Mechanism and Observation of Pore Formation during Carbonitriding

Abstract Carbonitriding enhances properties of many steels and is therefore an attractive alternative for surface hardening of steel components in the mechanical industry. However, pore formation in the carbon and nitrogen enriched surface layer may occur under certain process conditions. For a given steel and case depth specification, pore formation can be managed by reducing the nitrogen activity of the carbonitriding atmosphere below a defined limit, depending on process temperature and process time. Recent progress in process control allows automatic and independent adjustments of the carbon and nitrogen activities and corresponding potentials of the carbonitriding atmosphere. This study contributes to the practical evaluation of pore formation limits under selected carbonitriding conditions for a range of commonly used engineering steel grades.