THE INFLUENCE OF HEAT TREATMENT ON MICROSTRUCTURE AND THERMAL PROPERTIES OF C45 TOOL STEEL.

In this paper, C45 medium carbon tool steel was investigated after various heat treatments. The thermal properties, specifically thermal diffusivity and thermal conductivity, were measured and also the microstructure analysis was done on a light microscope. Heat treatment of the samples included: 1) the normalization heat treatment at 900°C for one hour and cooling in the air; 2) quenching the samples in water and in oil separately after reheating them at 880°C for one hour and; 3) tempering the quenched samples at 200°C-350°C for 2 hours. The results show the highest values of thermal properties for the normalized sample. Also, the lowest values were recorded for the quenched samples, and the values of thermal properties for the tempered samples are between the values of the quenched and normalized samples. Microstructure analysis shows a typical ferrite-pearlite structure after normalization. Martensite appeared in the water-quenched sample. However, the microstructure of the oil-hardened sample predominately consists of ferrite and pearlite because the critical cooling rate was not reached. Tempered samples quenched in the water had the microstructure of tempered martensite. [ABSTRACT FROM AUTHOR]