Electrochemical response of heterogeneous microstructure of laser directed energy deposited CoCrMo in physiological medium

The present work investigated the electrochemical properties of laser-based additively manufactured CoCrMo in simulated body fluid, at physiological temperature (37 ^∘ C). The extremely rapid thermokinetics inherently associated with the laser-based additive manufacturing led to heterogeneous microstructural evolution with cellular dendritic solidification and selective elemental segregation in CoCrMo fabricated using five different laser parameters. Such heterogeneous microstructure and composition led to spatially non-uniform corrosion response in additively manufactured CoCrMo. Despite such unique heterogeneity, the potentiodynamic polarization and electrochemical impedance spectroscopic parameters of the additively manufactured samples varied marginally compared to those of a conventionally manufactured CoCrMo sample. The heat treatment in argon at 1150 ^∘ C for 150 min followed by furnace cooling led to a spatially uniform corrosion pattern with enhanced equilibrium potential in additively fabricated CoCrMo. Such improved corrosion response of additively fabricated CoCrMo samples was attributed to the formation of coarser equiaxed grains with discontinuous precipitation of Cr and Mo rich compounds/carbides at the boundaries and the absence of high-energy ϵ -martensite phase.