Investigation of the High-Temperature Mechanical Property and Failure Analysis of GH2070P Alloy in Boiler Elbow Pipe

This study investigated the high-temperature (600 °C, 650 °C, 700 °C, 750 °C and 800 °C) mechanical property and failure analysis of GH2070P alloy in boiler elbow pipe. The results show that the microstructures of GH2070P alloy at three typical positions (outer radius (OR), middle radius (MR) and inner radius (IR)) of the bent pipe exhibit distinct gradient features to some degree, and the unsignificant difference in the morphology and composition of the second phase can be found in OR, MR and IR. Below 700 °C, the mechanical properties at different positions show differences affected by the stress states of different positions. Among them, the tensile strength and yield strength of OR under tensile stress states are lower than those of IR under compressive stress states at the same temperature. However, above 700 °C, the mechanical properties of the three positions show no significant difference, which is related to stress release at high temperatures. From 700 °C to 800 °C, the degree of brittle fracture of the material increases, which is related to the performance degradation caused by the coarsening of the second phase at high temperatures. It is worth noting that within the temperature range of less than 700 °C, the yield strength increases with the rise in temperature, while the tensile strength and plasticity remain at a certain level without decreasing. This indicates that the GH2070P alloy has good service performance at 700 °C.