The effect of nitrogen on the coarsening rate of precipitate phases in iron-based alloys with chromium and vanadium: experimental and theoretical investigations

Abstract

A comparison of the coarsening of nitrogen-rich vanadium precipitates and the coarsening of carbon-rich vanadium precipitates is presented. The precipitate phases are studied experimentally, via fabrication of model alloys, and theoretically, via simulations utilizing the DICTRA software. The experimental investigations indicate that the nitrogen-rich precipitates exhibit a slower coarsening behaviour than the carbon-rich precipitates. Analysis using thermodynamic and kinetic modelling shows that this can be explained by the higher thermodynamic stability of the nitrogen-rich precipitate compared to the carbon-rich precipitate. The calculated coarsening rates are compared with the measured rates, and found to be in satisfactory agreement using reasonable values for the interfacial energies. The investigations are motivated by the fine precipitate size distribution of nitrides and carbonitrides characteristic for high nitrogen alloyed tool steels produced by means of powder metallurgy.