Surface Finish and Residual Stresses in Facing of Age Hardened INCONEL 718

Abstract

Facing although a major operation in aerospace industry, has not attracted much attention of researchers who have primarily investigated machinability related issues in longitudinal turning of INCONEL 718. This paper reports the results of investigation into the surface integrity of machined surface of age hardened INCONEL 718 parts in terms of surface finish and residual stresses while facing with PVD coated cemented carbide inserts of various geometries. The test results show that the residual stresses vary significantly under different machining conditions such as cutting data, coolant and cutting tool geometry. In most cases the residual stresses measured on the machined surface using XRD technique have tensile character. Residual stress history prior to the finishing operation and the coolant seem to play a major role and therefore the cutting data and other conditions even for roughing operations have to be carefully selected with the view to minimize the surface residual stresses prevailing after finishing operations.