In situ investigation of the gas–solid interaction between high-alloyed steel powder and nitrogen by energy dispersive diffraction

This study investigates the temperature-dependent gas–solid interaction between gaseous nitrogen and two different high-alloyed steel powders: CrMn austenitic steel X40MnCrN19-17, and vanadium-rich cold-work tool steel X245VCrMo9-4-4. A time- and temperature-resolved synchrotron study was performed to investigate the phase composition of the powder materials during continuous heating. In addition, the nitrogen uptake of each phase was investigated by measuring the lattice constant of the respective phase. Thermodynamic calculations of the phase composition and the amount of dissolved interstitials in the calculated phases were performed and compared to the experimental results. This study reveals that heating in gaseous nitrogen leads to nitrogen uptake into both steels, which influences the phase composition. The first gas–solid interaction starts at 700 °C. Depending on the chemical composition of the steel powder, nitrogen is measured to be dissolved in different phases. Thermodynamic calculations were used to predict the phases in which nitrogen is dissolved.