Tribological behaviour of smooth diamond films (original) (raw)
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Tribological properties of smooth polycrystalline diamond films
Diamond and Related Materials, 1995
We have used a pin-on-disk txibometer with either a monocrystalline ruby or a lOOCr6 steel ball to evaluate the tribological properties of a series of polycrystalline chemical vapour deposition diamond films. Different polishing treatments of the as-grown films resulted in marked differences of their tribological behaviour.
Tribological properties of polished diamond films
Journal of Applied Physics, 1993
Despite the rapid progress being made in the synthesis of diamond films and recent interest in polishing of diamond films, no systematic measurements of friction and wear on polished diamond films have been reported. In the present study, chemomechanical and laser polishing techniques are used, and friction and wear data on the chemomechanically polished diamond films are presented. With the chemomechanical polishing technique used in this study, the rms roughness of hot Filament chemical vapor deposited diamond films can be reduced from about 657 to about 170 nm with rounding off of sharp asperities with no change in the diamond structure. The polished films exhibit coefficient of friction ( -0.1) and wear rates much lower than that of unpolished films. Friction and wear properties of the polished films are comparable to that of single-crystal natural diamond. Based on this study, it is concluded that polished films are potential candidates for tribological applications. 4174
Tribological properties of smooth diamond films
Applied Surface Science, 1996
The friction and wear properties of smooth diamond coatings sliding against a monocrystalline ruby ball were studied using a pin-on-disk tribometer. The smooth diamond film surface was prepared either by (i) deposition of ultrathin nanocrystalline films in the thickness range from 0.2 to 2 /zm or by (ii) postgrowth polishing. Excimer laser surface ablation, microwave plasma etching and mechanical lapping with diamond grit were used for postgrowth polishing. A correlation of film surface properties examined with different techniques (atomic force microscopy, Auger electron spectroscopy, Raman spectroscopy, stylus profilometry) and the tribological properties of the diamond films tested was established. The influence of laser-induced surface graphitization on the friction coefficient of laser-polished films was investigated.
Investigation of the Tribological Properties of Diamond Films
Journal of Materials Engineering and Performance, 2007
A chemical vapor deposition (CVD) system has been used to produce polycrystalline and nanocrystalline diamond (NCD) films. For biomedical and electronic engineering applications, it is highly desirable to deposit smooth films with decreased crystal size. In general, diamond coatings with a crystal size of 10-100 nm range are known as NCD. There are several ways in which NCD may be deposited
Enhanced tribological performances of nanocrystalline diamond film
International Journal of Refractory Metals and Hard Materials, 2010
Diamond films are well known for their outstanding properties such as high hardness, possible low coefficient of friction, high thermal conductivity, excellent biocompatibility and electrical insulation. Diamond films with nanocrystalline grains (grain sizes between 3 and 15 nm) offer further advantages of low compressive stress, low surface roughness, and high amount of surface atoms in relation to volume leading to enhanced surface properties. In view of these, the present investigation is undertaken to explore the possibility of using nanocrystalline diamond (NCD) films in advanced automotive equipment. Accordingly NCD-films have been deposited using a modified hot-filament technique. Tribological behaviour of these films has been evaluated by means of a reciprocating model tribometer with different lubricant qualities. The worn surfaces were examined using scanning electron microscopy (SEM) and 3D white light confocal microscopy. The results show the influences of coating qualities and test conditions on the tribological response. Comparable friction coefficient can be found with high treated and low treated lubricants. These films exhibited negligible wear for the range of load tested.
Applied Surface Science, 2018
Polycrystalline diamond films with systematic change in microstructure that varies from microcrystalline to nanocrystalline structure are synthesized on Si by hot filament chemical vapor deposition. The morphology and structural properties of the grown diamond films are analyzed using field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray diffraction and Raman spectroscopy. The average roughness and grain size of the diamond films decrease with increase in CH4 to H2 ratio from 0.5 to 3 %. Also, structural disorder in these diamond films increases with decrease in grain size as evidenced from Raman spectroscopy. The coefficient of friction (CoF) is found to be very low for all the films. However, the average CoF is found to increase from 0.011±0.005 to 0.03±0.015 as the grain size decrease from ~ 1 m down to ~20 nm. Post analysis of wear track by FESEM, AFM based nanoscale friction and Raman spectroscopy reveal that microcrystalline diamond undergoes shear induced amorphization with negligible wear rate while nanocrystalline diamond films undergo shear induced plastic deformation without amorphization. A comprehensive mechanism for the observed CoF is discussed in the framework of microstructure, structural disorder and shear induced tribo-chemical reactions at the sliding interface.
