Corrosion resistant and tough multi-principal element Cr-Co-Ni alloys

Cr-Co-Ni Multi-Principal Element Alloys (MPEAs) with good combinations of strength and ductility were studied to determine their attendant corrosion performance. Three alloys - Cr45Co27.5Ni27.5, Cr33.3Co33.3 Ni-33.3, and Cr25Co37.5Ni37.5 - were produced in recrystallized and cold-worked states, and their electrochemical response was tested in a simulated seawater electrolyte. Increasing the Cr content improved the yield strength (sigma y) and ultimate tensile strength (UTS), while maintaining high (> 40%) uniform elongation. Potentiodynamic polarization and electrochemical impedance spectroscopy revealed high corrosion resistance of the alloys in simulated seawater, in particular the Cr-rich alloy (Cr45Co27.5Ni27.5). Furthermore, following 40% cold work, the Cr45Co27.5Ni27.5 alloy displayed a further improvement in corrosion resistance. The Cr45Co27.5Ni27.5 alloy displays mechanical and corrosion properties that exceed those of conventional structural alloys such as Ni-superalloys, stainless steels and most 3d-transition metal MPEAs, including those without appreciable ductility. Therefore, in the present work it is shown that increasing the Cr content in Cr-Co-Ni alloys leads to a better combination of mechanical properties and corrosion resistance in saline environment, as observed especially for the Cr45Co27.5Ni27.5 alloy. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that increasing the Cr content can improve the mechanical properties and corrosion resistance of Cr-Co-Ni alloys, especially in a simulated seawater environment, where the Cr-rich alloy performed exceptionally well.