In this study, nanographite (NG), as a lubricant additive, and polyimide (PI) were used to fabricate NG/PI composites via a hot compression molding process. The tribological properties of the NG/PI composites with different NG mass contents (0-10 wt%) were tested using a reciprocating ball-on-disc contact tribometer matched with a GCr15 rubbing pair. The thermal stability, surface hardness, and compression strength of the composites were discussed. The results revealed that a small quantity of nanofillers greatly reduced the friction coefficient and increased the wear resistance of the NG/PI composites. Despite a minor decrease in mechanical performance, the composite with 5 wt% of NG filler exhibited improved tribological properties; it showed a 55.63% reduction in the friction coefficient and a reduction of 97.39% in the wear rate compared with neat PI. Moreover, an increase in the glass transition temperature (T g ) of the NG/PI composites indicated the enhancement of their thermal stability and wear resistance. Scanning electron microscopy (SEM) analyses showed that the main wear mechanism of the composites was fatigue wear. These findings suggest that the 5 wt% NG/PI composite could be a significant contribution to the field of tribological engineering plastics.
The hydraulic support column bears loading and makes reciprocating motion ceaselessly for extended periods, so its service life is far shorter than that of the overall hydraulic support. This paper offers a comparative study on the surface coating of hydraulic support columns with hard chrome plating and high-velocity oxygen fuel (HVOF) thermal spraying refabricating to analyze the impact of different refabricating processes on the microstructure, hardness, corrosion resistance, and wear resistance of the coating (plating). The result shows that the structure of the HVOF coating is uniformly compact, and the HVOF WC10Co4Cr coating has better wear resistance, more than four times that of hard chrome plating. In the neutral salt spray test, the HVOF Ni60 coating shows rustiness at 720 h of the test, which suggests its corrosion resistance is nearly five times that of hard chrome plating. Hence, under the harsh corrosive wear environment, the refabricating HVOF Ni60 is a more suitable replacement for the hydraulic support column coating than the hard chrome plating. Thus, the HVOF Ni60 coating could be an effective replacement for hard chrome plating.
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