Dilatometric study of low-alloy steels with silicon carbide addition

Low-alloy steels produced via the traditional powder metallurgy process, using a die compaction, are currently widely used. Therefore, improving their properties is an issue that attracts much attention. The most common method of enhancing the properties of a given material is introducing additives, e.g., silicon to prealloyed low-alloy steels. It may be added through the mechanical alloying process. The article presents the results of research focused on an analysis of the influence of: (1) the mechanical alloying process, (2) various amounts of silicon carbide: 1, 2 or 3 mass% and carbon addition: 0.4 or 0.6 mass%, (3) different atmospheres, reducing or inert with 10 mass% of hydrogen and (4) the effect of annealing on phenomena occurring during the sintering of low-alloy steel. Moreover, changes in the sinters’ microstructure and microhardness were also investigated. Based on the results, it was found that an increase in the amount of silicon in the material causes an increase in the shrinkage of the samples, prepared using mechanical alloying, during the sintering process. This observed effect was independent of the carbon content (0.4 or 0.6 mass%) in the samples as well as of the sintering atmosphere (reducing or inert with 10 mass% of hydrogen). The smallest porosity was observed for samples sintered directly after the mechanical alloying process. There is no need to use a hydrogen atmosphere during sintering—10 % of hydrogen added to an inert, e.g., helium atmosphere is enough to sinter the samples correctly.