Self-Replenishing Solid Lubricant Films on Bulk Boron Carbide (B_4C) and Coatings

摘要

This study introduces a simple annealing procedure that leads to the formation of a self-replenishing solid lubricant film on bulk boron carbide (B_4C) and its coatings. The procedure uses a short-duration annealing at 800 deg C for 15 min. Subsequently, the samples are cooled to room temperature and tested in a pin-on-disk machine. During annealing, B_4C reacts with oxygen in air and forms a glasslike boron oxide (B_2O_3) layer on the exposed surface. Eventually, this layer reacts spontaneously with moisture in the surrounding air, thus forming a thin boric acid (H_3BO_3) film. The friction coefficients of 440C steel and zirconia pins against this film are 0.04-0.06. Electron microscopy and Raman spectroscopy were used to elucidate the formation and self-lubricating mechanisms of this solid-boundary film on sliding B_4C surfaces.