Influence of Quenching Medium on Microstructure, Hardness and Elevated Temperature Sliding Wear of 45C8 Steel

The aim of this study is to investigate the effect of heat treatment on microstructure, hardness and sliding wear of a medium carbon steel (45C8). The microstructure, hardness and high temperature dry sliding wear properties and behaviour of the as received and heat treated samples quenched in water and oil as quenching medium are investigated using the optical microscope, vicker hardness tester and high temperature pin on disc apparatus respectively. It is observed that the hardness of the water quenched specimens (760 HV0.5) is around 300% more than that of the parent metal (200 HV0.5) and it is 150% more than the oil quenched specimens (300 HV0.5). The microstructure shows hard martensitic structure on the outer surface of water quenched specimens whereas in oil quenched specimens, pearlite and acicular ferrite were observed. The wear test result showed an increased wear rate with increase in load. Furthermore, wear rate is lesser in water and oil quenched heat treated samples than that of the as received samples. The Scanning Electron Microscope (SEM) analysis of the wear scar indicates ploughing of the metal in as received specimen, while presence of oxides and fine micro cracks in oil and water quenched samples. This conventional heat treatment method increases the hardness and strength of the 45C8 steel, leading to enhanced load carrying capacity and wear resistance, which make them suitable for the industrial applications.