Wear Of Diamond-like Carbon Films Research Articles

A Comparative Study on Impact Wear of Diamond-Like Carbon Films on H62 and GCr15 Steel

A Comparative Study on Impact Wear of Diamond-Like Carbon Films on H62 and GCr15 Steel

Superlow friction of amorphous diamond-like carbon films in humid ambient enabled by hexagonal boron nitride nanosheet wrapped carbon nanoparticles

The friction and wear of amorphous diamond-like carbon (DLC) films will dramatically increase with the increment of ambient humidity. This drawback can lead to lubrication failure, which greatly impedes the practical applications of DLC films in humid environment. Herein, a simple method is proposed to improve the tribological performance of DLC films in humid environment by adding hexagonal boron nitride nanosheet wrapped carbon nanoparticles (CNP@h-BNNSs) as lubricants. The reciprocating friction tests demonstrate that DLC films with CNP@h-BNNSs as lubricants possess excellent antifriction and antiwear performance at the relative humidity (RH) of 7.5–55%. Especially, it can achieve a superlow friction and wear at the RH of 45–55% which decrease by respectively 13 and 25 times as compared to those obtained from DLC films without lubricants. The investigation on the steel ball surface after friction test shows that a protective tribo-layer containing carbon, boron and nitrogen elements is formed. The existence of this tribo-layer can effectively reduce the friction and protect the steel ball surface from excessive wear. Noteworthy, the h-BNNSs are exposed at the friction interface acting as lubricating layer while the carbon nanoparticles are adsorbed on steel ball surface playing as binding binder. Furthermore, the ball movement mode of CNP@h-BNNSs and the interaction between water molecules and CNP@h-BNNSs are also considered as key factors to reduce friction. All these results indicate that CNP@h-BNNSs which can be massively produced have the potential to reduce the friction and wear of DLC films in humid environment.

Probing carbon-based composite coatings toward high vacuum lubrication application

Abstract For challenges in minimizing friction and wear of spatial mechanical systems, synergetic lubrication coatings were prepared by spinning liquid lubricants and hybrid greases on the diamond-like carbon (DLC) films, and were evaluated whether they could achieve a long-term safe and reliable operation under high vacuum. Under high vacuum conditions, liquid lubricants significantly reduce the friction and wear of DLC films. Hybrid greases not only show excellent lubrication performance, but also greatly enhance the tribological behavior of DLC films, especially the grease with optimal proportion. Such excellent tribological performance of DLC-based composite coatings at low applied loads depends on the synergy of DLC and fluid film, in reverse the tribo-chemical reaction film under harsh working conditions.

Friction and wear of diamond-like carbon film deposited on CoCrMo alloy under different lubrication

Abstract CoCrMo alloys are widely used as artificial joint implants due to their excellent mechanical properties, good wear resistance and outstanding corrosion resistance. However, the risks of release of cobalt and chromium ions urge researchers to improve the wear resistance of implants further by using surface modification technology. Diamond-like carbon film with 3.0 μm thickness was deposited on the surface of CoCrMo alloy using ion-source-assisted magnetron sputtering. The friction coefficients of the CoCrMo alloy decreased remarkably under different conditions after the formation of diamond-like carbon film. After the deposition of diamond-like carbon film the wear rates of the CoCrMo alloy decreased by 52.4 %, 47.1 % and 49.4 %, under dry friction, physiological saline, and bovine serum lubrication, respectively.

Friction and wear characteristics of hydrogenated diamond-like carbon films formed on the roughened stainless steel surface

The effects of the surface roughness of hydrogenated diamond-like carbon (DLC) films on friction and wear properties have been studied using a ball-on-disk type tribometer in air and water environments. Rough DLC films were formed by depositing DLC with the plasma-enhanced chemical vapor deposition method on roughened stainless steel substrate prepared by argon plasma sputter etching. DLC films deposited on a smooth stainless steel substrate showed unstable friction behavior in both air and water environments. The final friction coefficient values ranged from 0.10 to 0.15 in air and 0.15 to 0.20 in water. Line-shaped large-scale delamination of DLC film from stainless steel substrate was observed for smooth DLC films rubbed in water. In an air environment, large-scale delamination was not observed, but wear of the DLC film could be seen. The wear scar formed on the stainless steel ball under water lubrication was larger than that formed in air environment. In contrast to smooth DLC film, DLC films having a rough surface showed stable frictional behavior. The friction coefficients in water and air environments were approximately 0.1 and 0.2, respectively. No large-scale delamination of DLC film was observed for rough DLC films. Although friction characteristics were improved by roughing the surface of the DLC films, the wear scars forming on the ball surface became larger with increases in the surface roughness of the DLC film. From the results of the tribotest in n-decane, which has almost the same viscosity as water, it was suggested that not only the hydrodynamic effect but also the interaction between DLC films and water affect the friction and wear behavior. DLC films changed from hydrophobic to hydrophilic by tribochemical reaction in water environment. The low friction and wear of DLC films under water lubrication is considered to be caused by hydrophilication of the DLC films.

