Or0404—Effect of a Tribochemical Reacted Film on Friction and Wear Properties of DLC Coatings

Abstract

Diamond‐like carbon (DLC) coatings provide low friction properties without lubricants and, with lubricants, should provide super low friction. In this study, the friction and wear properties of DLC coatings with lubrication in the sliding contact area were evaluated to find an environmentally friendly material combination that can provide super low friction (i.e., a coefficient of friction lower than 0.01). The friction and wear properties of a steel pin on a DLC coated disk with lubrication were evaluated by using environmentally friendly fluids (organic acid or alcohol) as lubricants. In a sliding test of tetrahedral amorphous carbon (ta‐C) lubricated with DL (a mixture of dextrorotatory and levorotatory molecules)‐lactic acid, a super low coefficient of friction (0.01) was obtained at the end of the test and was much lower than that of an uncoated disk and an amorphous hydrogenated carbon (a‐C:H) disk. The coefficient of friction obtained with DL‐lactic acid was lower than that seen for acetic acid or glycerol. The ta‐C disk lubricated with DL‐lactic acid showed a small wear scar width. The main reason for the reduced friction and wear is probably attributable to the formation of a tribochemical reacted film in a tribochemical reaction with the acid. An oxidation film (white colored layer) of FeO also formed on the mating pin under DL‐lactic acid lubrication in the sliding contact area. These results showed not only the difference in the adsorbed lubricants due to the chemical structure of DLC, but also that the oxidized condition of the steel pin influenced the coefficient of friction.

The Influence of DLC Coating on EHL Friction Coefficient

“…Several other authors have also studied the interaction between DLC coatings and the combination of ZDDP and MoDTC [2,1,17,10,12]. However depending on lubricant composition, additive package and type of DLC coating both friction and wear performance varies greatly so it is hard to draw any general conclusions [24,27,22,13].…”

Tight-binding quantum chemical molecular dynamics simulations of the low friction mechanism of fluorine-terminated diamond-like carbon films

“…Diamond-like carbon (DLC) is one of the most promising solid lubricants because it shows excellent tribological properties in ultrahigh vacuum (UHV), such as ultralow friction, high chemical resistance, and high wear resistance. [1][2][3][4][5][6][7][8][9][10][11][12] As a result, DLC lms are used in thermal engine parts in cars, 13 bearings, 14 and optical storage disks, 15 as well as for biomedical applications. 16 Recently, some elements, such as hydrogen, silicon, nitrogen, and uorine, have been added to DLC to improve the tribological properties.…”

Low Friction Property of Diamond-Like Carbon Coating Films and Oxygen Transmission Ratio of Amorphous Carbon Films Deposited by Advanced Coating Processes

“…This ultra-low friction is thought to be generated by forming very thin and weak tribofilm at the mixed lubrication condition. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Martin et al proposed the possible mechanism of the super low friction was the forming water layer by the tribochemical reaction between ta-C and glycerol. [28][29][30][31][32][33] In this paper, the formation of water and acid was indicated as one possible chemical reaction for glycerol, as shown in (a) (a) (b) (b) For the oleic acid test, the water can be supplied from the ambient air.…”