Microstructural characterization of Haynes® 242™ alloy

A microstructural characterization has been performed on a HAYNES 242 nickel-molybdenum-chromium superalloy. Molybdenum was found to partition to the lenticular Ni2(Mo,Cr) precipitates whereas iron, aluminum, silicon, manganese and nickel were found to partition to the γ matrix. Chromium was not found to partition significantly between the phases. Atom probe tomography and energy-filtered transmission electron microscopy core-loss images revealed boron, molybdenum, chromium, phosphorus and carbon segregation to the grain boundaries. Despite the size of the precipitates being larger after a two-step heat treatment of 16 h at 704 °C+16 h at 650 °C compared to a one-step heat treatment of 48 h at 650 °C, no significant differences were found in the mechanical properties or the compositions of the phases.