Tribological Properties of Adaptive Ni-Based Composites with Addition of Lubricious Ag2MoO4 at Elevated Temperatures

Abstract

The Ni-based self-lubricating composites with addition of 10 and 20 wt% Ag2MoO4 were fabricated by powder metallurgy technique, and the effect of Ag2MoO4 on tribological properties was investigated from room temperature to 700 °C. The tribo-chemical reaction films formed on rubbing surface and their effects on the tribological properties of composites at different temperatures were addressed according to the surface characterization by SEM and Micro-Raman. The results show that the Ag2MoO4 decomposed into Ag and Mo during the high-temperature fabrication process. The friction coefficient and wear rate of the composites decrease with the increasing of temperature and Ag2MoO4 contents and the composites with addition of 20 wt% Ag2MoO4 exhibits the lowest friction coefficient (0.26) and wear rate (1.02 × 10−5 mm3 N−1 m−1) at 700 °C. The composition of the tribo-layers on the worn surfaces of the composites is varied at different temperatures. It is proposed that the improving of tribological properties of the composites at high temperatures are attributed to the synergistic lubricating effect of silver molybdate (reproduced in the rubbing process at high temperatures) and Fe oxide (transfer from disk material to the pin) formed on the worn surface.