Long-term surface restoration effect introduced by advanced silicate based lubricant additive

Long-term effect (up to 300 h) of an advanced silicate based lubricant additive on the tribological properties is studied using a newly designed pin-on-disk tester. With the additive, the coefficient of friction was reduced by ∼40%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) examinations showed that a smooth and high C-content outer layer was formed on the specimen surfaces, suggesting possible formation of diamond-like carbon (DLC) films. Using nano-hardness measurements, the hardness of the layer on the disk and the pin were 10.2 GPa and 16.7 GPa respectively. Wear loss and ferrographic analyses indicated that a “negative wear” occurred when the additive was applied, suggesting the debris particles were captured by the specimen to form a self-repairing layer.