Effect of Chromium and Molybdenum Increment on the Crystal Structure, Nanoindentation, and Corrosion Properties of Cobalt-Based Alloys
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This study investigates the influence of chromium and molybdenum content (Cr: 20?35?wt%; Mo: 5 and 10?wt%) in a cobalt?chromium?molybdenum alloy system on the phases present in the microstructure, the nanomechanical, and electrochemical behavior of the alloys. A linear increase in the hardness is found in relation to the increasing chromium content for both 5 and 10?wt% Mo contents, whereas reduced modulus demonstrates an inflection at 30?wt% Cr, which is influenced by the molybdenum content. The open-circuit potential, polarization resistivity, and linear sweep voltammetry disclose that passivity of Co?Cr?Mo alloys improves in line with increasing Cr until 30?wt%, with any further increase causing a depreciation in the corrosion properties. X-Ray diffraction and optical metallographic analysis confirm that as the chromium content transitions through the 25?30?wt% range, the sigma (?) phase begins to develop within the combined matrix of hexagonal close pack martensite (?) and face-centered cubic austenite (?) phase.