On the heat treatment of Rene-80 nickel-base superalloy

Rene-80, as an alloy for production of the jet turbine blades, shows high mechanical properties as well as microstructure stability during the high temperature engine operation. In this study we tried to have a deep insight on the microstructure of the cast Rene-80 and the evolution of microstructure during the different stages of the relatively complex GE class-A heat treatment. Although the solution heat treatment homogenized the chemical alloy segregation resulted from the casting to some extent, it did not cause all the casting γ′ particles to dissolve completely in the matrix. Primary aging caused growth in the residue particles as well as growth of the new precipitated particles, which have been nucleated during cooling after solution heat treatment. Stabilization stage involved further growth of the cubic γ′. Aging, as the last stage of the heat treatment, led to the final growth of the cubic γ′ and introduced the secondary spherical γ′ particles in the corridors of the primary cubic γ′ precipitates as well as M23C6and M6C carbides formation. Serrations in the grain boundaries, which has the well-known positive influence on the creep crack propagation at high temperatures, formed during the controlled cooling stage after the solution heat treatment and primary aging.