Tribological Properties of B4C Ceramics Prepared by Pressureless Sintering and Annealed at Different Temperatures

B4C ceramics were fabricated by pressureless sintering, and the tribological behaviors of B4C ceramics without and with a postannealing treatment at different temperatures were investigated. It was found that the pores of B4C ceramics prepared by pressureless sintering might cause large fluctuations in the coefficient of friction but did not increase the coefficient of friction. A B2O3 layer was not formed on the B4C ceramics after annealing at 700 °C, whereas an H3BO3 layer was formed on the B4C ceramics after annealing at 1000 and 1200 °C, respectively. B4C ceramics obtained a favorable self-lubricating property after annealing at 1000 or 1200 °C because of the formation of an H3BO3 layer during the annealing treatment. B4C ceramics annealed at 1200 °C exhibited the best self-lubricating properties, with the lowest coefficient of friction of approximately 0.08. The friction and wear mechanisms of B4C ceramics without and with a postannealing treatment are discussed in detail.