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. (C) 2003 Elsevier Science B.V. All rights reserved.