Nano-TiC reinforced [Cr–Fe4Co4Ni4]Cr3 high-entropy-alloy composite coating fabricated by laser cladding

The agitator blade made by 904 L stainless steel was subjected to serious corrosion-wear due to its low hardness in phosphoric acid reactors. In this aspect, various nano-TiC reinforced [Cr–Fe4Co4Ni4]Cr3 HEA composite coatings were designed using the cluster-plus-glue-atom model and fabricated on 904 L stainless steel by laser cladding. The phase structure of the composite coatings was composed of FCC solid solution and TiC phase. The microstructure observation detected that tiny TiC particles widely distributed along the inter-dendrites of FCC matrix. Also, the particle dimensions and volumes rapidly enhanced with the addition of TiC. Whereas, excessive TiC contents (≥12.5vol%) led to the generation of microcracks. The TEM results further confirmed that TiC particles did not decompose during laser cladding. With the addition of TiC, the microhardness, wear and corrosion resistance of the composite coatings gradually increased. Especially, the microhardness of [Cr–Fe4Co4Ni4]Cr3-15vol%TiC composite coating reached the peak value of 357.4 HV0.2, approximately twice higher than that of the substrate. It's specific wear rate (3.974 mm3 N−1 m−1) was lower than that of the substrate (5.545 mm3 N−1 m−1). Compared with 904 L stainless steel, the corrosion current density of [Cr–Fe4Co4Ni4]Cr3-15vol%TiC composite coating reduced by nearly an order of magnitude, the impedance increased by 3.5 times