Preparation And Performance Research Of Ni-based Self-lubricating Composites

With the development of aviation, aerospace and military industry, friction, wear and lubrication problem at high temperatures is getting more and more attentions. It's urgent to develop solid lubricating materials with good mechanical and tribological properties at wide temperature range (room temperature-800℃). In this paper, the Ni-Al-based, Ni-Cr-based self-lubricating composites were prepared by powder metallurgy (PM) method, and the effects of contents of graphite and molybdenum disulfide (MoS₂) on mechanical and tribological properties of Ni-Cr-based composites were investigated, meanwhile, the influences of sintering temperature, test load and frequency on mechanical and tribological properties were also studied.The results show: for the Ni-Al based composites, with the increase of the sintering temperature, the compactness and micro-hardness increase, and the tribological properties become more stable. During the tribological test, with the rise of the load and the decrease of the frequency, the friction coefficient reduces. Furthermore, addition of 5 wt. % flake graphite to Ni-Al-based self-lubricating composites results in the obvious decrease of the micro-hardness and the friction coefficients at ambient temperature and 600℃.For the Ni-Cr-based composites containing graphite and MoS₂, with the rise of MoS₂, the micro-hardness of composites degrades significantly, while the friction coefficient and wear rate of the composites do not change evidently as the content of MoS₂ increasing from 10 wt.% to 15 wt.%. With the rise of graphite content, the micro-hardness of composites reduces gradually, and the friction coefficient increases slightly at 400℃and 800℃. When the content of graphite is 10 wt.%, the friction coefficient of composite was lowest at room temperature. Addition of 5% MoS₂ and 10% graphite, the friction coefficient of composites keeps 0.48-0.65, meaning the synergic lubricating effect between graphite and MoS₂, but the wear rate is an order of magnitude higher than the composites containing MoS₂ alone or graphite alone.For the Ni20Cr-graphite composites, with the rise of graphite, the compactness and micro-hardness gradually reduce, and the friction coefficient and wear rate of composites gradually decrease at room temperature and 400℃, while those increase firstly, then decrease at 800℃. Adding 10 wt.% tungsten (W) into Ni20Cr-graphite composites, the micro-hardness raises. For the Ni20Cr-10W-graphite composites, with the increase of graphite, the friction coefficients lower in the entire temperature range, while the wear rate raises at room temperature, and increase firstly then decrease at 400℃and 800℃.