Low energy implantation to inhibit wear in N+ ions implanted WC–Co composite

• We address the effects of low energy implantation of nitrogen on WC–Co composite.
• We perform tribological tests on four samples with different Co content.
• We analyze the material removal process and associated mechanisms i.e. amorphization.
• We pointed out the wear regime and damage mechanisms within the worn surface.

This work discusses the influence of nitrogen ion (N+) implantation on wear resistance of WC–Co composite. The WC–Co samples were bombarded at low N+ ions energies of 20 and 30 keV and doses of 1017 and 2 × 1017 ions cm−2. Tribological tests were conducted against cylindrical 100Cr6 pin at 200 N load and 180 mm s−1 speed. The tests use water lubrication and four sample types with Co binder content ranging in 6.5–25%. The X-ray spectra reveal that implantation is able to transform the original [CFC] Co structure of virgin surface to harder amorphous phase. However, it was found that excessive low binder content alters the wear behavior on non-implanted samples since it causes wear rate transition from 0.59 × 10−7 to 2.1 × 10−7 mm3/(mm2 s) imposing hence instable wear regime. The SEM micrographs confirm the formation of transferred film within the implanted worn surface owing to (i) an enhancement in Co flow and (ii) a generation of oxides (Fe2O3, Fe3O4, Co2O3, WO2). While the formed film acts to inhibit severe abrasion, the material removal process combining cobalt flow and carbide grains pull-out seems to be associated with oxidation mechanisms to be accentuated with energy increase. The most improvements in wear resistance were observed on samples with the highest Co content and the results were found more sensitive to N+ ions implantation energy than dose.