Tribological properties of MoN layer on silver-containing nickel-base alloy at high temperatures

Silver is a good lubricant at moderate temperature while oxides of molybdenum are effective at high temperature. In order to improve surface wear resistance and realize self-lubrication over a wide temperature range, molybdenizing and nitriding duplex-treatments were performed on the silver-containing nickel-base alloy by utilizing a double glow plasma alloying technology. The tribological properties of molybdenized and nitrided duplex-treated layer on silver-containing nickel-base alloy were tested on a ball-on-disk tribometer from room temperature to 600 °C against a counterface of Al2O3. The molybdenizing and nitriding (MoN) layer mainly consisted of MoN and Mo. The friction coefficient of MoN layer was 0.3–0.7 from room temperature to 600 °C. At room temperature, the friction coefficients and wear rates of nickel-base alloy were found to increase by duplex treatment because of the hindrance provided by the compound MoN layer to the diffusion of silver. However, the molybdenized layer was helpful for the friction and wear reduction at high temperature due to the formation of oxides of molybdenum.