Application of the voltammetry of microparticles for characterizing wear debris produced in the sliding wear regimes of steels

Electrochemical characterization of wear metallic particles produced during pin-on-disc sliding tests is not conventionally carried out, possibly because of their small grain size, irregular shape and heterogeneous composition. The characterization of its reactivity can be important in the study of the relationship between oxidative and mechanical processes occurring at the sliding interfaces. Towards this goal, here we report the application of voltammetry of microparticles methodology to investigate the reactivity of sliding wear debris from steels. Low alloy (AISI 4140) and tool (AISI H13) steels were used as pin and disc materials, respectively, during the sliding wear tests. The variations of hardness of both sliding bodies resulted in the operation of mild and severe wear regimes. The worn surfaces were examined by stereoscopic and scanning electron microscopes. The wear particles were mechanically immobilized on the surface of a paraffin-impregnated graphite rod electrode and characterized by voltammetry in 0.1M HClO₄. The voltammograms reveal important information on oxidation stability of worn surfaces. Results were confirmed by electrochemical impedance spectroscopy measurements of both pin and disc surfaces for the mild and severe wear. (paper)