Evaluation of using acetylene as carbon source in the carburization of steels

ABSTRACT The effect of using acetylene as a carbon source in the gas carburization of AISI/SAE 8620 steel was evaluated in this work. For this purpose, a gaseous carburizing system was designed and manufactured with the following characteristics: controlled production of a carburant gaseous atmosphere, inert and hermetic isothermal reaction zone and carbon/oxygen probe for the control of carbon potential (Cp) during the carburization cycle. An atmosphere composed of synthetic endothermic gas with composition of 40%H2, 40%N2 and 20%CO and constant flow of 100 cm3/min and acetylene variations with flows of 40cm3/min, 65cm3/min and 85cm3/min was used. These gases were injected into the reactor at 900°C and held for three hours. The acetylene gas was selected as the carbon-enriching agent in the atmosphere, due to the high decomposition ratios of these molecules and the low tendency to develop polymerization reactions. The characterization of the carburized steels was performed by optical microscopy (OM), optical emission spectrometry (OES) and Vickers microhardness tests (HV). The results show that there is a great efficiency and control in the carbon transfer during the carburization cycle, favoring the optimization of resources and processing times.