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This paper is devoted to the optical emission studies of Octamethylcyclotetrasiloxane (OMCTS)/O2 derived, low pressure (0.1 Torr), 13.56 MHz RF plasmas. The emission is recorded with a resolution of 0.05 nm to two RF power densities of 0.25 and 0.50 W/cm2, at wavelengths of 180–1000 nm. Emitting atomic and molecular species in plasma are identified, and spatial variation in emission intensity is recorded through the space between electrodes. The hardness, elastic modulus, infrared absorbance, refractive index, and residual stress of the resulting plasma polymer films are presented. Most of the atomic and molecular emissions have been identified, and spectra can be used as a reference for OMCTS/O2 plasmas. Optical emission spectra are dominated by molecular CO, CO+, OH, and CO2+ bands, and atomic H and O lines. The absence of emissions from the Si, SiO, SiO2, CH, CH2, and CH3, together with the infrared absorbance of films, suggests that SiOxCy:H film formation occurs by way of the dissociation of C–H and Si–C bonds, as well as the polymerization of silica rings or long chains.

CrSiN coatings with different Si concentration (Si/(Cr + Si) ratio: 0, 3.7, 11.7, 20%) were deposited on stainless steel substrates using a closed field unbalanced magnetron sputtering (CFUBM) system. The variation in the microstructure of the films with the Si concentration was measured by XRD. The corrosion behavior of the CrSiN coatings in a deaerated 3.5% NaCl solution was investigated by potentiodynamic tests, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of the CrSiN film was found to depend on the Si concentration. The results of the potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr + Si) ratio. The EIS measurements showed that the corrosion resistance of the Si-bearing CrN was improved by the phase transformation of the film, which led to an increase in the pore resistance and charge transfer resistance. The Si-bearing CrN possesses the best corrosion resistance at a Si/(Cr + Si) ratio of 20%, measured by the maximization of the pore resistance and charge transfer resistance.

The formation and properties of WC–Ni thin films deposited on Si were studied. A cathodic tungsten carbide arc was used at room temperature to prepare the samples. In this paper, the effect of system parameters, such as external magnetic field, etc., were investigated. Without filtering, only condensed tungsten carbide droplets were observed on the substrate, while transparent films with few droplets were produced when a filter was used to reduce the number of macroparticles. Plasma floating potential and substrate current density were determined by voltage-current analyzer. The change of plasma states during cathodic arc discharges of tungsten carbide, under various magnetic fields of straight magnetic solenoid, was analyzed by optical emission spectroscopy (OES). In addition, an intensified camera system with a fiberoptically coupled high-resolution CCD was used for the estimating distribution of plasma density around the axis of the solenoid coil. Deposition rates of about 20 nm/min of WC–Ni film were determined with α-step. Scanning electron microscopy (SEM) was employed to determine the droplet distribution of the film and surface morphology. The surface roughness remained low over the whole coil current range with values between 0.2 μm at 100 A and 0.8 μm at 200 A.

Atmospheric plasma torch has many useful characteristics such as high current, high temperature and highly intensive radiation power. The performance of non-transferred plasma torch is significantly dependent on jet flow characteristics out of nozzle. Also, the compulsory swirl is being produced to gain the shape that can concentrate the plasma to the center of gas flow. In this study, the thermal flow characteristics of non-transferred plasma torch are investigated under atmospheric conditions. Numerical analyses are carried out with various inlet angles considering the swirl strength. In order to solve the governing equations, we have used a commercial code, CFD-ACE+ with FVM and SIMPLER algorithm. Furthermore, the size of flame is also experimentally investigated with various gas species.

Multilayered WC–Ti 1− x Al x N coatings were deposited on AISI D2 steel using cathodic arc deposition method. These coatings contain structural defects such as pores or pinholes. Thus, the substrate is not completely isolated from the corrosive environment. These growth defects in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion of the coatings was studied in deaerated 3.5 wt.% NaCl solution using classical electrochemical technique (potentiodynamic polarization test). Coating characteristics were examined by means of glow discharge optical emission spectroscopy, scanning electron microscopy, auger electron spectroscopy and transmission electron spectroscopy. The porosity was calculated from a result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the WC–Ti 0.6 Al 0.4 N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and reducing the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion reaction of coatings is caused by defects (pores, pinholes and crevices), coating delamination and galvanic effect between the droplet and the coating.

In the present work, multilayered coatings with alternate layers of WC-Ti and WC-Ti 1-x Al x N were deposited for use as wear-resistant and corrosion-resistant surfaces. Ti and TiN base layers were deposited on the substrate prior to the multilayers. WC-Ti 1-x Al x N coatings with variable Al content (i.e., Al target power density) were deposited onto a steel substrate (high-speed steel; HSS) by the cathodic arc deposition method. The Al content could be controlled using an evaporation source for Al and fixing the evaporation rate of the other target sources. Four kinds of WC-Ti 1-x Al x N coatings were prepared (WC-Ti 0.6 Al 0.4 N, WC-Ti 0.53 Al 0.47 N, WC-Ti 0.5 Al 0.5 N and WC-Ti 0.43 Al 0.57 N). The corrosion behavior of WC-Ti 1-x Al x N coatings in deaerated 3.5% NaCI solution was investigated by electrochemical corrosion tests and surface analyses. Particular attention was paid to the effects of Al content on the coating properties related to the corrosion behavior. The galvanic corrosion current measured between the coating and substrate showed a low value. The results of potentiodynamic polarization tests indicated that the WC-Ti 0.43 Al 0.57 N coating with lower porosity enhanced the corrosion resistance. In electrochemical impedance spectroscopy measurements, the WC-Ti 0.43 Al 0.57 N coating showed two time constants and decreased the charge transfer resistance of the coating (R et ). Multilayered coatings were analyzed by EDS and XRD techniques to evaluate the crystal structure and compound formation behavior. Surface and cross-sectional morphology of the films was observed using SEM. In addition, scratch tests were performed to measure film adhesion strength.

