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Titanium diboride was deposited on the surface of spot-welding electrodes for zinc coated steel sheets due to its high electrical and thermal conductivity and potential to prolong the lifespan of the electrodes, and mass of the el...
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Titanium diboride was deposited on the surface of spot-welding electrodes for zinc coated steel sheets due to its high electrical and thermal conductivity and potential to prolong the lifespan of the electrodes, and mass of the electrodes was measured after every 30 s during depositing. The results showed that the as-deposited electrodes are losing their mass during the process, which is completely different from the deposition of TiC. Evaporation of copper and oxidation of TiB2 at high temperature generated by electrosparking play the most important roles in the mass loss. Cutting and flaking of the brittle coating also contribute to the mass loss. The cracks within the coating are channels for the leakage of the evaporated substrate material. The mass of the electrodes decreases as the pulse energy increases with the voltage increasing. Pre-coated nickel contributes to the mass loss of the electrodes too.
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In the conventional electro spark alloying (ESA), the workpiece is mechanically connected to the discharge circuit of the pulse generator as the cathode and the treating electrode acts as the anode. A novel addition to ESA process...
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In the conventional electro spark alloying (ESA), the workpiece is mechanically connected to the discharge circuit of the pulse generator as the cathode and the treating electrode acts as the anode. A novel addition to ESA processing is to include the workpiece electrically in series to the discharge circuit of the pulse generator by discharge through two inter electrode gaps using double treating electrode. The electrical parameters of pulse and electrode materials were investigated to find out under which conditions mass could be deposited on workpiece from both treating electrodes, one was connected as anode and other as cathode. As a result of experiments, an asymmetry in erosion of the treating electrodes was observed, because mass transfer from electrode to specimen was always less when the electrode was cathode than when the electrode was anode. The asymmetry in erosion of treating electrodes could be eliminated by employing a power supply generating symmetrical bipolar pulses that switch polarity of treating electrodes periodically. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 8]
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A new electrospark deposition (ESD) process, electrospark- computer numerical control deposition (ES-CNCD), was proposed based on an ES-computer integrated deposition system (ES-CIDS). The ES-CIDS integrated a 3-axis CNC milling m...
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A new electrospark deposition (ESD) process, electrospark- computer numerical control deposition (ES-CNCD), was proposed based on an ES-computer integrated deposition system (ES-CIDS). The ES-CIDS integrated a 3-axis CNC milling machine with an ESD welder via a passive exsertile/retractable pattern special deposition holder. The ES-CNCD process employs high-current electrical pulses of short duration to modify the metal surface. In this work, an AlCoCrFeNi high-entropy alloy (HEA) was used as the electrode to prepare HEA coatings on TC11 titanium alloy substrate via weld-spot pattern deposition strategy. Three quantities of cathode mass gain (CMG), anode mass gain (AMG) and material transfer coefficient (MTC) were redefined for ES-CNCD process. The impact of process parameters on CMG, AMG, MTC was investigated via designing orthogonal experiments. The physical mode of mass transfer of ES-CNCD process has been proposed and confirmed by experiments. (C) 2016 Elsevier B.V. All rights reserved.
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The results of investigation of the thickness and microhardness of electrospark coatings (ESCs) of amorphous and nanocrystalline alloys (NCAs) are presented. It is shown that the application of amorphous and NCAs as electrode mate...
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The results of investigation of the thickness and microhardness of electrospark coatings (ESCs) of amorphous and nanocrystalline alloys (NCAs) are presented. It is shown that the application of amorphous and NCAs as electrode materials increases the thickness of ESCs and the produced coatings are characterized by high hardness.
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This study is a summary of a series of experimental investigation of electrospark alloying (ESA) by the application of pulse currents with amplitudes and durations ranging from 100 to 1000 angstrom and from 25 to 4000 mu s, respec...
