Influence of hot deformation parameters on the tensile properties of VDM Alloy 780

Ni based superalloys are prominent candidates for aerospace applications to be employed under demanding conditions. Emerging new technologies to improve engine efficiency and reduce environments footprint require alloys that can withstand severe conditions and higher temperatures. VDM Alloy 780 offers a diversity of properties, namely microstructure uniformity, high oxidation resistance and good mechanical properties up to 700°C as well as weldability and good hot workability, making it a suitable candidate for aerospace applications. Depending on the application, grain size following forging process should be controlled to meet the required mechanical properties and operational lifetime. Grain size and precipitation of gamma’ and eta/delta phases during and following hot deformation is the direct consequence of the recrystallization, grain growth and precipitation kinetics. In this work, the influence of forging temperature and heat treatment on the microstructure and tensile properties are studied. Two different forging temperatures (950°C and 1050°C) are used to generate microstructures in subsolvus and supersolvus domains, respectively, leading to full recrystallization and grain coarsening in supersolvus domain. The subsequent heat treatment helps to achieve a uniform distribution of gamma’ precipitates, at which delta phases only appear to be present to a small extent. This determines the mechanical properties particularly the tensile strength and elongation at rupture. Tuning the grain size and gamma’ precipitations with a unique processing route could improve the mechanical properties of VDM Alloy 780, making it suitable for high performance applications.