Enhanced Performance of Automotive and Industry Precision Components by Advanced Carbonitriding Technology

Due to their enhanced mechanical properties, gas carbonitrided steel components containing martensite and nitrogen stabilized austenite are currently widely used for highly loaded and severe application conditions. Carbon and nitrogen (C–N) concentration profiles developed during the gas carbonitriding have significant effect on the final properties of the steel. To achieve consistent properties and increase the reliability of processes, simulation of the C–N profile and evolving precipitates during the carbonitriding is essential. Generally, it is observed that the surface nitrogen content developed in the low-alloyed bearing-grade steels is much higher compared to the nitrogen potential in the furnace atmosphere during gas carbonitriding. The formation of nitrides/carbonitrides is one of main reasons for this difference. Thus, diffusion equations cannot be directly applied to calculate the C–N profile, as they do not include precipitation. To solve this problem, a mathematical approach is developed in this work. Thermodynamic data from MatCalc and experimental data are used to formulate equations to calculate the precipitated fraction of C–N during carbonitriding. Furthermore, these equations are integrated with diffusion equations to predict C–N profile that includes precipitates and the developed model is validated with experiments.