Investigation of the Heat Treatment Process and Formation Mechanism of Grain Boundary Serration for GH4795 Superalloy

Abstract

Heat treatments, including solution treatment and isothermal heat treatment, were conducted to investigate the grain boundary serration of GH4975 superalloy. The two different heat treatment processes could both promote the formation of serrated grain boundaries within the present temperature and soaking time ranges, provided that the cooling rates were controlled to be quite slow. The samples subjected to furnace cooling exhibited a more obvious serrated grain boundary morphology by comparison with those subjected to air cooling. The interaction between precipitated phases and grain boundaries was focused to explore the formation mechanisms of serrated grain boundaries within GH4975 superalloy. Heat treatment temperature and soaking time strongly affected the morphology and size of precipitated phases, and consequently influenced the formation of serrated grain boundaries. The directional growth of grain boundary precipitates and its pinning effects on the migration of grain boundaries also affected the grain boundary morphology.