On the possible role of triboplasma in friction and wear of diamond-like carbon films in hydrogen-containing environments

Hydrogen-free diamond-like carbon (DLC) films (both amorphous (a-C) and tetrahedral amorphous carbon (ta-C)) suffer high friction and severe wear losses when tested in inert and/or high vacuum environments. However, they provide anomalous superlow friction and wear coefficients in the presence of hydrogen gas, water vapour and alcohol molecules in the test environment. In this paper, we used such films in a systematic study to further confirm that hydrogen indeed plays an important role in their friction and wear behaviours. To study the effect of hydrogen, we conducted sliding tests in a hydrogen-containing test chamber and analysed the chemistry of their sliding contact surfaces using a time-of-flight secondary ion mass spectrometer. Clearly, the sliding contact regions of the carbon films became very rich in hydrogen after tribological tests in the hydrogen-containing chamber. In an attempt to understand the fundamental tribochemical mechanisms involved, we performed additional tests on these DLC films using a highly instrumented tribometer that permitted us the visualization of triboplasmas generating at or in the vicinity of the sliding surfaces. In this test system, we confirmed the formation of a triboplasma inside the contact area of the DLC films as evidenced by the characteristic UV radiation. Based on these observations, we believe that the formation of such triboplasmas within the contact zones of these DLC films may have triggered unique tribochemical reactions between hydrogen and carbon atoms on their sliding surfaces and thus resulted in very low friction and wear during tests in hydrogen-containing environments.

305 Ti・ステンレス基材に対するSi中間層を用いたDLC膜の密着性の研究(ライフサポートにおける工学技術,オーガナイズドセッション)

In this paper, a-Si inner layer has been proposed to improve the adhesion of DLC (diamond-like carbon) films to SUS, Ti and TiNi substrate. The Si inner layer was coated on SUS316L, Ti and TiNi substrates using radio frequency (RF) magnetron sputtering, and then the DLC film was coated on the Si coated substrate using radio frequency plasma enhanced chemical deposition (CVD). To investigate the characteristic of the inner Si layer, XRD spectra and the contact angle of aqua distillate droplet were measured. The wear of DLC film was measured using ball-on disc test. The results showed the Si inner layer was effective to improve the adhesion of the DLC film.

Modeling the Tribochemical Aspects of Friction and Gradual Wear of Diamond-Like Carbon Films

Problems in nanomechanics often need to combine mechanical approaches together with methods of physics and chemistry that are outside of the traditional mechanics scope. Recent experimental studies of dry sliding between two hydrogenated DLC (diamond-like carbon) coated counterparts in low oxygen environment showed that adsorbates have considerable influence on friction and the friction coefficient increases with the increasing of the time interval between contacts. The observed friction phenomena are assumed caused by a reaction between the adsorbate and carbon atoms of the coatings, and when the slider passes a point on the track, it removes mechanically some adsorbate from the surface. The mechanical action leads to reexposure of the surface to gases in the environment. This paper focuses on physical and tribochemical processes that occur in sliding contact between the DLC coated slider and the counterpart. We develop further our recently presented model of the process and assume that there is a transient short-life high temperature field at the vicinities of contacting protuberances that may cause various transformations of the surface. In particular, the sp 3 phase of DLC films may transform to graphite-like sp 2 carbon. Our model does not depend directly on the assumption that the adsorbate is oxygen. However, due to the prevalence of oxygen in atmospheric gas it is assumed that the adsorbate is oxygen in the model presented. We suppose that first an oxygen molecule becomes physically adsorbed to the surface and then due to rubbing the molecule dissociates into two chemically active oxygen atoms. This process leads to chemisorbtion between the carbon atoms of the coating and the sticky oxygen atoms. The latter atoms can interact with the counterpart. Our modeling established a direct connection between this kind of molecular friction and gradual wear. In particular, it is shown that the initial roughness of the DLC surface may have a considerable influence on the probability of breaking bonds during mechanical removal of adsorbate. Ab initio calculations of the bond dissociation energies between carbon atoms and carbon-oxygen atoms were performed using GAUSSIAN98 at the Miller-Plesset level of model chemistry. The bond dissociation energy found for the carbon-carbon bonds is 523 kJ/mol, while for the carbon-oxygen bonds it is 1447 kJ/mol. It is assumed that carbon wear particles will not be formed during gradual degradation since the coating carbon molecules are dissolved within the environment gases. The model helps to explain how microscopic processes, such as the breaking and forming of interatomic bonds, may affect macroscopic phenomena, such as friction and wear.

