Surface machining condition and fatigue life on Inconel 718

Abstract

Life assessment of components working in aero-engines at elevated temperatures is critical. Machining has a serious effect on these nickel-based alloys, for example in turbine discs, affecting their life in service. Machining (turning, broaching…) modifies surface roughness, thickness of the affected substrate layer (including the effect of possible broken carbides) and residual stress distribution near the component surface. On top of that, it is possible to shot-peen or not the component, which again modifies its surface integrity. The aim of this work is to discern among the effect of the different parameter: roughness, damage and residual stresses on fatigue performance and optimum machining conditions.