Papers by Keyword: Hard Coating

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Authors: Xin Tan, Yu Qing Li, Xue Jie Liu, De Gong Liu
Abstract: The structural and elastic properties of HfN and Hf-Si-N have been studied, using first principles calculations based on the density functional theory. These calculations provide the lattice parameter, cohesive energy and elastic constants of fcc (NaCl)-HfN, the N-deficient Hf-Si-N and the Hf-deficient Hf-Si-N solution phase. In order to study the relative stability, binding energy of all configurations has been calculated. The results showed that it was difficult to add a Si atom into the center of the HfN cell because the cohesive energy decreased. However, if an Hf atom or an N atom was missing in the HfN, a silicon atom was possible to occupy the vacant site and form the Hf-Si-N substitutional solid solution. Moreover, the bulk modulus, shear modulus and elastic modulus increased accordingly, the mechanical properties were improved.
Authors: Day Shan Liu, Yu Ko Liao, Cheng Yang Wu, Fuh Shyang Juang, Ching Ting Lee
Abstract: A hard coating silicon oxide film was deposited on flexible substrates by a PECVD system. Tertramethylsilane (TMS) and oxygen were employed as raw materials. Surface roughness and hardness of these films deposited under various TMS/O2 gas flow ratio, rf power and chamber pressure were investigated. At adequate fabricated conditions, the original surface roughness of PMMA (~ 3.36 nm) and PC (~ 1.38 nm) substrates was markedly flatted to 1.52 and 0.39 nm, respectively. Meanwhile, the surface hardness of coated PMMA and PC substrates was also enhanced to 6.077 GPa and 3.978 GPa, respectively. The hardness of silicon oxide film deposited by TMS-PECVD system was superior to silicon oxide films prepared from e-beam evaporation and dipping technologies.
Authors: Li Ming Yu, Yue Ma
Abstract: Hard coating can be used as damping treatment. An interfacial damping model, based on the interface slip mechanism, is presented. Interfacial damping ( ) can be expressed as a quadratic function of the interface adhesion strength (N). It means that there exists a suitable bonding strength ( ) which makes the interfacial damping capacity obtain the maximum value. The model can be used to evaluate the damping performance and the interfacial adhesion condition of a hard coating structure.
Authors: Uwe Zschenderlein, B. Kämpfe, Bernd Schultrich, Gudrun Fritsche
Abstract: Internal stresses are very important for the performance of protective hard coatings. Tensile stresses favour the formation and propagation of cracks, inducing fracture and corrosion. Medium compressive stresses hinder fatigue. But high compressive stresses, typically for hard coatings produced by PVD (physical vapour deposition) processes, support delamination in order to relax the stored elastic energy. However notwithstanding its relevance, the internal stresses are only seldom used for the optimisation and quality control of hard coatings in industry. This unsatisfying situation is caused by the deficit in efficient measuring methods. The results of thin sheets, where the stresses can be simply measured by their curvature, are not necessarily representative for the coating of thicker parts. The conventional XRD (X-ray Diffraction), based on angle-dispersive evaluation needs expensive devices and is rather time consuming. The energy-dispersive technique opens new possibilities. It is based on polychromatic radiation. The interference of the lattice plane reflections corresponding to the Bragg-equation is investigated by the diffraction intensity of the different wavelength (or photon energies), not by varying the Bragg-angle as in conventional XRD. Hence, the whole diffraction pattern can be obtained in one shoot without the use of any goniometer. This allows the construction of small and compact measuring devices and the reduction of measuring time to a few minutes. The capability of the ED-XRD (Energy Dispersive X-ray Diffraction) is demonstrated for titanium nitride and chromium nitride films deposited by cathodic vacuum arc with varying parameters. Comparisons were made with the much more time-consuming AD-XRD (Angle Dispersive X-ray Diffraction) for residual stress analysis. The results of both methods are in good agreement.
Authors: Dušan Petković, Miloš Madić, Miroslav Radovanović, Predrag Janković
Abstract: It is well known fact that materials play an important role in engineering design. Nowadays over a hundred thousand available materials can be distinguished with constant tendency for increasing the novel designed materials. Therefore material selection process becomes a complex and time consuming task. Selection of the most suitable material for a given application can be regarded as a multi-criteria decision making (MCDM) problem with conflicting and diverse objectives. New MCDM methods have been developed, and existing methods improved, showing that research in the decision-making is important and still valuable. This paper describes the use of recently developed MCDM methods, i.e. Complex Proportional Assessment (COPRAS) and Weighted Aggregated Sum Product Assessment (WASPAS) for selecting the most suitable hard coating material.
