Effect of different lubricants on microstructural and tribological properties of TC21 titanium alloy against Si3N4 under fretting-reciprocating sliding

The tribological properties of a Si3N4 ball sliding against a TC21 disc lubricated by pentaerythritol ester (5750), bis (2-ethylhexyl) sebacate (1088), 1-butyl-3-methylimidazolium tetrafluoroborate (L-B104) and an as-synthesized ionic liquid L-C8F17SO3P4444(L-4P) have been studied by an Optimol SRV-V oscillating reciprocating friction and wear with load, temperature and frequency. Scanning electron microscopy and X-ray photoelectron spectroscopy results showed that L-4P has an excellent extreme pressure wear resistant effect (750N) and the lowest friction coefficient (<0.08), in addition to possess excellent tribological behavior due to the formation of chemical reaction (SnF2 and a friction oxidation product lubrication film) and deposition films on the rubbing surface. The wear mechanisms were mainly adhesive wear, abrasive wear and microcosmic fatigue wear, with less cracks on the worn surface. Under the 5750, 1088 and L-B104 lubrications conditions, the friction coefficients were markedly increased with the load increasing and the values were larger, friction surface was a clear plowing effect. The wear mechanisms were mainly surface plowing and abrasive wear. In this investigation, the results demonstrated that L-4P could react with the TC21 titanium alloy to produce lubrication film to improve the tribological properties.