Tribological behaviors of Fe-Al-Cr-Nb alloyed layer deposited on 45 steel via double glow plasma surface metallurgy technique

Double glow plasma surface metallurgy technique was used to fabricate a Fe?Al?Cr?Nb alloyed layer onto the surface of the 45 steel. The microstructures and composition of th?eA Fl?eCr?Nb alloyed layer were analyzed by scanning electronic microscopy, X-ray diffraction and energy dispersive spectroscopy. The results indicate thatthe 20 μm alloyed layer is homogeneous and compact. The alloyed elements exhibit a gradient distribution along the cross section. Microhardness and nanoindentation tests imply that the surface hardness of the alloyed layer reaches HV 580, which is almost 2.8 times that of the substrate. Compared with the substrate, the alloyed layer has a much smaller displacement and a larger elastic modulus. According to the friction and wear tests at room temperature, the? FeAl?Cr?Nb alloyed layer has lower friction coefficient and less wear mass, implying that the Fe?Al?Cr?Nb alloyed layer can effectively improve the surface hardness and wear resistance of the substrate.

Iridium Coating Deposited by Double Glow Plasma Technique——Effect of Glow Plasma on Structure of Coating at Single Substrate Edge

Double glow plasma technique has a high deposition rate for preparing iridium coating. However, the glow plasma can influence the structure of the coating at the single substrate edge. In this study, the iridium coating was prepared by double glow plasma on the surface of single niobium substrate. The microstructure of iridium coating at the substrate edge was observed by scanning electron microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy and X-ray diffraction. There was a boundary between the coating and the substrate edge. The covered area for the iridium coating at the substrate edge became fewer and fewer from the inner area to the outer flange-area. The bamboo sprout-like particles on the surface of the substrate edge were composed of elemental niobium. The substrate edge was composed of the Nb coating and there was a transition zone between the Ir coating and the Nb coating. The interesting phenomenon of the substrate edge could be attributed to the effects of the bias voltages and the plasma cloud in the deposition chamber. The substrate edge effect could be mitigated or eliminated by adding lots of small niobium plates around the substrate in a deposition process.

CO_2 Reforming of CH_4 by Atmospheric Pressure Abnormal Glow Plasma

A novel plasma atmospheric pressure abnormal glow discharge was used to investigate synthesis gas production from reforming methane and carbon dioxide. Special attentions were paid to the discharge characteristics and CH4, CO2 conversion, H2, CO selectivity, and ratio of H2/CO varied with the changing of discharging power, the total flux, and the ratio of CH4/CO2. Experiments were performed in wider operation variables, the discharging power of 240 to 600 W, the CH4/CO2 of 0.2 to 1.0 and the total flux of 140 to 500mL/min. The experiments showed that the conversion of CH4 and CO2 was up to 91.9% and 83.2%, the selectivity of CO and H2 was also up to 80% and 90% and H2/CO mole ratio was 0.2 to 1.2, respectively. A brief analysis for discharge characteristics and the experimental results were given.

Tribological Behavior of Magnesium Alloy AZ91 Coated with TiN/CrN by Arc-glow Plasma Depositing

With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of magnesium alloy to static components. In this study, a 2 μm thick coating with 12 sub-layers of CrN and TiN is deposited alternately on the surface of magnesium alloy AZ91 by a novel method of arc-glow plasma depositing to improve its wear resistance. The composition and microstructure of the coating layer are analyzed by means of SEM, XRD and GDS. The friction coefficient is measured by ball on disc rubbing test, and the wear rates are also calculated. The results indicate that the friction coefficient is increased, but the wear rate is dropped sharply as compared with bare metal. The surface hardness is about HK0.01 1400.

Study on Mo Diffusion in Double Glow Plasma Surface Molybdenizing of Ti_2AlNb

Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries due to its high specific strength and fracture toughness as well as excellent creep resistance. However, insufficient wear-resistance is the main drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy is carried out as an attempt to resolve this problem. This paper deals with the effects of key process parameters on the diffusion behavior of Mo. The composition distribution and microstructare of the alloying layer are analyzed by SEM, XRD and GDS. Micro-hardness distribution profile is measured along the distance from surface to center. The results indicate that both the temperature and the processing time have significant effects on the diffusion process. Finally, the dif- fusion coefficient at optimized temperature of 980℃ is calculated through regression analysis.

