Mechanical properties and microstructural characteristics of sinter-hardened steels

Purpose: The main goal of this paper was the examination of the role of W addition on properties of two sinterhardened alloys with two different carbon levels. Additionally the influence of sinter-hardening process has been evaluated. Microstructural characteristic and mechanical properties of Ni-Mo steels with increasing amount of tungsten (from 0 to 0.3% wt.) were taken under consideration. Design/methodology/approach: Powder mixes have been compacted at 700MPa and sintered in a vacuum furnace with argon backfilling at 1120°C for 60 minutes. Rapid cooling has been applied with an average cooling rate of 2.5°C/s. Obtained steels were analyzed by scanning microscopy with energy dispersive spectroscopy (EDS) for phase distribution and mapping and light optical microscopy for observations of the microstructure. Charpy impact test, three-point bending, microhardness, pin-on-disk and disk-on-disk tests were used. Findings: The outcome of implemented vacuum sintering with rapid cooling as well as chemical composition were studied in terms of mechanical properties, focusing in particular on impact energy, hardness and wear resistance. The results achieved after the investigation of Ni-Mo and Ni-Mo-W sinter-hardened steels with low and high carbon content proved that applied process of sintering under vacuum and rapid cooling brought expected outcome. Research limitations/implications: The characteristics of powders and the applied cooling rate were found be a good compromise for mechanical properties and microstructures, though further researches should be carried out in order to examine different cooling rates and parameters of tempering process. Originality/value: The effect of W and/or WC additions to highly alloyed steels is well known. In the work the effect of small additions of W and WC to low alloyed steels, especially in terms of hardenability and wear resistance, was investigated.