Impact of Temperature Variation on Friction Behaviour of Rare Earth-Doped Diamond-like Carbon Coatings with Ionic Liquid Lubricants

Abstract

This research paper investigates the tribological performance of diamond-like carbon (DLC) coatings doped with rare earth metals (europium and gadolinium) as well as pure DLC lubricated with ionic liquid additives (trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate {[P66614][DEHP]} and 1-ethyl-3-methylimidazolium diethyl phosphate {[EMIM][DEP]}) in Polyalphaolefin 8 (PAO8). The study aims to examine the effect of temperature on the interaction between the coatings and additives by conducting tribological experiments using a block-on-disk setup at temperatures of 60 °C, 80 °C, and 100 °C. The primary objective is to evaluate the performance of doped DLC coatings compared to pure DLC coatings with ionic liquid additives in the lubricant in boundary lubrication conditions at various high working temperature environments. The experiments reveal that doped DLC coatings with ionic liquid additives exhibit superior tribological performance compared to pure DLC coatings. The rare earth metal dopants play a positive role in the formation of a tribofilm on the surface of the coatings as it interacts with ionic liquids, resulting in a lower coefficient of friction (CoF). Temperature influences the performance of the coatings and additives. The CoF increases with temperature for pure DLC coatings, while for doped DLC coatings it was significantly less. These findings highlight the influence of temperature on the tribological behavior of DLC coatings. Overall, this study contributes valuable insights into the impact of rare earth metal dopants and ionic liquid additives on the tribological performance of DLC coatings under different temperature conditions. The results demonstrate the potential of utilizing doped DLC coatings with ionic liquid additives as an effective approach to enhance the performance of mechanical systems.

Influence of 1-Ethyl-3-methylimidazolium Diethylphosphate Ionic Liquid on the Performance of Eu- and Gd-Doped Diamond-like Carbon Coatings

“…This observation is supported by multiple research studies [17][18][19][20][21]. The incorporation of metallic or non-metallic elements as dopants offers a means to diminish residual stress by regulating the microscopic arrangement, adhesion, sp 3 /sp 2 ratio, and surface texture of DLC coatings. Consequently, the capacity to control the carbon bond structure and minimize residual stress emerges as a pivotal element for achieving the desired properties within a DLC film [19].…”

“…Various studies have established a correlation between the intensity of the D peak (I D ) and the intensity of the G peak (I G ) with the concentration of sp 3 , wherein a lower I D /I G value signifies a higher proportion of sp 3 in Table an increase in the dopant fraction resulted in a rise in the I D /I G ratio of pure DLC, escalating from 0.73 to 0.88 for Gd and to 0.80 for Eu. Although limited studies focus on incorporating lanthanides as dopants in DLC films, Foong et al [59] observed a similar trend in their research.…”

“…This, in turn, enables significant energy preservation throughout the lifespan of the system. Effective friction management further extends the durability of components by reducing undesirable deterioration, leading to favorable energy conservation outcomes through the diminished necessity for component replacements [1][2][3]. Therefore, currently, there is a huge emphasis on creating advanced materials that can effectively reduce friction and enhance the durability of mechanical components in motion.…”

Effects of Rare Earths on Microstructure and Wear Resistance in Metal Additive Manufacturing: A Review

“…In addition to enhancing metal coatings, REEs also enhance the tribological properties of carbon films (DLC [152] and GLC [153,154]) and bone-like apatite. The dense structure of the DLC film results in excellent friction and wear resistance.…”

Effect of Europium and Gadolinium Alloying Elements on the Tribological Response of Low Hydrogen Content Amorphous Carbon

“…While most published studies focused on doping and/or alloying a-C coatings with metals or metalloids, doping a-C films with rare-earth elements − and rare-earth oxides , has only recently been explored. As one example, Omiya et al, Sadeghi et al, and Shaikh et al evaluated the tribological properties of gadolinium (Gd)- and europium (Eu)-alloyed a-C films deposited by high power impulse magnetron sputtering (HiPIMS) in the presence of synthetic oil containing a class of promising additives for transmission fluids, namely phosphonium phosphate ionic liquids. , The results of tribological experiments and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) measurements indicated that only the introduction of Gd in the a-C matrix favors the formation of a transfer layer on the steel counterbody that enhances the generation and adhesion of a lubricious and antiwear boundary layer (i.e., tribofilm) from the lubricant additives . As another example, Meng et al investigated the effect of the introduction of lanthanum (La) in DLC films grown by magnetron sputtering on the resulting mechanical, tribological, and wetting properties .…”