Surface Integrity in Conventional Machining

Abstract

Metal removal processes disturb or alter the surface layer creating characteristics which may be quite different from those of the base metal. A wide variety of surface alterations can be produced by conventional machining as well as by a variety of electrically and chemically assisted metal removal methods. The effect of variables in milling and grinding will be reviewed. Photomicrographs illustrating surface alterations produced in martensitic steels, titanium and nickel alloys will be presented, as well as microhardness data illustrating the types of hardness changes found in these surfaces. Data on residual stresses produced in some of these materials as a function of machining variables will also be presented. The fatigue characteristics of these alloys, as affected by conventional metal removal process variables, are summarized and explained. It can be concluded that the method of machining and the variables chosen for a particular machining method are significant in relation to the mechanical performance of finished parts. Machining methods must, therefore, be carefully evaluated in their relation to the performance of highly stressed components which are subjected to a variety of hostile environments.