محمد دهقان

The purpose of this research is to achieve the nano-fine microstructure and investigate the effect of austempering conditions in order to improve the impact energy of 8CrMnMo100 steel. Based on this, it was tried to eva‎luate the impact energy of this steel after the austempering process by modifying the 8CrMnMo100 alloy with silicon, cobalt and aluminum alloy elements and investigating the effect of austempering temperature and time. For quantitative and qualitative eva‎luations, the phases in the microstructure were identified by optical microscope, scanning electron microscope, and X-ray diffractometry, and the residual austenite volume fraction, carbon content in the residual austenite, and the average thickness of the binite ferrite plates were calculated. Vickers hardness tester was used to find out the effect of temperature and isothermal operation time on the hardness of the samples. Finally, after performing the impact test and measuring the impact toughness, the fracture surface of the samples was recorded using a field emission scanning electron microscope. In this research, it was shown that by adding 1.5% by weight of silicon, 1% by weight of aluminum, and 1% by weight of cobalt to the 8CrMnMo100 alloy, it is possible to prevent the precipitation of transition carbides, increase the carbon content of the remaining austenite, and reduce the thickness of the binite ferrite plates, causing an increase of approx. The impact energy of this steel was doubled after austempering. Finally, the highest amount of impact energy for the sample obtained at the austempering temperature of 250°C for 24 hours was 16.5±0.2 J. This amount of impact energy is obtained from the microstructure that consists of 83.7% bainitic ferrite with an average plate thickness of 62±8 nm surrounded by residual austenite films with a carbon content of 1.74% by weight and has a hardness of 515±6 HV30.

فولاد 100CrMnMo8 , نانوساختار بينايتي , دما و زمان آستمپرينگ , كسرحجمي آستنيت باقيمانده

100CrMnMo8 steel , nanostructured bainitic steel , austempering time and temperature , volume fraction of retained austenite

Mohammad Dehghan

Prof. Saeed G. Shabestari - Dr. Seyed Hossein Razavi