Tribological properties of partly polished diamond coatings
Diamond and Related Materials, 2005
Extremely low friction coefficient was achieved with ''partly polished diamond coatings''. Diamond coatings were deposited onto Si substrates by MWCVD with the mixture of CH 4 and H 2. Deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy and Electron Spectroscopy for Chemical Analysis (ESCA). Sharp peak derived from polycrystalline diamond was observed by XRD. Whereas Raman profile of partly polished diamond coatings was close to that of ta-C. This result suggests that small diamond grains were surrounded by amorphous carbon structure in the diamond coatings. Deposited diamond coating was polished with each other. Surface roughness R a was reduced to 0.3, 0.2 and 0.08 Am, respectively. The hardness of the polished diamond coatings investigated by Nanoindentation technique was approximately 40.8 GPa, which was relatively lower value compared with conventional as-deposited CVD diamond coatings. For the tribological properties, we examined the effect of surface roughness using flat-ended pin-on-disk apparatus and ball-on-disk apparatus with bearing ball (SUJ2) and stainless steel (SUS304). Diamond coatings were deposited onto flat-ended pin and disk, and they were polished to R a = 0.3, 0.2 and 0.08 Am. After the 6000 cycle process extremely low friction coefficient, l = 0.05, was achieved with the pair of R a (flat-ended pin, disk) = R a (0.08, 0.3) in flat-ended pin-on-disk apparatus. In order to clarify the effect of surface roughness, ball-on-disk was carried out with different surface roughness, R a = 1.7, 0.3, 0.2 and 0.08 Am. Here as-deposited diamond coating, R a = 1.7 Am, was used as a reference point. Friction coefficient of l = 0.09 was obtained for both balls. After the tribological tests balls were analyzed by scanning electron microscope (SEM) and energy dispersed X-ray spectrometer (EDX).
AIP Advances, 2012
The dependence of the structural and morphological properties of nanocrystalline diamond films grown by hot filament chemical vapor deposition on the substrate temperature was studied. Friction coefficients of these films were measured and found to vary from high to ultra low, depending on the chemical nature of the films i.e., sp 2 and sp 3 phase fractions. For all films, the friction coefficient was found to decrease with increase in sp 2 /sp 3 phase fraction. The wear rate follows the trend of the friction coefficient and was likewise found to depend on the structural and morphological properties of the films. For all the films, the friction coefficient is found to decrease with normal load which is ascribed to sliding induced surface amorphization/graphitization.
Tribological properties of nanocrystalline diamond films
Surface & Coatings Technology, 1999
In this paper, we present the friction and wear properties of nanocrystalline diamond (NCD) films grown in Ar-fullerene (C 60 ) and Ar-CH 4 microwave plasmas. Specifically, we will address the fundamental tribological issues posed by these films during sliding against Si 3 N 4 counterfaces in ambient air and inert gases. Grain sizes of the films grown by the new method are very small (10-30 nm) and are much smoother (20-40 nm, root mean square) than those of films grown by the conventional H 2 -CH 4 microwave-assisted chemical vapor deposition process. Transmission electron microscopy ( TEM ) revealed that the grain boundaries of these films are very sharp and free of nondiamond phases. The microcrystalline diamond films grown by most conventional methods consist of large grains and a rough surface finish, which can cause severe abrasion during sliding against other materials. The friction coefficients of films grown by the new method (i.e. in Ar-C 60 and Ar-CH 4 plasmas) are comparable with those of natural diamond, and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can intermittently dominate friction and wear performance. Using results from a combination of TEM, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy, we describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of NCD films in dry N 2 . Finally, we suggest a few potential applications in which NCD films can improve performance and service lives.
Surface & Coatings Technology, 1997
In this study, we explored and compared the friction and wear performance of smooth (30 nm, root mean square) and nanocrystalline diamond films (average grain size = 15 nm) grown i3 an Ar-C6,, microwaveplastna with the friction a_nd wear performance of laserpolished microcrystalline diamond films (grain size = 20-50 pm) grown in a conventional CH4-H2 microwave plasma. Tribological tests were run under 2-N load in open air (30-50% relative humidity) and in dry Nz. The-frjctional performances of both the as-grown smooth and laser polished diamond films were comparable. They both afforded very low friction coefficients (0.06-0.15) and low wear rates (2-6 x IO-' mm3/N.m) to counterface Si3N4 balls. We used Raman spectroscopy, electron microscopy, and atomic force microscopy to ascertain the structural, chemical, and surface topographical characteristics of the films and cpflelated the-results with the friction and wear mechanisms of diamond films in open air and dry N2. 0 1997 Elsevier Science S.A.