Sliding wear behaviour of electrodeposited cobalt–tungsten and cobalt–tungsten–iron alloys

Hard-chrome plate is traditionally employed as a wear resistant surface. However, concerns that the processing of such materials is not environmentally friendly have lead to a search for potential replacements. This work examines the behaviour of two alloy systems, namely Co–W and Co–W–Fe. Alloys from these systems were electrodeposited onto steel substrates. The Co–W alloys were further heat treated to increase their hardness, although this was deemed unnecessary for the Co–W–Fe alloys which had high as-deposited hardnesses. The sliding wear behaviour of these materials was examined, along with the behaviour of a hard chrome under similar conditions. It was found that under some conditions, the Co–W alloys exhibited a wear resistance and a coefficient of friction similar to that of hard chrome. Moreover, the corrosion resistance of the Co–W alloys was higher than that of the hard-chrome plate. The Co–W–Fe alloys exhibited a high as-deposited hardness. At a critical iron level of 30 wt.%, the wear rate of these coatings decreased substantially. All the Co–W–Fe coatings were more corrosion resistant than the hard chrome; however, even the most wear resistant exhibited a high coefficient of friction and more wear than the hard chrome.