Effect of surface morphology on the frictional behaviour of hot filament chemical vapour deposition diamond films

Abstract

A novel deposition method combining the conventional hot filament chemical vapour deposition method and the polishing technique is proposed for fabricating ultra-smooth composite diamond (USCD) films onto cobalt cemented tungsten carbide substrates. SEM and AFM investigations show that the deposited USCD films have ultra-smooth and uniform surface, and their surface roughness values are measured by using an AFM and a surface profilometer as Ra∼ 59 and ∼88.8 nm, respectively. The tribological properties of USCD films are examined in comparative friction tests with a microcrystalline diamond (MCD), fine-grained diamond, and polished MCD films, and the effect of surface morphology on the friction behaviour of diamond films is highlighted. Friction tests show that the polished MCD and USCD films exhibit very low friction coefficients of approximately 0.08, 0.12, and 0.17, while dry sliding against counterfaces of alumina ceramic, ball-bearing steel, and copper materials. Intensive interactions between two surfaces of the mating parts result in gradual blunting of the sharp tips of diamond crystallites and accumulation of wear debris on the worn surface of diamond films. Adhered wear debris on the diamond films are supposed to have a significant influence on their frictional behaviour because they will cause increasing adhesive strength between the mating surfaces, and thus a higher friction coefficient for the contact.

Deposition and Characterization of Boron-Doped HFCVD Diamond Films on Ti, SiC, Si and Ta Substrates

“…The tantalum wires are used as the hot filaments, the parameters of which have been optimized in order to obtain uniform temperature field distribution on the wafer substrate surface in previous study (filament number=6, diameter=0.8mm, filament separation=17mm, filament-substrate distance=9mm) [11]. A direct current bias is applied between the filament and substrate to enhance the nucleation density during the deposition [12]. The detailed deposition parameters are as stated in Table 1.…”

Effect of Hot Filament Chemical Vapor Deposition Filament Distribution on Coated Tools Performance in Milling of Zirconia Ceramics

“…It is softer than fully sintered ZrO 2 and can still be machined using conventional methods such as milling, but its hardness level is significantly higher than pre-sintered materials. Diamondcoated cutting tools made by h filament chemical vapor deposition (HFCVD) have many excellent properties, including high hardness [9], exceptional thermal conductivity [10], and low friction [11], as well as a low expansion coefficient [12], and this coating technology is considerably less expensive and allows for greater flexibility in tool geometry. The diamond-coated tools for zirconia ceramic workpiece machining are anticipated to have a significantly longer tool life and produce a superior machining quality than that of non-coated tools.…”

Development and growth time optimization of boron-doped micro-crystalline, undoped micro-crystalline and undoped nano-crystalline composite diamond film

“…In most of the wear-resistant and anti-frictional applications, the severe working condition and the production quality control put forward extremely high requirements for the surface roughness of the diamond film and it is of great significance to smooth the surface because it is supposed that for the ultra-hard diamond film, the lower surface roughness often means the less frictional resistance, lower frictional coefficient and lower wear rate. 16 Micro-sized diamond grains and high surface roughness of either the undoped micro-crystalline diamond (UMCD) film or the BDMCD film can cause remarkable mechanical scratches on the surfaces of the counterparts, and thus these films are completely unsuitable to be directly applied when cold-drawing soft materials, such as aluminum and copper. Nanocrystallization is an effective approach to refine diamond grains and reduce the surface roughness, 17 so the nano-crystalline diamond (NCD) film has attracted increasing interests.…”