Papers by Keyword: PVD

Abstract: Titanium nitride (TIN) films were prepared by using rf magnetron sputtering technique. The films were deposited by a pure N₂ plasma sputtering. Their mechanical properties, such as nanoindentation hardness, friction coefficient, and wettability have been investigated. XRD studies revealed that the orientation of TiN films changes toward the (111) orientation with decreasing working pressure due to a strong compressive stress during deposition . The strongest TiN(111) orientation is found when the film is deposited at working pressure of 1pa. This film shows a largest hardness of 15 GPa and a smallest friction coefficient of 0.17. This film was also found to be accompanied by a water-repellent surface with a water contact angle more than 100^°

Abstract: Despite its high tensile strength and its brilliant fatigue behaviour, 7075-T6 aluminium alloy usage is dramatically reduced, due to its sensitivity to corrosion and its poor surface characteristics. In order to be adopted for advanced applications in the aeronautic, automotive and maritime fields, as well as in further innovative applications, 7075-T6 resistance must be improved. Controversial results are found in literature on coated 7075-T6 fatigue strength, due to the complex mechanical interaction between the substrate and the coating, and the high temperatures involved in the coating process. In the present work, testing on rotating bending fatigue (R = -1) 7075-T6 uncoated and PVD DLC coated specimens has been conducted. Different stress levels were considered, to assess the impact of the applied stress on the fatigue life of the substrate-coating system. SEM characterization of the fracture surfaces has been performed, to investigate the influence of the coating on the fracture mechanism

Abstract: Nano size (2 - 10 nm) metal particles were formed and accumulated on powder substrate by conventional physical vapor deposition (PVD) process, in which the powder were a non-volatile in vacuum, such as Al₂O₃ powder. The neutral nuclei which were formed on the substrates from vaporized or sputtered metal atoms at an initial thin film growth were not grown up to coalescence and island stage with arrival atoms and ad-atom migration in the continuous deposition process, when the powder in vessel were continuously stirred during the deposition. Nano sized particles on the polymer chips (diameter: 1-2mm) easily dispersed into the polymer matrix by heating the chips, and on non-soluble powder, g-Al₂O₃, were stuck on the supporters stably in air. The nanoparticles on sucrose directly formed colloid with water solvents without dispersive agents. Most of the nano sized particles appear their own characteristic colors due to plasmon effect. Concentration and size of the nanoparticles are controlled by physical parameters in the PVD and the stirring speed of the powder. Surface phenomena on the substrate have been discussed with TEM, SEM, EDX, UV spectroscopy, etc. comparing with the conventional thin film growth.

Abstract: The wear properties of steel dental curettes coated with wear resistant Diamond Like Carbon (DLC) and metal nitride coatings deposited by Physical Vapor Deposition (PVD) were studied by using a customized mechanical device simulating motion and load of dental curettes against human teeth. The wear surfaces were studied by optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Nanoindentation. Rockwell indentation testing was used to evaluate the coating adhesion. With the optimized combination of substrate steel and wear resistant coating reduction of 80% in the wear of instruments could be achieved.

Abstract: The main objective of this paper is to offer ion-plasma technology for production of Ti (titanium) and titanium nitride (TiN) erosion-resistant nanocoatings for the machine building products, which ensures the coatings with optimum and stable properties. As a result of experiments and processing experimental data the optimum composition of ion-plasma titanium and titanium nitride nanocoatings was obtained and offered.The approbation of the developed technology on the existing machine building products (compressor blade of the helicopter gas turbine; base material: Incoloy 800) was carried out. The comparative study on the influence of the coating on the surface quality, coefficient of friction, adhesion strength and erosion resistance was done. For evaluation of the obtained nanocoating surface’s quality 2D and 3D surface description approaches were applied. Achieved results prove the effectiveness of offered ion-plasma technology for production of titanium and titanium nitride erosion-resistant nanocoatings with appropriate and stable properties.

Abstract: Engineering industries are currently using many tool materials such as ceramic,carbide, high speed steel, Cubic Boron nitride and diamond. In most of the small scale industries, the lathe machines are consuming High Speed Steel (HSS) Tool. The HSS tools are easily available and cheapest one. In this present investigation, the Tungsten HSS Single point cutting tool was taken as substrate material. Two substrate HSS Tools were coated with two different combinations of TiAlN composite material using Physical Vapour Deposition coating technique. The surface roughness and hardness were determined for the tools in same condition. The tools were used in lathe machine in same operating condition. The weights of the tools were checked using standard equipment after each machining trials. The loss of tool weight for each trial was determined and the percentage of weight loss was calculated. The life of the Titanium Aluminium Nitride (Ti 70% , Al 25%) coated tool increased by 3.74 times than uncoated tool. The life of the Titanium Aluminium Nitride (Ti 55% , Al 35%) is increased by 2.71 times than uncoated HSS tool.