Platinum and Iridium Coatings Obtained by Double Glow Plasma Technology

Pt and Ir coatings were produced by double glow plasma technology on the surface of Ti alloy substrates. The chemical compositions of the coatings were determined by X-ray diffraction and X-ray photoelectron spectroscopy. The microstructure and morphology of the coatings were observed by scanning electron microscopy. The hardness and elastic modulus of the coatings were estimated by nanoindentation. The measurements of adhesive forces of the coatings were performed with scratch tester. The results indicated that the Pt and Ir coatings displayed the preferred (220) orientation due to the initial nuclei with preferred growth on the surface of the substrates. The interface between the Pt coating and substrate exhibited no evidence of delamination. The Ir coating was composed of irregular columnar grains with many nanovoids at the interface between the coating and substrate. The mean values of hardness for Pt and Ir coatings were 0.9 GPa and 9 GPa, respectively. The elastic modulus of Pt and Ir coatings were 178 GPa and 339 GPa, respectively. The adhesive forces of the Pt and Ir coatings were about 66.4 N and 55 N, respectively. The Pt and Ir coatings adhered well to the Ti alloy substrates.

Best Magnetic Condition to Generate Hollow Cathode Glow Plasma in High Vacuum

Based on magnetron hollow cathode discharge, the magnetic condition of glow plasma generation in high vacuum, including both direction and magnitude of the applied mag- netic field, is theoretically derived and experimentally evaluated in this paper. Single particle orbital theory is introduced to discuss the possibilities to generate glow plasma at gas pressure under 10-2 Pa when the magnetic field direction is parallel or perpendicular or oblique to the electric field direction. A quantitative estimation criterion of magnetic induction intensity is also proposed in theory. The comparison with experiments suggests that glow plasma in high vacuum will form more easily in oblique magnetic field condition and that the criterion is accurate enough to estimate magnetic induction intensity at a certain gas pressure.

Nitrogen Removal from Molten Steel under Argon DC Glow Plasma

Under argon DC glow plasma, the nitrogen removal from molten steel was studied. The experimental result showed that nitrogen mass percent could be reduced to 0000 8%. The change of polarity had no impact on nitrogen removal when the nitrogen mass percent was low. The mechanism of denitrogenation of molten steel under argon DC glow plasma was discussed.

Influence of the Electrode Distance on Microstructure and Corrosion Resistance of Ni-Cr Alloyed Layers Deposited by Double Glow Plasma Surface Metallurgy

Ni-Cr alloyed layers were synthesized on the surface of Q235 mild steel by double-glow plasma surface metallurgy with different electrode distance.The microstructure and phases of the alloyed layer were characterized by scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),and X-ray diffraction(XRD).The corrosion behavior of the Ni-Cr alloyed layers both in 3.5%NaCl and 0.5 M H_(2)SO_(4) solution were systematically investigated by open-circuit potential(OCP),potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The obtained results reveal that the Ni-Cr alloyed layer consists of a deposited layer and an inter-diffusion layer.With increasing the electrode distance,the relative thickness,microstructure and phase composition of the Ni-Cr alloyed layers vary greatly.Polarization data show the Ni-Cr alloyed layer with the electrode distance of 15 mm has highest corrosion resistance and lowest corrosion rate,while EIS results reveal the same trend.The highest protective efficiency in 3.5%NaCl and 0.5 M H_(2)SO_(4) solution are 99.23%and 99.92%,respectively,obtained for the Ni-Cr alloyed layer with 15 mm electrode distance.When the electrode distance is too large,a thin and porosity Ni-Cr alloyed layer,caused by low plasma density and Kirkendall effect,will be obtained,and will decrease the protective efficiency in corrosive medium.

