Abstract
The present study investigates the effects of processing conditions on the tensile property and corrosion behavior of Incoloy-925. Grain refinement of the alloy can be achieved with both air hammer and Gleeble test. In addition, both yield strength and ultimate tensile strength at room temperature can be increased by controlling the size and volume fractions of L12 gamma-prime precipitates, and peak strength can be verified at the transition from strong-pair and weak-pair coupling models. However, significant hot ductility drop has been observed, experimental results show that the tensile strain has been decreased from 25 % at room temperature to 3 % at 650°C and fracture surfaces analysis has shown a ductile to brittle transition. Microstructure observations have revealed that primary gamma-prime phase along the grain boundaries can evolved into needle-like η phase at 650°C to cause hot ductility drop. Therefore, grain boundary engineering (GBE), which can change the distribution of grain boundaries, has been applied to Incoloy-925 to improve material properties. Experimental results indicate that effect of GBE doesn’t improve hot ductility drop a lot since there are a lot of η phases decorated along grain boundaries. However, increasing the aging temperature can homogeneously precipitate a great number of η phases, distributing uniform cracks over the bulk structure and increasing the hot ductility. Furthermore, corrosion behavior of Incoloy-925 has been investigated with salt spray test, polarization test, and oxidation test. Experimental results indicate that Incoloy-925 with and without GBE possesses good corrosion resistance. In addition, oxidation resistance with GBE is slightly improved.