Corrosion Behavior of High Entropy Alloys Made By Directed Energy Deposition Additive Manufacturing

Abstract

Additive manufacturing (AM) is an attractive process for fabricating high entropy alloys (HEAs) with the ability to leverage high cooling rates for the single phase formation of complex alloys. This study investigates the corrosion behavior of the equi-atomic CoCrFeMnNi HEA made by directed energy deposition in the as-built and homogenized condition (1100oC for 1 hr). The as-built microstructure exhibited dendritic chemical segregation with interdendrite areas enriched with Mn and Ni compared to the chemically uniform microstructure after annealing. Corrosion behavior of the CoCrFeMnNi HEAs was investigated using potentiodynamic polarization measurements in 0.6 M NaCl solutions to determine each materials open circuit and breakdown potential, on average -0.25 VSCE and ~0.40VSCE, respectively for both conditions. Comparison in pit propagation was also explored with the as-built microstructure showing preferential corrosion of the Mn/Ni enriched interdendrite areas while the annealed materials pits were similar to those observed on 304L stainless steel. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.