Double Glow Plasma Surface Alloyed Burn-resistant Titanium Alloy

Conventional titanium alloy may be ignited and burnt under high temperature, high pressure and high gas flow velocity condition. In order to avoid this problem, we have developed a new kind of burn-resistant titanium alloy—double glow plasma surface alloying burn-resistant titanium alloy. Alloying element Cr , Mo, Cu are induced into the TJ-6A1-4V and Ti-6.5Al-0.3Mo-l.5Zr-0.25Si substrates according to double glow discharge phenomenon, Ti-Cr ,Ti-Mo, Ti-Cu binary burn-resistant alloy layers are formed on the surface of Ti-6Al-4V and Ti-6.5Al-0.3Mo-l.5Zr-0.25Si alloys. The depth of the surface burn-resistant alloy layer can reach to above 200 microns and alloying element concentration can reach 90%. Burn-resistant property experiments reveal that if Cr concentration reach to 14%, Cu concentration reach to 12%, Mo concentration reach to 10% in the alloying layers, ignition and burn of titanium alloy can be effectively avoided.

perimental Study on the Interaction of Electromagnetic Waves and Glow Plasma

An experimental system was established in order to study the interaction between electromagnetic waves, with a frequency of 300 kHz to 3 GHz, and DC glow discharge plasma. The results show that the DC glow discharge plasma affects the transmission properties of elec- tromagnetic waves, while the waves can change both temperature and density of electrons.

Growth mechanism of polycrystalline Ir coating by double glow plasma technology

Pure Ir coating was produced by double nism of the Ir coating was investigated. glow plasma technology. Growth mecha- The Ir coating was composed of irregular compacted columnar grains with lots of nanovoids appeared on the interface between the coating and the substrate. The Ir coating was polycrystalline with a preferred （220） orientation due to the initial nuclei with preferred growth on the surface of the substrate. The formation mechanism of the Ir coating depended on kinetic adsorp- tion and diffusion process with nucleation, coalescence and thickness growth. At the beginning of the deposition process, the growth mode of the coating was mainly con- trolled by the nucleation rate. Due to the low substrate temperature resulting in low mobility of the deposited atoms, some micropores and nanoviods were present at the interface. With the deposition process, the substrate temperature was increased and then kept steady. The growth of the coating was governed by the growth rate. The high substrate temperature supported enough energy to surface mobilitv of adatoms.

Corrosion property of copperized layer on Zr formed by double glow plasma surface alloying technique

Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma surface alloying technique was used for copperizing on pure Zr surface.Besides,X-ray diffraction（XRD）,scanning electron microscope（SEM） and energy dispersion spectrum（EDS） were employed to characterize the samples.Furthermore,research was also conducted on the polarization curve of the samples in different solutions.Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % Na Cl and 0.5 moláL-1Na OH solutions.Especially in 0.5 moláL-1Na OH solution,the corrosion resistance can achieve significant improvement.However,copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 moláL-1H2SO4 solution.The results may provide new insight into way for improving the corrosion property of zirconium alloys.

TREATMENT OF METALS, POLYMER FILMS, AND FABRICS WITHA ONE ATMOSPHERE UNIFORM GLOW DISCHARGE PLASMA(OAUGDP) FOR INCREASED SURFACE ENERGY AND DIRECTIONAL ETCHING

Direct exposure of samples to the active species of air generated by a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) has been used to etch and to increase the surface energy of metallic surfaces, photoresist, polymer films, and nonwoven fab- rics. The OAUGDP is a non-thermal plasma with the classical characteristics of a DC normal glow discharge that operates in air (and other gases) at atmospheric pres- sure. Neither a vacuum system nor batch processing is necessary. A wide range of applications to metals, photoresist, films, fabrics, and polymeric webs can be accom- modated by direct exposure of the workpiece to the plasma in parallel-plate reactors. This technolopy is simple, it produces effects that can be obtained in no other way at one atmosphere; it generates minimal pollutants or unwanted by-products; and it is suitable for individual sample or online treatment of metallic surfaces, wafers, films, and fabrics. Early exposures of solid materials to the OAUGDP required minutes to produce rela- tively small increases of surface energy. These durations appeared too long for com- mercial application to fast-moving webs. Recent improvements in OAUGDP gas com- position, power density, plasma quality, recireulating gas flow, and impedance match- ing of the power supply to the parallel plate plasma reactor have made it possible to raise the surface energy of a variety of polymeric webs (PP, PET PE etc.) to levels of 60 to 70 dynes/cm with one second of exposure. In air plasmas, the high surface ener- gies are not durable, and fall to 50 dynes/cm after periods of weeks to months. Here, we report the exposure of metallic surfaces, photoresist, polymeric films, and nonwo- ven fabrics made of PP and PET to an impedance matched parallel plate OAUGDP for durations ranging from one second to several tens of seconds. Data will be re- ported on the surface energy, wettability, wickability, and aging effect of polymeric films and fabrics as functions of time of exposure, and time after exposure; the rate and uniformity of photoresist etching; and the production of sub-micron structures by OAUGDP etching at one atmosphere.

