Microstructural characteristics of forged and heat treated Inconel-718 disks

Microstructure evolution from center to edge of the as-forged and heat treated Inconel-718 disks was investigated. Specifically, the evolution of primary carbides, grain size, γ″, γ′, δ, and secondary carbide particles was the focus of the current study. In fact, characterization of these microstructure features is essential for models predicting the creep and fatigue lives of the alloy. Accurate and reliable revealing of the grain boundaries in as-forged and heat treated Inconel-718 was made possible in this study by development of a new method. From microstructure investigations, nonuniformities in grain size, volume fraction, size and inter particle spacing of precipitates from center to edge were observed in both as-forged and heat treated disks. The microstructure nonuniformities resulted in significant variation in hardness from center to edge of the disks.