Quantitative characterization of surface damage to WC-cobalt composites by electrochemical grinding

Abstract

Electrochemical grinding (ECG) of WC-cobalt cemented carbides leads to poor surface quality which can be attributed to the faster electrochemical dissolution velocity into the cobalt phase than into the carbide phase. A method for measuring the degree and depth of damage in the WC-cobalt surface layer, weakened by preferential electrochemical removal of cobalt after ECG, is developed based upon an analysis of the mechanical grinding transient which occurs after switching off the electrical current for ECG. The degree of weakening is expressed as the ratio of the specific grinding energy of the material in the surface layer to the normal specific grinding energy. It is found that surface damage from ECG can reduce the specific grinding energy by as much as a factor of 10 at the finished surface, and that the depth of the damaged layer is shallower with a lower current density and a faster infeed velocity.