Application of the Multi-Electrode in the Degradation of Alizarin Red Induced by Glow Discharge Plasma

This paper presents a novel set-up to be used in the degradation of dye, Various influencing factors, such as the voltage, the number of the anodes, and the catalytic action of Fe^2＋, were examined. Chemical oxygen demand （COD）, ultraviolet （UV）, FTIR absorption spectra, and atomic force microscopy （AFM） were used to monitor the degradation process. The results showed that the efficiency of degradation is raised by increasing the applied voltage, and is further improved when two or three anodes are used. Moreover, the use of Fe^2＋ ion can promote the degradation reaction and shorten the degradation time. So the multi-electrode instrument is more efficient in degrading the dye and should be further studied.

Low Pressure DC Glow Discharge Air Plasma Surface Treatment of Polyethylene (PE) Film for Improvement of Adhesive Properties

The present work deals with the change in surface properties of polyethylene （PE） film using DC low pressure glow discharge air plasma and makes it useful for technical applications. The change in hydrophilicity of the modified PE film surface was investigated by measuring contact angle and surface energy as a function of exposure time. Changes in the morphological and chemical composition of PE films were analyzed by atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. The improvement in adhesion was studied by measuring T-peel and lap-shear strength. The results show that the wettability and surface energy of the PE film has been improved due to the introduction of oxygen-containing polar groups and an increase in surface roughness. The XPS result clearly shows the increase in concentration of oxygen content and the formation of polar groups on the polymer surface. The AFM observation on PE film shows that the roughness of the surface increased due to plasma treatment. The above morphological and chemical changes enhanced the adhesive properties of the PE＇film surfaces, which was confirmed by T-peel and lap-shear tests.

Degradation of Anionic Dye Eosin by Glow Discharge Electrolysis Plasma

This paper describes a novel method for the degradation of eosin by using glow discharge electrolysis （GDE）. The effects of various parameters on the removal efficiency were studied. It was found that the eosin degradation could be raised considerably by increasing the applied voltage and the initial concentration, or by decreasing pH of the aqueous solution. Fe^2＋ ion had an evident accelerating effect on the eosin degradation. The degradation process of eosin obeyed a pseudo-first-order reaction. The relationship between the degradation rate constant k and the reaction temperature T could be expressed by Arrhenius equation with which the apparent activation energy Ea of 14.110 kJ· mol^-1 and the pre-exponential factor k0 of 2.065× 10^-1 min^-1 were obtained, too. The determination of hydroxyl radical was carried out by using N, N-dimethyl -p-nitrosoaniline （RNO） as a scavenger. The results showed that the hydroxyl radical plays an important role in the degradation process.

Oxidative Degradation of 4-chlorophenol in Aqueous Induced by Plasma with Submersed Glow Discharge Electrolysis

The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined by high performance liquid chromatography （HPLC）. Various influencing factors such as the initial pH, the concentration of 4-CP and the catalytic action of Fe^2＋ were examined. The results indicate that 4-CP is eventually degraded into inorganic ion, dioxide carbon and water. The attack of hydroxyl radicals on the benzene rings of 4-CP in the initial stage of oxidative reactions is presumed to be a key step. They also suggest that the reaction is of a pseudo-first order kinetic reaction and the proposed method is an efficient way for the 4-CP degradation,

Exploration to generate atmospheric pressure glow discharge plasma in air

Atmospheric pressure glow discharge（APGD） plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge（DBD） in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in airgap is suppressed effectively and a large space of APGD plasma in air is generated. Further,through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.

A Review on Chemical Effects in Aqueous Solution induced by Plasma with Glow Discharge

Chemical effects in different aqueous solutions induced by plasma with glow discharge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..