Friction and wear of DLC films on magnesium alloy

Diamond-like carbon (DLC) films are well known for their high hardness, low friction and excellent wear resistance. Therefore, DLC film coating can contribute to improving mechanical and tribological properties of materials. DLC films have usually been deposited on super hard alloys. So far, few reports about DLC films deposited on soft materials have been published. In recent years, magnesium has been widely used because of its lightweight and ease of recycling. However, magnesium alloys are inferior in wear resistance and corrosion resistance. Therefore, it is necessary to improve these properties to use magnesium for more machine parts. DLC films were deposited on the magnesium alloy substrate by the plasma CVD method using radio frequency (RF). The friction and wear properties of the films were investigated under dry conditions, and in corrosive solutions of 3 mass% sodium chloride (NaCl), 0.05 normal hydrochloric acid (HCl) and 0.05 normal sodium hydroxide (NaOH) conditions. The process used to deposit the DLC coating was confirmed to be effective in decreasing the friction coefficient and improving the corrosion wear resistance in 3 mass% NaCl and 0.05 normal NaOH solutions. However, DLC films showed poor corrosion wear resistance in 0.05 normal HCl due to the existence of pits in the films.

高エネルギーイオンを用いて形成したダイヤモンドライクカーボン膜のマイクロトライボロジー特性

The effects of high energy ion-implantation treatment on the mechanical properties of diamond-like carbon (DLC) films have been investigated in this study. The micro-tribological properties of DLC films formed by using various methods such as ion-beam enhanced deposition (IBED) and plasma based ion-implantation (PBII) have been examined by means of atomic force microscopy (AFM) and acoustic emission (AE) oscillation scratch tester. With the PBII method DLC films were deposited on silicon wafer under conditions of a pulse bias of −5 to −20kV in an atmosphere of CH4 plasma. DLC films were deposited with the IBED Method by means of ion-plating and the deposition was performed using the methods of dynamic mixing and static mixing at an acceleration voltage of 120kV. These main results of above-mentioned tests are summarized as follows. (1) In case of DLC films deposited by the PBII method, there is an existing peak voltage at which the maximum hardness and durability were provided. (2) DLC films deposited with PBII method shows higher hardness than these deposited with the IBED method does but they also have brittleness is large. Therefore, the quantity of micro wear of DLC films with PBII was larger than that of DLC films with IBED. (3) The critical load of PBII-DLC films increased with an increase on a peak voltage. And, the adhesive strength of ion beam mixing DLC films deposited at 120kV is similar to that of PBII films deposited at a peak voltage of several tens of kV.

Friction and wear of DLC films on 304 austenitic stainless steel in corrosive solutions

Diamond-like carbon (DLC) films are well known for their high hardness, low friction and excellent wear resistance. In the present work, the friction coefficient and wear resistance of DLC films deposited on 304 austenitic stainless steel were investigated in corrosive solutions. DLC films were deposited on the substrate by the CVD method using radio frequency (13.56 MHz) plasma. A mixture of methane (CH 4) and hydrogen (H 2) was used as processing gas. The CH 4 concentration was varied from 20 to 100%. DLC films were subjected to friction and wear tests using a ball-on-flat surface friction apparatus in solutions of 3 mass% NaCl, 0.05 N HCl, 0.05 N H 2SO 4 and 0.05 N HNO 3. The flat surface was oscillated against the alumina ball. In the tests performed within the corrosive solution, the friction coefficients of the DLC films and substrate were approximately 0.1 and 0.5, respectively. The DLC films deposited on the 304 substrate showed a remarkably lower volume of wear than the substrate alone. Accordingly, the DLC coating process was confirmed to be effective in decreasing the friction coefficient and improving the corrosion wear resistance of 304 in 3 mass% NaCl and acidic solutions.

