Wear behavior of sintered hexagonal boron nitride under atmosphere and water vapor ambiences

Hexagonal boron nitride was pressed and sintered at 2000 °C with CaB2O4 as an additive to promote its crystallization, which was used as an abradable sealing coating for aircraft turbo engines. Microstructures, phase compositions and tribological properties of the sintered hBN were tested, and the results show that CaB2O4 can effectively promote crystal growth of hBN at 2000 °C for 5 h in N2 ambience. The friction coefficients of the sintered hBN under atmosphere ambience increase as the temperature increasing from room temperature to 400 °C, and then decrease with further increasing of temperature up to 800 °C. Under water vapor ambience, friction coefficients of the sintered hBN are much lower than those under atmosphere ambience, which are attributed to a lamella-slip of hBN and the solid lubrication effect of H3BO3.

► CaB2O4 can effectively promote the crystallization of hBN at 2000 °C for 5 h under N2 ambience. ► The water vapor is benefit to the decrease of friction coefficients of the hBN. ► Lower friction coefficients of the hBN under water vapor ambience due to a lamella-slip and H3BO3.