In situ SEM study on tensile deformation behavior of forged Inconel 718 turbine disk at elevated temperatures

The hub and web of turbine disk generally work below 600 °C and are prone to fatigue deformation. However, the rim typically operates at temperatures ranging from 550 to 700 °C, even occasionally exceeding 800 °C. Thus, the present study aims to investigate the tensile deformation behaviors of the rim region of Inconel 718 alloy turbine disk in the range of 650–850 °C, using an in situ high-temperature tensile stage. The results indicate that temperature has different effects on the tensile deformation behavior of alloy. The in situ observations revealed that the deformation at 650 °C was dominated by crystal slip. The microcracks mostly initiated near non-metallic inclusions (NMIs) and propagated in transgranular manner. Intergranular cracking appeared at 750 and 850 °C, but did not coalesce to form continuous intergranular cracks. Fractographic analysis demonstrated that the fracture mode was transgranular ductile fracture for the three temperatures. The voids on the fracture surface evidenced that the cracking and debonding of NMIs were the origins of most macroscopic cracks of the specimens. This study provided direct experimental evidence for revealing the deformation and damage mechanisms of the rim region of turbine disk at service temperature.