Authors: Ping Zhang, Jing Hua Jiang, Ai Bin Ma, Ze Hua Wang, Yu Ping Wu, Ping Hua Lin
Abstract: With the aim to obtain the high cavitation-erosion-resistance coating for the surface safeguard of fluid machinery, two kinds of hard coatings (WC-Cr-Co and Cr3C2-NiCr) were prepared on 1Cr18Ni9Ti substrate by high velocity oxy-fuel spraying (HVOF), which microstructure and performance were investigated respectively by optical microscope, X-ray diffraction, Vickers hardness, scanning electron microscope (SEM), and vibratory cavitation apparatus. The results indicated that these two coatings had the higher hardness and the finer structure than ZG06Cr13Ni5Mo, which is used actual in water conservancy. The results of cavitation erosion continued for 39 hours presented that the mass loss of WC-Cr-Co and Cr3C2 -NiCr coatings increased ceaselessly with time, and the cavitation erosion speeds varied with time. Compared with ZG06Cr13Ni5Mo, their cavitation erosion resistance performances were better due to their higher hardness and finer structure, and WC-Cr-Co coating was much better than Cr3C2-NiCr coating. Obviously, the higher hardness and finer structure could strengthen the cavitation erosion resistance of coating materials.
Authors: Wei Yu Ho, Pin Hua Hsu, Chien Liang Lin
Abstract: Aluminum chromium nitride (AlCrN) coatings and aluminum chromium oxynitride (AlCrON) coatings were successfully fabricated through cathodic arc deposition with pulsed bias. The results indicated that both AlCrN and AlCrON coatings had a lower coefficient of friction against AISI 52100 bearing ball under dry conditions than CrN coating. The hardness of the AlCrN coating was in the range of 30 GPa, two times higher than that of the AlCrON coating. Thermogravimetric and differential scanning calorimetry analyzer (TGA/DSC) confirmed the best thermal stability of the AlCrON coating during the test.
Authors: Branko Skoric, Damir Kakas, Aleksansar Miletic
Abstract: In this paper, we present results of a study of TiN films which are deposited by Physical Vapor Deposition and Ion Beam Assisted Deposition. In the present investigation the subsequent ion implantation was provided with N2+ ions. The ion implantation was applied to enhance the mechanical properties of the surface. The film deposition process exerts a number of effects such as crystallographic orientation, morphology, topography, densification of the films. The evolution of the microstructure from porous and columnar grains to densely packed grains is accompanied by changes in mechanical and physical properties. A variety of analytic techniques were used for characterization, such as scratch test, calo test, SEM, AFM, XRD and EDAX. The experimental results indicated that the mechanical hardness is elevated by penetration of nitrogen, whereas the Young’s modulus is significantly elevated. Thin hard coatings deposited by physical vapour deposition (PVD), e.g. titanium nitride (TiN) are frequently used to improve tribological performance in many engineering applications. Ion bombardment during vapour deposition of thin films, colled ion beam assisted deposition (IBAD), exerts a number of effects such as densification, changes in grain size, crystallographic orientation, morphology and topography of the films. This paper describes the successful use of the nanoindentation technique for determination of hardness and elastic modulus. In the nanoindentation technique, hardness and Young’s modulus can be determined by the Oliver and Pharr method. Therefore, in recent years, a number of measurements have been made in which nanoindentation and AFM have been combined.
Authors: Wei Yu Ho, Chi Wei Chen, Da Yung Wang, Woei Yun Ho
Abstract: In this study, TiAlSiN coatings were synthesized by cathodic arc deposition with Ti and Al88Si12 dual cathodes. The as-deposited coatings were following with post-deposition heat treatment in air and nitrogen atmosphere, respectively, at the temperature of 400 oC for 3 hour. The annealing treatment of the TiAlSiN coating has an expected effect on the wear resistance and cutting performance. The TiAlSiN coating subjected to heat treatment in nitrogen atmosphere presented the best oxidation and wear resistance among the tested coatings. The friction coefficient of the TiAlSiN coatings subjected in nitrogen atmosphere at 400oC was decreased due to the effect of the structure modification by increasing hardness. Using thermogravimetric analyzer (TGA), the result turned out the lowest weight change of TiAlSiN coating after annealing treatment in air if compared to that of all the coatings. The reason my be due to the oxide layer formed on the coating surface acted as a protective layer. Cutting test on the hardened steel with mist oil lubricants, the TiAlSiN-coated WC-Co tool with annealing treatment in nitrogen provides the best wear resistance at the cutting edge.
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