Experimental Study on Wear Behavior of Polyacetal Nanocomposite Gears

Hypothesis: 

The effect of incorporation of carbon black nanoparticles (CB) and nano-precipitated calcium carbonate (NPCC) on wear behavior, thermal behavior and morphology in polyacetal (POM)-based nanocomposite gears has been studied. Polyacetal is one of the widely used engineering materials for manufacturing the gears. Nevertheless, heat resistance and relatively low crack impact strength and sensitivity to UV are the major disadvantage of POM. Adding carbon black nanoparticles into the polyacetal can simultaneously increase the tensile strength and toughness and increase the UV resistance of the polyacetal. In addition, the presence of NPCC in the POM/CB can lead to improvements in CB dispersibility, increase of wear and thermal resistance.

POM/CB/NPCC nanocomposite gears containing 0.42% (by wt) carbon black and different fractions (1.5%, 3% and 4.5% all by wts) of NPCC were produced by utilizing a twin-screw extruder and injection molding machine. Morphology and nanostructure were investigated by applying scanning electron microscopy. The gear performance of nanocomposites was examined by applying a gear test rig. Gear tests were performed in the mode constant loading. The temperature and wear of the gears were evaluated in the gear tests. 

The simultaneous addition of both types of nanoparticles to polyacetal led to a reduction in the amount of wear by 58% compared to pure polyacetal. The temperature of the gear surface, in the same number of revolutions, was reduced using CB and NPCC nanoparticles. The decrease in the temperature of the nanocomposite tooth surface compared to pure POM was attributed to the increase in storage modulus and improvement in elastic behavior, decrease in damping ratio, as well as decrease in friction coefficient and increase in heat transfer in presence of nanoparticles. The use of 4.5% (by wt) of NPCC nanoparticles caused cracks and expansion of wear and material flow in the gear pitch zone.