Clarify the role of Nb alloying on passive film and corrosion behavior of CoCrFeMnNi high entropy alloy fabricated by laser powder bed fusion

Effect of Nb alloying on passive film and corrosion behavior of laser powder bed fused CoCrFeMnNi high entropy alloy (HEA) was studied by microstructure analysis, electrochemical analysis and X-ray photoelectron spectroscopy. Nb alloying refined the grain size, promoted the Laves phase precipitation, and changed the inclusion type of the HEA. The improved corrosion resistance evidenced by increased pitting potential and polarization resistance was achieved by Nb alloying. Nb addition decreased the donor and acceptor density of the passive film, and altered its composition. The relationship of "microstructure-passive film-corrosion property" is discussed to illustrate corrosion enhancement mechanism of Nb alloying.