WC–(Ti1−xAlx)N coatings of stepwise changing Al concentration (WC–Ti0.86Al0.14N, WC–Ti0.72Al0.28N, and WC–Ti0.58Al0.42N) were deposited on AISI 1045 substrate by high-ionization sputtered PVD method. The Al concentration could be controlled by using evaporation source for Al and fixing the evaporation rate of the metals (WC alloy and Ti). The corrosion behavior of WC–(Ti1−xAlx)N coatings in deaerated 3.5% NaCl solution was investigated by electrochemical corrosion tests and surface analyses. Particular attention was paid to the effects of Al target power density on the film properties related to the corrosion behavior. The measured galvanic corrosion currents between coating and substrate indicated that WC–Ti0.72Al0.28N coating showed the best resistance of the coating tested. The results of potentiodynamic polarization tests showed that this coating had passivation and lower porosity. This indicated that this coating is effective in improving corrosion resistance. In electrochemical impedance spectroscopy, the WC–Ti0.72Al0.28N coating showed one time constant loop and the increased polarization resistance of coating relative to other samples. The better corrosion performance of WC–Ti0.72Al0.28N coating is due to the modified compactness, porosity and adhesion of the coating layer.

The corrosion behavior of Cr-N coated steels with different phases (α-Cr, CrN and Cr2N) deposited by cathodic arc deposition on AISI H13 steel was investigated in a 3.5% NaCl solution at ambient temperature. Potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were the techniques applied to characterize the corrosion behavior. It was found that the CrN coating had a lower current density from potentiodynamic polarization tests than others. The porosity, corresponding to the ratio of the polarization resistance of the uncoated and the coated substrate, was higher in the Cr2N coating than in the other Cr-N coated steels. EIS measurements showed, for most of the Cr-N coated steels, that the Bode plot presented two time constants. Also, the Cr2N coating represented the characteristic of Warburg behavior after 72 h of immersion. The coating morphologies were examined in planar view and cross-section by SEM analysis and the results were compared with those of the electrochemical measurement. The CrN coating had a dense, columnar grain-sized microstructure with minor intergranular porosity. From the above results, it is concluded that the CrN coating provided a better corrosion protection than the other Cr-N coated steels.

Co-WC is increasingly used for precision dies and punches in semiconductor assembly process. The enhancement of impact resistance of hard layer coatings on Co-WC dies and punches is crucial for the application of hard coatings such as TiN. In this study, Co-WC has been deposited with a TiN film after Ti bombardment at various bias voltages of 0–750 V using the cathodic arc ion plating process. The surfaces' etching morphology and the temperature increase upon pre-bombardment with Ti ion onto Co-WC were evaluated by SEM and in-situ monitoring, respectively. The increase of bias voltage over 500 V significantly induced selective etching of Co and enhanced the substrate temperature higher than 300 °C in 10 min, thereby promoting the formation of a dense TiN film onto it. The prior etching of the surface by Ti ion bombardment with a high bias voltage was very effective in improving the adhesion of the TiN film on Co-WC and therefore reduced plastic deformation and crack density around the indentation area in a Rockwell C indentation test. The impact failure of a TiN coating on Co-WC could be consequently reduced under loads up to 150 N.

A duplex surface treatment technique based on calorizing and plasma nitriding was developed to improve the wear and oxidation resistance of H13 steel at high temperatures. The effects of the relative thickness of the calorized layer to the depth of plasma nitriding on the wear and oxidation properties at temperatures up to 900 °C were investigated in this work. High-temperature wear tests were performed at 500 °C with dry conditions in open air using a ball-on-disk type tribotest machine. Isothermal oxidation tests were performed at 900 °C for up to 100 h under controlled atmosphere. The results indicated that the specimens with a calorized layer as an intermediate phase between the surface duplex layer and the base metal showed higher wear and oxidation resistance than the specimens with a nitrided layer alone. During exposure to elevated temperatures, the aluminum in the calorized layer diffused to the surface and formed an aluminum oxide layer. This oxide layer protected the specimens from further oxidation and prevented the nitrogen from diffusing out of the surface, thus resulting in the retention of surface hardness even after exposure to high temperatures.

Duplex plasma surface treatment by calorizing and plasma nitriding was carried out on mild steel and high alloyed tool steel to improve their elevated temperature wear properties. Effects of calorizing on the plasma nitriding behavior of the steels and the characteristics of the duplex-treated specimens were analyzed using SEM, EDS, XRD, and a microhardness tester. Calorizing on mild steel created a FeAl compound layer of approximately 120 μm thickness, resulting in the improvement of the surface hardness by a factor of 2. Subsequent plasma nitriding increased the surface microhardness above 1200 Hv (0.1 kgf) and the nitriding depth was of the order of 80 μm. The high alloyed tool steels showed a decrease in microhardness in the Al-diffused layer upon calorizing. The subsequent plasma nitriding, however increased the hardness up to 1280 Hv and the nitriding depth of over 80 μm was obtained. The room temperature wear resistance of the duplex-treated steels was slightly better than that of the nitrided one, but there was considerable improvement in the high temperature wear resistance at 500°C in the duplex-treated steels when both the wear volume and the weight change due to oxidation were considered.