The Cathodic Electrolytic Plasma Hardening of Steel and Cast Iron Based Automotive Camshafts

Cathodic electrolytic plasma hardening is a novel thermochemical surface modification and hardening process, used to increase wear resistance and surface hardness of metallic components in a local area of interest. The heating efficiency is related with the plasma nozzle design, applied current and electrolyte. The nozzle design is also a critical factor for the hardening of complex shapes, such as gears and camshafts. In this work, lobes of camshafts, fabricated from several cast iron and steel grades were hardened by cathodic electrolytic plasma hardening in aqueous carbonate electrolyte, using a specific plasma nozzle. The camshafts were attached to CNC lathe for turning them in the horizontal axis. In order to optimise heating and to achieve the ideal flowing and wetting by the electrolyte of the lobe case, the ceramic ellipse-shaped nozzle outlet was designed. As a result of preliminary studies, external surface of lobes was heated and subsequently quenched by electrolyte. The hardness of processed surface was in the range of 50-60 HRc for the different camshafts. No distortion was observed on the surface of lobes. Hardness depth was measured to be from 0.1 mm to 5 mm for several lobes.