Tribological Performance of Sub-Micron Scale Boric Acid Powder Additives for Extended Duration

In this investigation, the friction and wear performance of sub-micron scale boric acid powder lubricant additives were studied during extended duration pin-on-disk experiments. The sub-micron (600 nm) and micro (4 μm) powder additives were created from 250 micron sized crystals using an 1800D SPEX Mill/Mixer. Lubricant combinations were prepared by homogeneously mixing the additives with canola oil in a vortex generator. Three different boric acid additives were investigated by combining 5.0 wt. % of 4 μm boric acid particles, 5.0 wt % of 600 nm sized boric acid particles, and a 5.0 wt % mixture of the 4 μm (2.5 wt. %) and 600 nm (2.5 wt. %) boric acid particles. A fourth additive, 5.0 wt. % of 0.5 – 5μm MoS₂ powder, was also purchased and mixed with the canola oil to form a basis for comparison. It was determined that the oil mixed with a combination of micro and sub-micron scale boric acid powder additives exhibited better frictional performance than the oil mixed with micro or sub-micron boric acid additives.