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

Abstract

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 30keV and doses of 1017 and 2×1017ionscm−2. Tribological tests were conducted against cylindrical 100Cr6 pin at 200N load and 180mms−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 2.1×10−7mm3/(mm2s) 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.