Abstract: High strength-to-mass ratio light alloys, such as 7075-T6 aluminium alloys and Ti-6Al-4V titanium alloys, are commonly adopted for high performance structural components in the aeronautic, automotive and maritime sectors. For this reason, it is crucial to investigate the effects of the external environment on their mechanical properties, to avoid dramatic component failure. In the present work, experimental tests were performed on Ti-6Al-4V and 7075-T6 light alloys. Ti-6Al-4V notched flat dogbone specimens, with K_t = 1.18, were tested for quasi-static and SCC effects in a methanol-water aggressive environment at different concentrations. Rotating bending R = -1 fatigue tests were performed on 7075-T6 in air and methanol environment, to evaluate the effects of an aggressive environment on the fatigue strength at 200’000 cycles. The influence of DLC and WC/C PVD coatings on fatigue limit at 200’000 cycles has been evaluated in air and aggressive environment, to assess their mechanical and protective effects on the 7075-T6 substrate

Abstract: PVD hard coating is a well-known surface treatment technology for steels to improve wear resistance and, to some extent, corrosion resistance. In principle, hard coating can be carried out for Al alloys, but due to the natural oxide layer and the insufficient load-bearing capacity of the soft base material, the application of this technology for wear protection of components is not regarded as being particularly promising. The research activities described in this paper focused on electron beam (EB) surface alloying with a Co-based additive, and the influence of two different hardness levels (270HV0.1 and 390HV0.1) on the improvement of the local load-bearing capacity of Al alloys with thin PVD hard coatings. A further focus of this research was on the material-specific aspects of the coating deposition. Compared to steels, the hard coated surface of Al alloys is rougher and the measured adhesion of the coating is significantly lower. For this purpose, different technological PVD parameters (e.g. Ti interlayer, deposition temperature, and time) were adapted to optimize the coating properties – especially adhesion. The paper deals with comparative studies of single (PVD hard coating of Al base material) and duplex treatment (EB alloying of Al base material and subsequent PVD hard coating) by means of improvement of the coating and compound hardness, friction and wear behavior (pin-on-disc test), as well as the corrosion resistance (potentiodynamic measurements in 0.05M H₂SO₄). While the level of improvement in wear resistance as a result of the duplex treatments strongly depended on the adhesion of the thin coatings, the corrosion behavior was strongly influenced by the PVD deposition process and coating thickness.

Abstract: Modeling of thin film coating is an important work to identify the required characteristic. In general, suitable coating process parameters are very important to find the best characteristics of coating and towards less material usage, reduced trial in experiment and less machine maintenance. In this paper, Response Surface Methodology (RSM) was implemented in modeling TiN coating grain size. N₂ pressure, Argon pressure, and turntable speed were selected as process variables, while the coating grain size as an output response. Significant factors that influence the coating characteristic are determined by using Analysis of Variance (ANOVA) and to develop a polynomial quadratic model. Findings from this study suggested that turntable speed and Argon pressure quadratic term has significant effect to the TiN coating grain size. The result also showed that the actual validation data fell within the 95% prediction interval (PI) and the residual errors percentage was lower than 10%.

Abstract: 7075-T6 aluminium alloy is commonly adopted in high performance structures and components. Its fatigue behaviour is however dramatically worsened by exposure to aggressive environments. The deposition of PVD coatings, which are commonly adopted to increase the surface properties of structural elements in terms of hardness, contact fatigue and wear resistance, could be beneficial also for the fatigue behaviour of a 7075-T6 substrate in an aggressive environment. In the present work, Diamond Like Carbon (DLC) PVD coated 7075-T6 specimens immersed in methanol have been analysed, by means of step-loading rotating bending fatigue tests (R = -1) at 2·10⁵ cycles. Coated specimens were tested in laboratory air for comparison, and uncoated polished samples were studied in both the environments to obtain reference values. SEM micrographs of the fracture surfaces were taken to investigate the effects of the corrosive environment on the failure mechanism.