308 水素含有量の異なる DLC 膜の摩擦摩耗特性

DLC (Diamond-like carbon) films have attractive properties that make it a good candidate for a wide range of critical engineering applications. DLC films with different hydrogen contents were deposited using plasma CVD and ion beam deposition methods with different raw materials. The effect of humidity on friction of DLC films differed depending on hydrogen contents, sliding speed, and normal load. The wear of DLC films in dry air was larger than that in humid air. The features of wear surfaces of DLC films varied by changing sliding conditions.

フッ化炭素プラズマ処理シリコン含有ダイヤモンドライクカーボン膜の機械特性

Diamond like carbon (DLC) and silicon containing DLC (Si-DLC) films were deposited by EBEP (electron beam excited plasma)-CVD. The effects of CF4 plasma treatment and Si-inclusion on DLC film on surface energy, nanoindentation hardness and nanoscratching properties were investigated. DLC and Si-DLC films were surface modified by CF4 plasma treatment. CF4 plasma treatment decreases surface energy evaluated by the liquid drop method. Si-inclusion decreases the nanoindentation hardness. CF4 plasma treatment decreases nanoindentaion hardness of DLC film, however increases the hardness of 20% Si containing DLC film. Micro wear depth increases by Si-inclusion evaluated by nanoscratch test. CF4 plasma treatment increases the micro wear of DLC film, however decreases the micro wear of 20% silicon containing DLC film. Friction coefficients of both DLC and Si-DLC films were decreased by CF4 plasma treatment.

The effect of humidity on the tribological behavior of diamond-like carbon (DLC) film coated on WC-Co by physical vapor deposition method

DLC films have been coated by PVD on WC-Co substrate with and without Si interface. They have been tested under low (∼20%) and high (∼80%) humidity conditions by reciprocating friction and wear apparatus. For ascertaining the wear mechanism from the topographies of DLC films, optical and SEM images of wear tracks have been taken. Wear debris particles behave as an abrasive agent, depositing into the film and causing the start of failure. There are multiple wear mechanisms, such as fatigue, abrasion, etc., existing simultaneously in the wear of DLC film in both cases. Wear rate decreases as the total wear way increases. For the case of DLC coating without Si interface there is a good correlation between wear rate and friction coefficient. However, this harmony disappears for DLC/Si coating. A chemically activated process may be assumed as the controlling step in the micro crack propagation during the generation of a wear debris particle. The different tribological behaviors of the DLC coatings under different environmental conditions are explained.

206 Effect of hardness of mating materials on friction and wear of DLC films

DLC (diamond-like carbon) films are one of the best candidates as anti-wear coatings for high performance mechanical elements and electric devices that require tribological enhancement and chemical stability. Most of previous researches on DLC films were concerning with DLC film itself or its properties. However, tribological characteristics of DLC film should be affected by properties of mating materials. In this paper, four kinds of mating balls were prepared for tribological tests of DLC film. The mating balls were made with same material (stainless) but apply different annealing conditions. The effect of hardness of mating material on friction and wear of DLC films has been measured with precision friction tester. Testing results shows, the harder the mating materials, the lower the friction coefficient and wear rate among results of martensite balls. The reason of high friction coefficient in soft mating materials considers as widen the contact area during experiment. It can be proved by measuring wear profiles on DLC films and wear trace on mating balls.

The effects of oxygen and humidity on friction and wear of diamond-like carbon films

Diamond-like carbon (DLC) films were prepared on Si(100) wafers by plasma-assisted chemical vapor deposition at a pressure of 900 mTorr. Their wear rates and friction coefficients against a silicon nitride ball were measured in a pin-on-disk tribometer in argon and air with varying relative humidities. In 50% relative humidity, the measured wear rates of the ball and DLC were of the order of 10−8 mm3 N−1 m−1 and 10−7 mm3 N−1 m−1 respectively. In dry argon, dry air and 100% humid air, the wear rates of DLC were 10−9, 10−9 and 10−8 mm3 N−1 m−1, but that of the ball was below the detection limit. The measured friction coefficients were 0.06 in dry argon, 0.08 in 50% humid air and 0.09 in 100% humid argon, and around 0.2 in 50% humid argon, dry and 100% in humid air. In dry argon, the contact area of the ball was covered with material transferred from the DLC film during sliding; the low friction coefficient and wear rate measured in dry argon are attributed to this material. In dry and humid air, surface layers of DLC were oxidized by a tribochemical reaction forming a CO bond. They covered the contact area of both the DLC film and the ball. This film increased friction coefficients, but it acted as a protective coating when its thickness was sufficient to prevent direct contact of the DLC film against the ball in 100% humid air.