Tribological properties of silicon nitride ceramics modified by ion implantation

Surface modification by ion implantation has been carried out in order to improve the tribological properties of gas-pressure sintered silicon nitride ceramics. B+, N+, Si+ or Ti+ ions were implanted into the silicon nitride ceramics with a fluence of 2×1017 ions/cm2 at an energy of 200 keV. To evaluate the tribological properties of Si3N4, Block-on-Ring wear tests were conducted without lubricant, using the ion implanted Si3N4 as block specimens and commercially supplied Si3N4 as ring specimens. The specific wear rate of the ion-implanted Si3N4 could be drastically reduced to a value of 1.6×10−9 mm2/N, accompanied by a decrease in the friction coefficient in the initial stage. According to surface analyses it was considered that the high wear resistance and low friction coefficient are attributed to the amorphization and the increase of surface hardness of the ion implanted layer.