Microstructural evolution with varying solutionizing temperature in Allvac 718Plus

Alloy Allvac 718Plus is relatively new superalloy developed to improve the properties of the widely-used superalloy Inconel 718. It shows improvement in service temperature up to 704ºC (55ºC more than IN718) because of its chemical composition, microstructure and major strengthening phase, γ’. The high temperature stability of the microstructure influences the life and mechanical properties of these alloys. Therefore, it is necessary to understand the phase evolution as a function of temperature. In the present work, the solutionizing temperature has been varied during heat treatment which led to varied grain size and phase volume fraction. The as-received samples were solution annealed at 1100ºC, 1050ºC, 1000ºC, and 954ºC followed by aging at 788ºC for 8 hour then furnace cooled to 704ºC for 8 hr (two-step ageing). Metallographic samples of the as-received and heat treated samples were prepared to identify different phases using optical microscopy and scanning electron microscopy (SEM). Electron Backscatter Diffraction and Energy dispersive spectroscopy was performed to investigate the composition of the various phases. All the data obtained were rationalized and compared with the existing data. This data will help in investigating the dependency of time and temperature on the microstructural changes.