IJPEM

Inconel 718 superalloy controlled surface integrity for fatigue applications produced by precision turning

Hamid Javadi/Ecole de Technologie Superieure

KEYWORDS: Precision turning, Inconel 718, Fatigue design, Surface integrity maps

An original approach is introduced to discriminate the effects of residual stress and surface roughness on turned Inconel 718 alloy parts. This could be used for assessing or studying the performance of these specimens during fatigue tests. This method consists of building surface integrity maps in terms of surface roughness parameters and residual stress in order to select specific turning conditions with adequate machining parameters. The surface integrity maps were generated by using response surface methodology based empirical models and precision turning tests on coupons. The proposed approach was therefore successfully applied to manufacture rotating bending fatigue specimens with the surface axial residual stress varying from − 239 to 446 MPa while keeping the arithmetic average roughness and the surface hoop residual stress constant. The effect of the surface axial residual stress on the fatigue life could thus be discriminated from the other surface integrity characteristics effects. The proposed methodology is independent of the manufacturing process and can be extended to other machining processes such as milling, grinding, and broaching.