Scaling effects between micro- and macro-tribology for a Ti–MoS2 coating

How far does contamination help dry lubrication efficiency?

“…Several studies on such MoS 2 þTi coatings showed that their friction behaviours under air and dry N 2 are extremely good [20,22,23,30,31]. Such a coating has been recommended for use in vacuum [16], though one study concluded against it [22].…”

“…It appears that no one has yet precisely explained the mechanisms involved in those friction behaviours, either good or bad [16,32]. However, recent studies on MoS 2 þTi coating behaviour under air at different humidity levels [31,33] showed that, provided that the Ti content is lower than 20%, a high humidity level leads to higher friction and more debris than at low humidity level. Simmonds [20] also reported that high wear occurred in the early stages of MoS 2 þ Ti friction under air 50% HR.…”

“…Simmonds [20] also reported that high wear occurred in the early stages of MoS 2 þ Ti friction under air 50% HR. Lubrication appears, provided that a transfer film is formed on the counter body and is comprised of Mo, S, and Ti [31,33].The transfer film appears more stable at low humidity and accommodation appears to be mainly done by interfacial sliding and transfer film shearing [31]. The instability is attributed to a possible surface chemical reaction with the surrounding environment leading to instable and less adherent wear debris.…”

Comparison of the Effects of Surface Roughness of Wrought Aluminium Alloys on the Surface of Steel

“…When steady-state conditions are reached, the coefficient of friction is lower when roughness (Ra) is low by friction between the surfaces, so the correlation between roughness parameters and tribological behaviour is strong. However average roughness is the dominant on tribological behaviour properties of contact surfaces, under dry conditions [13] . Figure 4 shows the hardness vs. roughness (Ra) for A 6092, A5056 and A 3003 alloys under dry sliding conditions.…”

“…As a result, microtopography, contact between two moving surfaces is an important basis for the development of basic concepts [13] . Many studies have been conducted mainly in the lubricant friction morphology Al alloys with the effect of friction and wear resistance of these alloys.…”