Surface Hardening of Non-ferrous Metals by Spark Discharge

Abstract

AN earlier communication¹ from this Laboratory described experiments in which the thermal action of electric sparks was used to simulate the effects of frictional heating on the structure of rubbing steel surfaces. The high local temperatures which characterize rubbing contacts can, in certain circumstances, initiate austenite formation and, since conduction into the bulk metal provides effective quenching of the hot spots, martensite is formed and causes hardening of the surface layer. Similarly the brief but intense heat of an electric spark, struck between an electrode and the steel surface, can harden a small volume of material. If the sparking electrode traverses the surface a hard and wear-resistant skin develops.