Influence of Flow and Pressure of Carburising Mixture on Low-Pressure Carburising Process Efficiency

Abstract

Low-pressure carburising (LPC) of steel is an industrially accepted method for improving the properties of a steel surface. LPC is environmentally friendly, does not cause intergranular oxidation and consumes less energy. Its effectiveness depends on the correct choice of process inputs. This paper aims to determine the effect of this type of carboniferous gas, pressure and flow rate on the efficiency of carbon transfer to the surface layer under low-pressure carburisation. A total of 40 disks of 16MnCr5 steel were carburised using pure acetylene or a mixture of acetylene, ethylene and hydrogen as a carboniferous gas, pressures of 2 or 6 hPa and two gas flow rates. The specimens were gravimetrically tested for the increase in the mass of carbon in the carburised layer. The results were analysed with U Mann–Whitney analysis and t-Student test. It was evidenced that carburising with pure acetylene resulted in a higher increase in carbon mass than carburising with the mixture (p < 0.05). Pressure and gas flow rates are important for carburising efficiency (p < 0.05).