Influence of carbon on the structural-phase composition and hardness of steel ingots of the Fe-Cr-Mo-N-C system obtained by the SHS method under nitrogen pressure

Abstract

The possibility of obtaining solid ingots (without gas porosity in the volume) from high-nitrogen steel of the Fe-Cr-Mo-N-C system by the method of self-propagating high-temperature synthesis under nitrogen pressure is shown in the present paper. It has been established that with an increase in the mass fraction of carbon from 0.09 % to 0.30 % in the as-cast metal, the hardness of the metal increases. At the same time, the structural-phase composition consists of a pseudo-pearlitic structure (ferrite-nitride mixture) and austenitic structure in different ratios since an increase in the carbon content leads to an increase in the amount of the pseudo-pearlite. The heat treatment of specimens with a mass fraction of carbon of 0.09 % and 0.30 % at 1250°C for two hours leads to their complete austenization. In this case, the hardness of steels of both compositions decreases to 22 – 24 HRC (0.09 wt.% of carbon) and to 28 – 30 HRC (0.30 wt.% of carbon).