Tribochemical effects on the friction and wear behaviors of diamond-like carbon film under high relative humidity condition

Abstract

Friction and wear behaviors of diamond-like carbon (DLC) film in humid N 2 (RH-100%) sliding against different counterpart ball (Si 3 N 4 ball, Al 2 O 3 ball and steel ball) were investigated. It was found that the friction and wear behaviors of DLC film were dependent on the friction-induced tribochemical interactions in the presence of the DLC film, water molecules and counterpart balls. When sliding against Si 3 N 4 ball, a tribochemical film that mainly consisted of silica gel was formed on the worn surface due to the oxidation and hydrolysis of the Si 3 N 4 ball, and resulted in the lowest friction coefficient and wear rate of the DLC film. The degradation of the DLC film catalyzed by Al 2 O 3 ball caused the highest wear rate of DLC film when sliding against Al 2 O 3 ball, while the tribochemical reactions between DLC film and steel ball led to the highest friction coefficient when sliding against steel ball.

The friction of diamond-like carbon coatings in a water environment

“…The presence of hydrophilic groups plays an important role in the low friction in a water environment. The presence of Fe-C bonding was shown on the DLC wear track [52,57], as well as Fe-O, C-O, C=O, and O-C=O bonding, relating to tribochemical reactions of the DLC coating with steel, and with the environment. These reactions control the coefficient of friction, and not the hydrogen content on the DLC coating.…”

“…Additionally, Li et al [51,52] investigated the tribochemistry of hydrogenated DLC coatings tested in a 100% RH nitrogen environment against a range of counterface materials. Against a steel ball, the coefficient of friction increased gradually from 0.05 to 0.2 over the duration of the test.…”

“…For DLC coatings sliding against steel in humid conditions, Li et al [51,52] proposed the following reaction mechanism (Fig. 6); mechanical cracking to the DLC surface occurs during sliding as a result of shear forces, breaking C-C and C-H bonds and producing macro-radicals which may react with the environment.…”

“…These reactions control the coefficient of friction, and not the hydrogen content on the DLC coating. Reaction mechanisms for the oxidation of a DLC coating in a humid environment, and the reaction of Fe with a DLC coating in a humid environment, have been suggested [51,52].…”

Friction Characteristics of DLC and WC/C

“…However, previous studies mainly focused on the effects of materials and coating conditions of solid lubricating films [4][5][6][7][8], materials and physical properties of mating Journal of the KSTLE surfaces [9,10] and environmental conditions [11][12][13][14][15] on the friction characteristics of solid lubricating films. The studies on the effects of sliding velocity and normal load [16,17] were not enough.…”