Effect of the Synergetic Action on Tribological Characteristics of Ni-Based Composites Containing Multiple-Lubricants

Abstract

Ni-based self-lubricating composites with multiple-lubricants addition were prepared by a powder metallurgy technique, and the effect of multiple-lubricants on tribological properties was investigated from room temperature to 700 °C. The synergetic effects of graphite, MoS2, and metallic silver lubricants on the tribological characteristics of composites were analyzed. XRD analysis showed that new CrxSy and Mo2C phase were formed in the composites containing graphite, MoS2 and metallic Ag lubricants during the sintering process. The average friction coefficients (0.69–0.22) and wear rates (11.90–0.09 × 10−5 mm3 N−1 m−1) were obtained when rubbing against Inconel 718 alloy from room temperature to 700 °C due to synergetic lubricating action of multiple-lubricants. A smooth lubricating was gradually generated on the worn surface, and the improving of tribological properties was attributed to the formation of lubricious glaze film on the worn surface and their partially transferred to the counterface. The graphite played the main role of lubrication at room temperature, while molybdate phase and graphite were responsible for low friction coefficients and wear rates at mid/high temperatures. The synergetic lubricating effect of molybdate (produced in the rubbing process at high temperatures) iron oxide (transfer from disk material to the pin) and remaining graphite multiple-lubricants play an important lubricating role during friction tests at a wide temperature range.