Effects of water environment on tribological properties of DLC rubbed against brass

Abstract

The effects of the water environment, such as temperature, dissolved ions, dissolved oxygen etc., on the tribological properties of diamond-like carbon (DLC) against brass were studied as part of the development of water-lubricated hydraulics, valves and cylinders based on metals (Fe alloys, Cu alloys etc.). A ball-on-disk type tribotester was used to examine the above various factors. DLC was deposited on stainless steel disks using an unbalanced magnetron sputtering system. Pure water and quasi-tap water, which imitates typical tap water sampled in Tokyo, were used to study the effects of dissolved ions. The water temperature was elevated from 20°C to 80°C. The results show that temperature as well as the dissolved ions have a major impact on friction and wear. More specifically, the coefficient of friction was increased at elevated temperatures. Also, in pure water, abrasive wear of DLC was observed due to aluminum condensation on the brass surface, whereas it was prevented in quasi-tap water since aluminum was removed from the contact region due to the dissolved ions. EPMA, XPS and AES indicated Page 2 of 28 A c c e p t e d M a n u s c r i p t that the tribo-layer on the metal surfaces, which consists of carbon and the base metal as well as some elements from water, plays an important role.

Progress in Tribological Properties of Nano-Composite Hard Coatings under Water Lubrication

“…On the other hand, Uchidate et al [48] found that the accumulation of alumina on brass aggravated the wear of DLC:H coatings in pure water, while the ions in tap-water slowed down the accumulation rate of alumina on brass. Therefore, the wear rate of DLC:H coatings in tap-water was lower than that of DLC:H coatings in pure water even at different temperatures (see Figure 3b).…”

“…In addition, Uchidate et al [48][49][50] also found that the high temperature inhibited the formation of a whole lubricating film in water, which led to a high friction coefficient and wear rate. temperature inhibited the formation of a whole lubricating film in water, which led to a high friction coefficient and wear rate.…”

Study of the Industrial Application of Diamond-Like Carbon Coatings Deposited on Advanced Tool Steels

“…Additionally, the high stress induced by ion bombardment during deposition and the large mechanical property mismatch between the coating and the substrate contribute to the poor adhesion demonstrated by Ashtijoo et al [27]. Furthermore, the wear and friction properties of DLC coatings under boundary lubrication conditions have been investigated by Uchidate et al [28], indicating that the wear of steel and friction is strongly affected by the hardness and surface roughness of the DLC. These factors collectively contribute to the negative impact of nitriding on the adhesion between tool steel and DLC coatings.…”

Nano-Indentation Measurement of the Tribo-Layer on Stainless Steel and Brass Surfaces Rubbed against DLC in Water

“…It has also shown that the tribo-layer is very important for the diamond-like carbon (DLC) coated surfaces 6,7) , which is the topic of great interest in the industry today. Researchers have studied tribology of the DLC rubbed against stainless steel and brass in the water and results have shown that the friction and wear are strongly affected by the tribo-layer formed on the metal counter surfaces, which varies depending on the dissolved ions and the water temperature 8,9) . It was assumed that the tribo-layer has a gel-like structure and prohibits the direct contact between the DLC and metal if it is formed properly.…”