Evolution of grain boundary chemistry in a Ni–17Cr–9Fe model alloy

The evolution of grain boundary microchemistry of a nickel base alloy has been studied using atom probe field ion microscopy (APFIM), secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The investigated material was a high purity model alloy with composition Ni–17.0%Cr–8.9%Fe–0.12%C–0.03at.%B. After solution annealing at 1100°C for 20 min all carbon and most of the boron was in solution. Intergranular chromium-rich borides, probably formed during quenching, were observed. Subsequent heat treatment at 700°C, for 6 min–20 h, resulted in precipitation of intergranular Cr7C3 and Ni23B6. After 100 h, nickel-borides were not present.