Recent advances in the study of refractory high-entropy alloys (RHEAs) have increased the interest in understanding the high-temperature properties of compositionally complex alloys (CCAs). Considering the higher susceptibility of RHEAs to oxidation, this study focuses on investigating the creep properties of equimolar noble metal CCAs under high-temperature conditions. In contrast to other metallic high-temperature materials like Nickel-based superalloys or the recently studied RHEAs, noble metal CCAs are much less susceptible to oxidation and corrosion at elevated temperatures.

The tested CCAs consist of selected ternary and quaternary equimolar compositions that form a single-phase solid solution at temperatures of 1000°C and above, with each alloy containing three or four elements from gold (Au), iridium (Ir), palladium (Pd), platinum (Pt), and rhodium (Rh). The formation of a single-phase solid solution was predicted with Thermo-Calc, using the TCNOBL3 database.

The mechanical stability of these alloys at high temperatures was investigated via indentation creep testing at 1000°C, 1200°C and 1400°C using an Al2O3 flat punch indenter. Reaction tests indicated no chemical interaction between the indenter material and the noble metal CCAs, reaffirming their potential to be used at high temperature and in corrosive environments.

In-depth analysis of equimolar configurations on the alloys' behaviour under creep conditions provided significant insights, thereby enriching the understanding of solid solution strengthening in noble metal CCAs at temperatures of up to 1400°C.