This study introduces a simple annealing procedure that leads to the formation of a self-replenishing solid lubricant film on bulk boron carbide (B4 C) and its coatings. The procedure uses short duration annealing at 800°C for 15 min. Subsequently, the specimens are cooled to room temperature and tested in a pin on disc machine. During annealing, B4 C reacts with oxygen in air and forms a glasslike boron oxide (B2 O3 ) layer on the exposed surface. Eventually, this layer reacts spontaneously with moisture in the surrounding air, thus forming a thin boric acid (H3 BO3 ) 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 B4 C surfaces.