Microstructure, microhardness and high-temperature tribological properties of CoCrFeNiMnTi0.3 high entropy alloy coating manufactured by powder-bed arc additive manufacturing

In this study, a high entropy alloy (HEA) coating of CoCrFeNiMnTi0.3 with good mechanical and tribological properties has been successfully manufactured on a mild carbon steel by the powder-bed arc additive manufacturing (PBAAM) technique. The HEA coating is consisted of a face-centred cubic (FCC) solid solution phase together with a small amount of in-situ formed fine TiN and TiO2 precipitates. The HEA coating has quite uniform chemical composition, microstructure, as well as hardness. The average Vickers microhardness is about 185.6 ± 3.1 HV0.1 in the HEA coating and 148.9 ± 3.4 HV0.1 in the mild carbon steel substrate. Besides, in comparison with the substrate, the PBAAM manufactured CoCrFeNiMnTi0.3 HEA coating always shows a lower friction coefficient and smaller specific wear rate for a given wear testing temperature from RT to 800 °C. Particularly, the friction coefficient and specific wear rate of the HEA coating is only about 71.63 % and 3.68 %, respectively, of that of the mild carbon steel substrate. It can be concluded from the findings in this work that cladding a protective CoCrFeNiMnTi0.3 HEA coating on the mild carbon steel by PBAAM technique is beneficial into reducing both friction and wear, and thus is an effective strategy to significantly improve the application potential of mild carbon steel at high temperatures.