Papers by Keyword: Plasma Electrolysis

Abstract: A novel aqueous plasma electrolysis applied for depositing a uniform and continuous Al₂O₃/Y₂O₃ ceramic coating on each fiber within a carbon fiber bundle are reported in this study. All equally spaced tungsten wires generated plasma arc, where the plasma was overlapped, excluded and extruded each other, finally a cylindrical plasma arc zone was formed, promoting the full coverage of the coating on each fiber. The Al₂O₃/Y₂O₃ coating protected the carbon fiber from oxidation above 850^oC. Similarly, the coating significantly improved the oxidation resistance of the carbon fiber with the mass loss of ~5% after isothermal oxidation in N₂ atmosphere at 800°C for 30 min, compared to ~14% of bare carbon fiber. By the movement of the T300 carbon fiber bundle, 1500 m coated carbon fiber bundle with the high-quality Al₂O₃/Y₂O₃ coating deposited on each fiber was successfully realized. It is believed that the novel aqueous plasma electrolysis will find a wide range of applications in modifying the interface of the carbon fiber reinforced composites. The present investigation will also open up a new horizon for preparing a protective coating on each fiber within two/three-dimensional carbon fiber fabric.

Abstract: Microhardness, friction coefficient, and wear rate of carburized titanium alloy VT 20 are considered. An X-ray diffractometer, a scanning electron microscopy (SEM) used to characterize the phase composition of the modified layer and its surface morphology. A pin-on-disc tribometer was occupied to evaluate wear behavior of the treated titanium alloys. It is established that the friction coefficient decreases from 0.46 (untreated sample) to 0.15 for the sample carburized at 750 °C during 5 min. Therefore, the anode carburizing of titanium alloys results in the reducing of the wear rate by 2 orders.

Abstract: Results of plasma electrolytic hardening and nitrohardening of medium carbon steels are discussed. The hardness of medium carbon steels after its plasma electrolytic quenching is HRC 56–62. The electrolytic heat-treatment in aqueous solution under pulse conditions can achieve different heating rates by varying the pulse periods and the ON:OFF ratios. The nitrogen diffusion decreases the austenitization temperature and results in formation of martensite after the sample cooling in the electrolyte. The aqueous solution that contained 15 wt.% NH₄Cl allows one to obtain the layer microhardness up to 1060 HV during 5 min at 750 °C. In this work, we investigate the corrosion resistance of the medium carbon steel which is obtained as a result of plasma electrolytic nitriding with following hardening in the same electrolyte. The cross-sectional microstructure, composition and phase constituents of modified layer under different processing conditions were characterized. It is shown that external oxide layer and nitrided layer promote the increase in the corrosion resistance. The maximal corrosion potential and minimal corrosion current density are observed after the nitriding of steels in the aqueous solution (11 wt.% of ammonium chloride and 11 wt.% of ammonium nitrate) at 750 °C during 5 min followed by the steel cooling in air.

Abstract: Features of the anode electrolytic plasma processing of commercial pure titanium and its alloys in aqueous solutions of ammonium chloride and ammonia additives are studied. It is identified that structure of modified layer contains an external TiO₂ or TiO layer with micropores of up to 100 nm and a diffusion sub-layer after nitriding in the solution with the ammonia addition. Some increase in the surface microhardness is found. The plasma electrolytic treatment of titanium makes it possible to enhance its corrosion resistance by short-term (5 min) saturation with nitrogen at 750 °C in an electrolyte containing 5% ammonia and 10% ammonium chloride. The oxide coating formed during the anodic treatment has a positive effect on the corrosion resistance of titanium and results in reduce of the corrosion rate by two orders under continuous tests. Saturation of titanium samples with nitrogen leads to an increase in their strength properties after corrosion tests with a slight decrease in ductility. An additional advantage of this coating is to reduce of leaching of alloying elements from samples in corrosive environments.

Abstract: In this paper, plasma electrolytic carburizing has been applied on the commercially pure titanium substrates in an organic based electrolyte with presence of some hard tungsten carbide nanoparticulates in suspension state. Pulsed current with variable duty cycle has been used for fabrication of functionally gradient nanocomposite coating. As a result, a hard nanocomposite layer has been formed on the surface of the samples with complex titanium carbide as its matrix and tungsten carbide nanoparticulates as its reinforced phase. In addition of used SEM, TEM and AFM for evaluation of coating nature, the presence of tungsten in different depths of formed layer has been followed by means of EDS. The effects of rate of variable duty cycle of applied pulsed current or treatment time have been described. Hardness profiles showed that the higher rates for variable duty cycles will cause lower hardness and sharper profilesThis document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.

Abstract: A carbontirided layer was produced on 20CrMnTi steel by plasma electrolytic carbonitriding (PEC/N). Scanning electron microscopy with an energy dispersive X-ray analysis was employed to study the morphology and chemical composition of the carbonitrided layer. Hardness of the layer was measured using a microhardness tester, and the phase structure was determined by X-ray diffraction. The results show that a compact carbonitrided layer can be obtained on the surface of 20CrMnTi steel. The thickness of the layer increases with carbontriding time. When the sample was treated at 120V for 20min, the thickness is 45μm and the highest microhardness is 766HV0.05. The carbontrided layers are composed of Fe3C, Fe5C2, ε-Fe3N and α-Fe.

Abstract: In this study, diffused carbon in workpiece surface with Plasma Electrolysis Carburizing (PEC) treatment applied to harden SAE 1015 steel is investigated. The workpiece is connected cathodically to a high current DC power supply that applies high voltage and uses stainless steel as the anode. After water ionization with this voltage, a hydrogen film forms around the workpiece. This film acts as a thermal and electrical insulation layer which increases the electric resistance around the workpiece and makes it being heated. The surface of the workpiece is transformed to austenite and after the disconnection of the current, the workpiece is quenched in aqueous solution. By the aid of this method, the workpiece can be hardened to 1200HV or more. In this paper, the effect of time and solution concentration on the depth of diffused carbon was studied. The hardness of workpiece was measured and the variation of the diffusion depth versus time and solution concentration was investigated.