The effects of austempering and induction hardening on the wear properties of camshaft made of ductile cast iron

Abstract

The aim of this study is to investigate the effects of heat austempering and induction hardening on the wear properties of GGG60 ductile cast iron for camshaft production. For this purpose, camshafts have been produced by sand mould casting method. Fe-Si-Mg alloy has been used for inoculation process to achieve iron nodulization. The casting has been done between 1410-1420°C. The casted camshafts have been austenitized at two different temperatures (800 and 900°C) and time intervals (60 and 90 min) under controlled furnace atmosphere. The austenitized camshafts have been quenched into the molten salt bath at 360°C, held there for 90 min and then cooled in air. This way, austempering heat treatment has been applied. After that, surface hardening process was conducted using induction hardening machine with medium frequency. Microstructure of camshafts has been examined by optical methods and mechanical tests have been performed. Results show that austempering heat treatment increases the wear resistance of camshaft, compared to as-cast condition. Wear resistance of the camshaft increases with increasing austenitizing temperature, time and with induction hardening. The lowest weight loss of 0.62 mg has been obtained for the induction hardened camshaft austenitized at 900°C for 90 min.