The Effects of Austempering Heat Treatment on the Mechanical Properties of Heavy Vehicles Camshaft made of Different Analysis Ductile Cast Iron

The aim of this study was to investigate the effect of the austempering treatment applied on ductile graphite cast iron with different chemical composition; microstructure, hardness, tensile strength and wear resistance. For this purpose sand mold casting models of camshafts were prepared and casting simulation was carried out with the NOVACAST program. The casting quality of camshafts and production process was optimized. For nodulizing process, Fe-Si-Mg alloy has been used and Fe-Si-Ba-Ca-Al alloy has been used for inoculation process. The casting has been done 1430 degrees C and the pouring time in 15 s. In different analyzes, a cast camshaft subjected to a 90 min austenitizing process at 900 degrees C under a mill vacuum furnace. The austenitized cam shafts have been quenched into the molten salt bath (50% KNO3 + 50% NaNO3) at 260 degrees C temperature, held for 30, 60, 90, 120, 150, 180 and 210 min and then cooled in air. Microstructures analysis of cam shafts have been examined by optical microscope and scanning electron microscopy (SEM), mechanical tests (hardness, tensile tests and wear tests) have been performed. Results show that austempering heat treatment increases the tensile strength of cam shaft as-cast condition. In this study, the tensile strength values of the austempered structure, camshaft core which has been formed in 120 minute duration which has the combination of excellent strength and ductility, have been brought from the level of 711.08 MPa to 1424.28 MPa.