Comparative study of finishing techniques for age-hardened Inconel 718 alloy

Inconel 718 is a widely used alloy in the aeronautic sector due to its excellent mechanical and corrosion wear resistance under high temperature conditions. However, its good mechanical properties can be a double edge sword in terms of manufacturing, especially in those processes based in mechanical principles, such as machining or forming. Considering that most aeronautic components are exposed to cyclic load and temperature, fatigue resistance becomes critical, and therefore, the finishing processes. The surface integrity of a component plays an important role on its fatigue behaviour, as the most common crack initiation area is usually the surface. The present work compares three different mechanical finishing processes that confer better surface properties to the component: polishing, burnishing, and hammer-peening. Each one achieves different degrees of roughness, and residual stress on the surface. The study is not only focused on the resultant mechanical properties, but also in productivity and process robustness. It is concluded that each technology excels in a different property.