Abstract:A new and exciting technique for performing DLC deposition on the inside of cylindrical substrates, in particular pipes, will be described. Using the hollow cathode effect (HCE), a high density plasma can be generated within such cylindrical substrates by using Plasma Enhanced Chemical Vapor Deposition (PECVD). As the pipe itself is the vacuum chamber, such high density plasmas can be maintained by using asymmetric bipolar direct current (DC) pulsed power. Very high deposition rates can thus be achieved of the… Show more
“…Therefore, the increased fatigue strength of the DLC‐coated specimens can be attributed to the crack initiation resistance enhanced by DLC coating. The DLC films deposited by PECVD have Vickers hardness of about 2200 5 and good adhesion to the substrate regardless of film thickness. Consequently, it is believed that such high hardness and good adhesion of the DLC films effectively acted to suppress the premature crack initiation due to inclusion cracking or slip deformation in the substrate, leading to the higher fatigue strength of the DLC‐coated specimens than the substrate specimen.…”
A B S T R A C T Rotating bending fatigue tests have been performed using Diamond-like carbon (DLC) coated specimens of a wrought magnesium alloy, AZ80A, in laboratory air and demineralised water and the effect of DLC coating on fatigue and corrosion fatigue behaviour was studied. Three film thicknesses of 3.5 μm, 13 μm, and 25 μm (two-layer film) were evaluated and particular attention was paid to the role of thick DLC coating. In laboratory air, the fatigue strengths of the DLC-coated specimens were higher than that of the substrate specimen and increased with increasing film thickness. This was because hard DLC coating with good adhesion suppressed the crack initiation due to cracking of inclusions or cyclic slip deformation on the substrate surface. In demineralised water, the fatigue strength of the 3.5-μm DLC-coated specimen was the same as that of the substrate specimen due to the penetration of the water through pre-existing film defects, while the 13-μm and 25-μm DLC-coated specimens showed increased corrosion fatigue strength with increasing film thickness and also exhibited nearly the same fatigue strength as in laboratory air except for a few premature failed specimens, indicating a potential of thick DLC coating or two-layer coating for complete improvement of corrosion fatigue strength in aqueous environments.
“…Therefore, the increased fatigue strength of the DLC‐coated specimens can be attributed to the crack initiation resistance enhanced by DLC coating. The DLC films deposited by PECVD have Vickers hardness of about 2200 5 and good adhesion to the substrate regardless of film thickness. Consequently, it is believed that such high hardness and good adhesion of the DLC films effectively acted to suppress the premature crack initiation due to inclusion cracking or slip deformation in the substrate, leading to the higher fatigue strength of the DLC‐coated specimens than the substrate specimen.…”
A B S T R A C T Rotating bending fatigue tests have been performed using Diamond-like carbon (DLC) coated specimens of a wrought magnesium alloy, AZ80A, in laboratory air and demineralised water and the effect of DLC coating on fatigue and corrosion fatigue behaviour was studied. Three film thicknesses of 3.5 μm, 13 μm, and 25 μm (two-layer film) were evaluated and particular attention was paid to the role of thick DLC coating. In laboratory air, the fatigue strengths of the DLC-coated specimens were higher than that of the substrate specimen and increased with increasing film thickness. This was because hard DLC coating with good adhesion suppressed the crack initiation due to cracking of inclusions or cyclic slip deformation on the substrate surface. In demineralised water, the fatigue strength of the 3.5-μm DLC-coated specimen was the same as that of the substrate specimen due to the penetration of the water through pre-existing film defects, while the 13-μm and 25-μm DLC-coated specimens showed increased corrosion fatigue strength with increasing film thickness and also exhibited nearly the same fatigue strength as in laboratory air except for a few premature failed specimens, indicating a potential of thick DLC coating or two-layer coating for complete improvement of corrosion fatigue strength in aqueous environments.
“…Recently, the hollow cathode effect could achieve high deposition rates for a-C:H thin films of up to 1 μm min −1 on the internal surface of cylindrical geometries [17]. However, the geometry where the effect is obtained does not allow the massive application of such thin films.…”
Diamond-like carbon (DLC) is a metastable form of amorphous carbon with attractive properties such as high hardness, low friction, chemical inertness and high wear resistance. In this work, hydrogenated amorphous carbon (a-C:H) thin films were deposited using a plasma enhanced chemical vapor deposition technique by pulsed DC plasma with a simple, low-cost and efficient arrangement of multi-cathodes and multi-anodes in order to enhance the plasma by electrostatic confinement. The samples were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Elastic Recoil Detection Analysis, Raman Spectroscopy, and nanoindentation measurements. a-C:H thin films show an homogeneous hydrogen profile along the films deposited at −600 V and −800 V and variable working pressure. According to Raman spectra, both the I D /I G ratio and the G-peak position increase at higher voltages (more remarkable dependence) and lower working pressures (less remarkable dependence). Moreover, the hardness depends on working conditions such as power supply voltage and total working pressure. The electrostatic confinement enhances the deposition rates of a-C:H thin films up to values of 0.9 μm·h −1 , which is almost double than those previously published by pulsed DC plasma in similar conditions. The Raman spectra follow the stage 2 of an established model and this structure transition may explain the hardness behavior.
“…These coatings can be processed with various deposition methods [4][5][6]. On an industrial scale the PlasmaEnhanced-Chemical-Vapor-Deposition (PECVD) method is a frequent technique to deposit hard and wear resistant hydrogenated amorphous carbon coatings (a-C:H) for high load applications [7][8][9]. Coating systems produced by PECVD often exhibit low adhesion strength to the substrate because of high internal stresses [10].…”
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