Manganese Volatilization and Its Influence on Low-Pressure Carburizing Process Effects

The presented research quantitatively characterizes the depth and fraction of Mn volatilization under LPC conditions for the first time and its influence on surface layer properties. It has been proven that this phenomenon increases with holding time at carburizing temperature and that the intensity of this phenomenon can be limited by using step carburizing, where carburizing stages applied during heating to the target temperature shorten the exposure time at the target temperature. Simultaneously, an increase in carbon concentration in the surface layer causes a limitation of Mn escape due to attractive interactions with carbon atoms. All the above aspects cause the kinetics of the carburizing process, and consequently the effect of heat treatment after carburizing, to depend on changes in the chemical composition of the surface layer. It has also been proven that the influence of manganese volatilization decreases with increasing carburized layer thickness, regardless of the process implementation method.