In order to extend the permissible operating temperature up to 1000 °C, ceramic materials may be the sole and serious candidates for controlling friction and wear, and requiring corrosion/oxidation resistance. Advanced structural ceramics have high hardness between 15 GPa and 30 GPa at room temperature and such high hardness is maintained up to high temperature. Hence, advanced structural ceramics are expected to be suitable for tribo-systems at elevated temperatures. However, the high hardness and low adhesive junction of ceramics does not exhibit beneficial effect for high wear resistance and low friction coefficient at elevated temperatures. It is a result of the low toughness leading to microfracture at contact surfaces during sliding process, which reduces wear resistance and increases plowing effect. A major challenge in advanced structural ceramics is to develop long-lifetime and reproducible tribo-components for use in mechanical systems that involve high loads, velocities and temperatures. A feasible solution is to develop ceramic matrix high temperature solid-lubricating composites, which have gained extensive attentions among academics in recent years. Yttrium-stabilized tetragonal zirconia polycrystalline ceramic reveals high fracture strength, which responds through a phase transformation mechanism of tetragonal to monoclinic symmetry. Consequently, zirconia ceramic is a potential candidate matrix for high temperature solid-lubricating composite. The match of solid lubricants (e.g., graphite, MoS2, BaF2, CaF2, Ag, Ag2O, Cu2O, CuO, BaCrO4, BaSO4, SrSO4 and CaSiO3) for zirconia ceramic are investigated intensively to evaluate their potentials as effective solid lubricants at a broad temperature range. It was found that CuO provides ZrO2 with low friction coefficient of 0.18–0.3 from 700 °C to 1000 °C,additionally, SrSO4 added ZrO2 offers low friction coefficient of below 0.2 and wear rates in the order of 10−6 mm3/Nm under very low sliding speed from room temperature to 800 °C. The studies on the composite solid lubricants display the distinct tribological behavior at a wide temperature range. The combination of graphite and CaF2 reveals that graphite can provide low-temperature lubrication but it is feeble to improve tribological behavior of ZrO2 ceramic at 400 °C and 600 °C. As for ZrO2eAgeCaF2 composite, a little content of Ag cannot provide lubrication for ZrO2 ceramic at low temperatures, while ZrO2 matrix composite containing large content of 35 wt% Ag can render a relatively low friction coefficient of about 0.4 from room temperature to 800 °C. With respect to the combination of MoS2 and CaF2, ZrO2eMoS2eCaF2 composite can offer satisfactory microhardness (HV 824 ± 90) and fracture toughness (6.5 ± 1.4 MPam1/2), and exhibit favorable friction coefficient of 0.25–0.40 from room temperature to 1000 °C owing to the synergistic action of MoS2, CaF2 and CaMoO4 formed on the worn surface by tribo-chemical reaction. Furthermore, the effect of tribo-pair on friction and wear properties of ZrO2eMoS2eCaF2 composite shows that ZrO2 matrix composite has a low friction coefficient in entire temperature range when sliding against Al2O3 ceramic, exhibiting high friction coefficient at moderate temperature when coupled with SiC and Si3N4 ceramics. The reason is that the hard SiOx particles generated from oxidation of SiC and Si3N4 ceramics destroy the lubricating CaF2 film on the worn surface at 600 °C.
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