Application of non-metallic mineral materials as additives in lubricating oil

In recent years, the study of inorganic silicate natural minerals as new lubricant anti-friction and anti-wear additives has received extensive attention at home and abroad, and has gradually become a research hotspot in the field of tribology.

Studies have shown that silicate mineral powders with a layer (chain) structure such as serpentine, talc, montmorillonite, and attapulgite can form a friction reaction film on the surface of the friction pair, which can effectively repair the worn surface. Microscopic damage and enhance its mechanical properties, significantly reduce friction, reduce wear, improve the operating conditions of railway locomotive internal combustion engines, heavy-duty vehicle engines and other equipment under harsh conditions such as high speed and heavy load, showing good application prospects.

Jin et al. found that serpentine as a lubricant additive can form a self-healing reaction film composed of metal oxides and hard ceramic phases on the surface of iron-based friction pairs, reducing the friction factor of base oil and metal wear volume by more than 20% , the friction surface hardness is more than 1 times higher than that of the base oil lubricated lower surface.

Rudenko investigated the tribological properties of talc powder as lubricant additives at different temperatures, and found that talc formed a dense friction reaction film on the surface of the metal friction pair at 100 °C, which significantly reduced friction and wear. Studies by Yu Xiang et al. show that talc powder and its high-temperature calcination products can significantly reduce the surface roughness of the friction pair, thereby greatly reducing the frictional resistance.

Cao et al. also confirmed that silicate minerals such as montmorillonite, kaolin, and muscovite can significantly improve the lubrication of iron-based friction materials as anti-wear and anti-friction additives. and Fe-based reaction film.

Nan et al. evaluated the tribological behavior of surface-modified attapulgite fibers as lubricant additives through the test results of a reciprocating sliding wear tester. The addition of mineral powder reduced the friction coefficient of 150SN base oil by 50%. The wear volume of carbon steel is reduced by 30%, and a friction reaction film composed of various oxides is formed on the wear surface; at the same time, it is found that nano-Ni powder and attapulgite fibers have a good synergistic effect, which can promote the friction between attapulgite and Fe-based Tribochemical reaction between pairs, so that the friction factor and wear volume are further reduced by more than 30% on the original basis.

As a silicate mineral with a layered chain transition structure, sepiolite is very similar in structure to serpentine, attapulgite and other minerals, and has the structural conditions and performance advantages as a lubricant additive. Yin Yanli et al. compared the friction-reducing and lubricating properties of surface-modified sepiolite, attapulgite and serpentine as lubricant additives, and found that the tribological properties of sepiolite were similar to those of the same fibrous The structures of attapulgite minerals are comparable, and both are better than the serpentine powders that are widely studied and used at present, which is related to the higher content of oxides and graphite in the friction reaction film formed.

Huang Haipeng et al. used a pin/disk sliding wear tester to investigate the tribological properties of untreated sepiolite powder with an average particle size of 7.5 μm as an additive for 150SN base oil. Reduce friction and reduce wear. However, due to the lack of surface modification and refinement of the powder, it was found by ferrography analysis that a large amount of iron-based abrasive debris was distributed on the surface of the oil sample containing sepiolite, and there were obvious large-sized sepiolite agglomerates. Its anti-friction lubricating properties are unfavorable.

Yin Yanli et al. used the wet chemical modification process to modify and refine the surface of the raw sepiolite mineral powder, and obtained nano-scale sepiolite short fibers with good dispersion stability in lubricating oil. The modified sepiolite powder as 500SN lubricating oil additive showed good anti-friction and anti-wear properties under different load and frequency conditions. Under the load of 100N and the frequency of 20Hz, adding 0.5% (mass fraction) of sepiolite can reduce the friction coefficient of lubricating oil and the wear volume of the lower sample by 69.5% and 71.7%, respectively. Sepiolite particles form a friction surface film composed of iron oxides, oxide ceramics, graphite and organic compounds on the friction surface of 45# steel. The friction surface film has good mechanical properties, which can significantly reduce friction and reduce wear.