Showing papers by "Xianting Zeng published in 1999"
TL;DR: In this paper, residual stress measurements of amorphous diamond-like carbon (DLC) coatings were obtained by studying the stress conditions of the substrate surface layer immediately adjacent to the coating via X-ray diffraction (XRD) with a thin film attachment.
Abstract: This paper presents residual stress measurements of amorphous diamond-like carbon (DLC) coatings obtained by studying the stress conditions of the substrate surface layer immediately adjacent to the coating via X-ray diffraction (XRD) with a thin film attachment. In such a set-up, the incidence angle α at which the primary beam strikes the specimen is fixed at a glancing angle (2° in our experiments) relative to the sample surface while the detector rotates to collect the diffracted X-rays. The amorphous carbon coatings were deposited on single-crystal silicon wafers and on polycrystalline KBr substrates in an unbalanced magnetron sputtering system. The effects of substrate material and deposition parameters on the internal stresses of the coatings are discussed in detail. XRD with thin film attachment provides a new and more precise way to determine the residual stresses in amorphous coatings. Increasing the relative nitrogen flow reduces the compressive stress level of the hydrogenated amorphous carbon coatings. Under the experimental conditions studied, higher substrate bias power and sputter power densities both increased the compressive stress level.
98 citations
TL;DR: In this paper, an optical emission monitor (OEM) was used to monitor and control the poisoning status of the targets during film deposition, and the nano-indentation hardness of 48 GPa was achieved in the coatings with an optimized superlattice wavelength of about 7 nm.
Abstract: TiN/NbN superlattice hard coatings were deposited using unbalanced magnetron sputtering technology. A gas manifold was used to generate a desired N2 partial pressure for each target, so as to produce stoichiometric TiN and NbN simultaneously. During film deposition, an optical emission monitor (OEM) was used to monitor and control the poisoning status of the targets. Under optimized deposition conditions, the TiN/NbN superlattice coatings deposited on high-speed steel substrates had a well-defined superlattice structure and sharp interfaces as well as stoichiometric composition. These coatings show high toughness, high elasticity and very high hardness, giving rise to significant improvements in tribological performance. The nano-indentation hardness of 48 GPa was achieved in the coatings with an optimized superlattice wavelength of about 7 nm. This super-high hardness coupled with high elasticity implies that TiN/NbN superlattice coatings could be ideal for tools application, especially in the stamping/cutting tooling industry.
50 citations
TL;DR: In this paper, the authors reported on the deposition of carbon composite coatings on high speed steel substrates using simultaneous unbalanced magnetron sputtering of metallic and graphite targets.
Abstract: Carbon composite coatings combine high hardness and toughness, good adhesion, low friction coefficient, and low wear rate. These properties make it a good candidate for tribological applications. Previous studies commonly used hydrocarbon gases to produce metal (Ti, W, Cr) doped amorphous carbon coating (M–a:C–H) and sputtered Ti–TiN or TiCN as supporting layers. Relatively high hardness and good adhesion could be obtained by optimizing the composition and structure of the supporting layers and by increasing the doping level. However, the friction coefficient increased with the doping level, which resulted in high wear rates. This article reports on the deposition of carbon composite coatings on high speed steel substrates using simultaneous unbalanced magnetron sputtering of metallic and graphite targets. The coating consists of a graded Cr–Ti–N alloyed interlayer and a Cr-containing carbon composite surface layer. Raman spectroscopy, scanning electron microscopy, nanoindentation, scratch tests and pin-o...
17 citations