Improvement in the Wear Resistance under Dry Friction of Electrodeposited Fe-W Coatings through Heat Treatments

The influence of the microstructural transformations upon heat treatments on the wear resistance of Fe-W coatings is studied. The coatings are electrodeposited from a glycolate-citrate plating bath with 24 at.% of W, and the wear resistance is investigated under dry friction conditions using ball-on-disc sliding tests. The samples were annealed in Ar atmosphere at different temperatures up to 800 degrees C. The microstructural transformations were studied by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Electron Backscattered Diffraction (EBSD) technique. Except for the coating annealed at 800 degrees C, all the tested coatings suffered severe tribo-oxidation which resulted in the formation of deep cracks, i.e., 15 m in depth, within the wear track. The precipitation of the secondary phases, i.e., Fe2W and FeWO4, on the surface of the sample annealed at 800 degrees C increased the resistance to tribo-oxidation leading to wear tracks with an average depth of 3 m. Hence, the Fe-W coating annealed at 800 degrees C was characterized with a higher wear resistance resulting in a wear rate comparable to electrodeposited hard chromium coatings, i.e., 3 and 4 x 10(-6) mm(3)/N m, respectively.