In-situ array TiN reinforced Al-Cr-Ti-Nb-Mo refractory high-entropy alloy coating on Ti-6Al-4V alloy by gas assisted laser nitriding.

In this work, a novel lightweight AlCrTiNbMo refractory high-entropy alloy (RHEA) coating has been developed to overcome the surface damage defects in Ti-6Al-4V alloys under wear and erosion conditions. A crack-free in-situ nitride (AlCrTiNbMo)N x RHEA coating were successfully prepared by the gas assisted laser nitriding. According to XRD, SEM and TEM analysis, AlCrTiNbMo coating was composed of single BCC phase, while (AlCrTiNbMo)N x coating was constituted by BCC and TiN phases. The average microhardness of AlCrTiNbMo and (AlCrTiNbMo)N x RHEA coatings were 591.2 HV 0.3 and 1070.1 HV 0.3 respectively. (AlCrTiNbMo)N x RHEA coating has lower friction coefficient and wear rate than AlCrTiNbMo RHEA coating and the substrate from room temperature to 600 °C. At 600 °C, (AlCrTiNbMo)N x RHEA coating showed a rare self-lubricating behavior, the friction coefficient decreased to 0.275 (61.9 % of the substrate), and the wear rate was 0.06 mm3/N m× 10−4 (1.24 % of the substrate). The erosion rates of (AlCrTiNbMo)N x RHEA coating at erosion angle of 30°, 60° and 90° were 11.0 %, 22.3 %, and 36.8 % of those of the substrate, respectively. The homogeneous and hard TiN array-BCC structure generated by in-situ self-reaction was the main factor for the excellent wear and erosion resistance of (AlCrTiNbMo)N x RHEA coating. Thus, (AlCrTiNbMo)N x RHEA coating and corresponding laser nitride technique were expected to be applied in the severe working environment of high temperature, wear, and erosion. • In-situ nitride (AlCrTiNbMo)N x refractory high-entropy alloy coating by gas assisted laser nitriding was first proposed. • The wear and erosion performance of Ti-6Al-4V alloy was improved significantly and the effect mechanism was investigated. • The homogeneous and hard TiN array-BCC structure generated was the main factor for the excellent performance. [ABSTRACT FROM AUTHOR]