Contact stress induced wear mechanism transitions of PcBN/Al2O3 under vacuum and air conditions


 Since the millennium, incremental breakthroughs in aerospace have attracted widespread attention from countries around the world on deep space exploration. Technological innovations in ceramic and superhard materials have also played a key role in deep space exploration. Inspired by this, a tribological ball-disk experiment of polycrystalline cubic boron nitride (PcBN) sliding against aluminum oxide (Al2O3) was implemented in air and vacuum conditions, in order to evaluate the friction and wear properties of PcBN based on drilling in deep space environment. The results prove that the coefficient of friction (CoF) is interrelated with load and wear conditions, where CoFs gradually decrease with load growth in both air and vacuum. When the loads keep increasing, however, the wear mechanisms finally change under the high Hertz contact stress and lead to the CoF lift. Detailed characterizations were made to verify the tribological behaviors of the microscopic surface and chemical composition. Lastly, by analyzing the surface topographies and chemical residues, it is certain that the wear mechanisms change due to the high Hertz contact stress. As a result, abrasive wear and adhesive wear turn to furrow wear in air and three-body wear in vacuum. These results can influence actual work in deep space by reducing large stress loads to avoid the impact of severe vibrations on precision instruments during work and improving cutting removal efficiency by selecting the appropriate loading.