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

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 Co25Cr25Cu12.5Ni25Al12.5 (at.%) system was chosen, and spark plasma sintering was first used to prepare the Co25Cr25Cu12.5Ni25Al12.5 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. Keywords: Complex concentrated alloy coating, Spark plasma sintering, Hierarchical nanoprecipitates, Precipitation strengthening, Mechanical properties