Electrodeposited nanocrystalline cobalt-alloy coatings provide a method, via grain-refinement (3nm to 100nm avg. grain size) and Hall-Petch strengthening, to produce hard coatings that meet or exceed the hardness and wear performance of current (hard) chromium plating technologies. In addition to the more environmentally benign chemistry, nanocrystalline cobalt-alloy coatings also offer the potential to significantly outperform current hard chrome technology with respect to: (1) higher current efficiency, with reduced and/or eliminated risk of hydrogen embrittlement of the substrate, and possible removal of 'baking' procedures, (2) faster deposition rates, and (3) greater ductility, with absence of porosity and microcracking. In this paper, the synthesis, structure and properties of various electrodeposited nanocrystalline cobalt-alloys are reviewed. In particular, the mechanical properties (tensile, micro-hardness, wear, etc.) of these alloys will be presented and, where possible, compared with those of hard chrome.
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