A simple strategy for fabrication of an FCC-based complex concentrated alloy coating with hierarchical nanoprecipitates and enhanced mechanical properties

Highlights: • A simple and effective strategy was proposed for fabrication of complex concentrated alloy coatings. • The complex concentrated alloy coating exhibits dense microstructures and good metallurgical bonding with substrate. • A high density of hierarchical intragranular nanoprecipitates was contained in clad layer. • Microhardness of clad layer is higher than those of most reported face-centred cubic-based high-entropy alloys. -- Abstract: An increasing number of recent studies have indicated that the best balance of mechanical properties of a high-entropy alloy (HEA) needed to meet the requirements of practical structural applications require to produce second precipitates in an HEA matrix. This type of alloy is more appropriately classified as a complex concentrated alloy (CCA) rather than an HEA. Here, we report a simple strategy for the fabrication of CCA coatings with high mechanical properties. In this strategy, the face-centred cubic (FCC)-based Co₂₅Cr₂₅Cu_12.5Ni₂₅Al_12.5 (at.%) system was chosen, and spark plasma sintering was first used to prepare the Co₂₅Cr₂₅Cu_12.5Ni₂₅Al_12.5 CCA clad layer directly on a Q235 substrate from simple mixed powders. Our results show that the CCA coating was fabricated successfully on the substrate and that the clad layer exhibited a dense microstructure, a low dilution ratio and good metallurgical bonding with the substrate. A high density of hierarchical intragranular nanoprecipitates was contained in the clad layer. Precipitation strengthening, as one of the main strengthening mechanisms, contributes to a microhardness value of 455 HV for the clad layer, which is much higher than those of most reported FCC-structured HEAs, even some BCC-structured refractory HEAs and several BCC-based HEAs with high Al contents.