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Abstract. Experiments have been carried out to investigate the effect of carburization process on the sliding wear resistance of mild steel. The carburization process was conducted in carbonate salts mixtures of Na2CO3-NaCl. Carburization followed by water quenching resulted in the formation of martensite with a hardness of 900 HV in the subsurface, up to the depth of 400 µm. This hardness value was substantially higher than the non-carburized steel which had a hardness of 520 HV. In the initial stage of sliding in air, abrasive wear and cluster of fine cavities due to adhesion were formed. This was followed by the formation of large-scale fracture at the cavities. The high hardness of the carburized steel reduced the severity of adhesive wear and thus the tendency of the worn surface to fracture.

The tribological behaviour of carburized steel with different microstructures, produced by varying the carburization time was investigated. Increasing the carburization time from 1 h to 3 h resulted in higher hardness and greater martensite content, which had a stronger tendency to form a better anti-wear oxide. In turn, these improved properties enhanced the adhesive wear resistance and delayed the occurrence of fracture. Longer carburization also resulted in the formation of expanded martensite and shallower grain boundaries with fewer precipitates, which further enhanced the fracture resistance of the steel. Larger scale fracture occurring on steel carburized for 1 h resulted in cracked WC grains, the formation of more undermined WC grains and cavities (due to the removal of WC grains) and severe grooving on the cemented carbide counterbody. In conclusion, this carburization process was effective in enhancing the wear resistance of mild steel which subsequently reduced the wear of the cemented carbide counterbody.