Taking a 1000 MW ultra-supercritical boiler heating surface pipe as the research object, the microstructure and mechanical properties of T92/TP310HCbN secondary reheater pipe and its welded joints after its service for about 60, 000 h were analyzed. The deterioration degree of the two materials and welded joints after long-term service was studied. The results show that the microstructure of welded joints and base materials of T92/TP310HCbN steel is normal and no obvious aging phenomenon is observed after high-temperature service. In terms of mechanical properties, the yield strength and tensile strength of the two kinds of steel pipe welds meet the standard requirements, but the elongation of TP310HCbN steel pipe after fracture decreases obviously, indicating that its brittleness increases. In addition, the hardness value of the coarse crystal zone on the side of T92 steel is high, and the metal supervision in this area should be strengthened to ensure the safe operation of dissimilar steel welded joints under long-term high temperatures and high pressures.