Effect of alloying ratios and Cu-addition on corrosion behaviour of CoCrFeNiMo high-entropy alloys in superheated steam containing CO2, H2S and HCl

This article reports the morphology and corrosion study of CoCrNiFeMo and CoCrNiFeMoCu high-entropy alloys (HEA) tested in a simulated superheated geothermal environment to evaluate whether the alloys are candidate materials for a corrosive high-temperature geothermal environment. The HEA alloys with different alloying ratios were tested in superheated steam at 350 °C and 10 bar gauge containing HCl, H2S, and CO2 with acidic condensate (pH = 3). The Cu containing CoCrNiFeMoCu alloys were prone to corrosion damage and corrosion rate was accelerated by intermetallic Cu rich sites but the CoCrNiFeMo alloys were not prone to corrosion in the test environment.