Effects of hexagonal boron nitride and sintering temperature on mechanical and tribological properties of SS316L/h-BN composites

In this work, hexagonal boron nitride (h-BN)-embedded 316L stainless steel (SS316L/h-BN) composites were prepared using a conventional powder metallurgy process. In order to produce self-lubricating composites, various amounts of h-BN (10, 15 and 20 vol%) were incorporated. Effects of h-BN content and sintering temperature on the mechanical and tribological properties were of primary interest. The results suggested that an increase in h-BN content reduced the hardness of the composites, but that the hardness could be improved by increasing the sintering temperature. Addition of h-BN up to 20 vol% improved the friction coefficient of the composites. At a sintering temperature of 1250 °C, h-BN transformed into a boride liquid phase, which formed a eutectic during cooling and exhibited a deterioration effect on lubricating film formation of the h-BN, resulting in an increase in the friction coefficient of the composites. The specific wear rate was greatly reduced when the composites were sintered at 1200 °C. The lowest friction coefficient and specific wear rate in the composites could be found under the experimental conditions used in this work when using 20 vol% of h-BN at a sintering temperature of 1200 °C.

► 20 vol% h-BN in stainless steel gave the lowest friction coefficient.
► Sintering temperature of 1200 °C was recommended for optimum friction coefficient.
► h-BN in stainless steel transformed to a boride liquid phase at 1250 °C.