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This study is a summary of a series of experimental investigation of electrospark alloying (ESA) by the application of pulse currents with amplitudes and durations ranging from 100 to 1000 angstrom and from 25 to 4000 mu s, respectively. The technological parameters of coating, such as mass transfer, and number of deposition layers till its failure and corresponding properties of coating, such as thickness, roughness and uniformity, etc. were investigated. To prevent the destruction of the already superimposed deposition during ESA, it is necessary to limit the time of processing before the beginning of its fracture. It was experimentally shown that, processing time till fracture could be determined by not only the cross-sectional examination of coating, but simultaneously with some distinctive characteristic of coating parameters, precisely, by the mass transfer coefficient. Since the processing time till the fracture has limit, the amount of mass transferred from treating electrode (anode) to substrate (cathode), that is, the thickness of coating is restricted. The analysis from the thickness point of view was carried out and some approaches to show the possibility to increase it by ESA technique were proposed. (c) 2006 Elsevier B.V. All rights reserved.
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Buildup of precipitation hardened nickel base superalloys by electro spark deposition due to the lowheat input of the process hasmany attractions. Characterization of the microstructure of the ESD built up layer of IN738LC over an...
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Buildup of precipitation hardened nickel base superalloys by electro spark deposition due to the lowheat input of the process hasmany attractions. Characterization of the microstructure of the ESD built up layer of IN738LC over an as-cast basemetal is accomplished in thiswork. The grain structure and solidification texture of the coating are investigated by orientation imaging microscopy (OIM), optical and scanning electron microscopy. It is shown that the deposited layer is formed mainly through epitaxial nucleation and growth on the base metal structure while discontinuities acting as nucleation sites produce fine grains with independent orientations. It is shown that such independent grains can have a significant role in improving the integrity of the ESD built up layer, since they can act as crack arrest sites and make the coating more resistant to the propagation of liquation and solidification fissures. Moreover, it is found that nanosized γ′ precipitates exist in the coating indicating the high tendency of γ′ for precipitation even in the extremely high cooling rates involved in the ESD process. Hardness measurements indicated a higher hardness for the built up layer which is attributable to the finer microstructure of the coating.
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A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark...
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A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark pulse energy. A splattered porous morphology was observed in the surface layer, and underneath this, a uniform superfine columnar gamma phase structure with a column width of about 0.6 mu m. When exposed at 1000 deg C, theta-Al_2O_3 formed rapidly in the early oxidation stage. After 100h oxidation, a large amount of theta-Al_2O_3 was still present, and a dense and adherent, thin alpha-Al_2O_3 scale had formed beneath it.
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摘要 :
A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark...
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A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark pulse energy. A splattered porous morphology was observed in the surface layer, and underneath this, a uniform superfine columnar gamma phase structure with a column width of about 0.6 mu m. When exposed at 1000 deg C, theta-Al_2O_3 formed rapidly in the early oxidation stage. After 100h oxidation, a large amount of theta-Al_2O_3 was still present, and a dense and adherent, thin alpha-Al_2O_3 scale had formed beneath it.
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摘要 :
A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark...
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A MCrAlX-type coating has been prepared by electrospark deposition (ESD) and its isothermal oxidation behavior studied. The results indicate that deposition rate and surface roughness of the coatings increase with increasing spark pulse energy. A splattered porous morphology was observed in the surface layer, and underneath this, a uniform superfine columnar gamma phase structure with a column width of about 0.6 mu m. When exposed at 1000 deg C, theta-Al_2O_3 formed rapidly in the early oxidation stage. After 100h oxidation, a large amount of theta-Al_2O_3 was still present, and a dense and adherent, thin alpha-Al_2O_3 scale had formed beneath it.
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Nano- and microstructured electrodes WC-8%Co were used for electrospark deposition (ESD) of coatings onto an Armco iron upon variation in the energy P of single discharge pulses between 0.01 and 1.2 J. Considered are the physical ...
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Nano- and microstructured electrodes WC-8%Co were used for electrospark deposition (ESD) of coatings onto an Armco iron upon variation in the energy P of single discharge pulses between 0.01 and 1.2 J. Considered are the physical and chemical processes taking place at the surface of electrodes: in the coating formed on a substrate (cathode), and in the secondary structure of electrode (anode). The resultant coating was found to contain largely an amorphous phase and tungsten semicarbide W2C. In case of nanostructured electrodes, an increase in P above some threshold value gives rise to an increasing content of crystalline phases and formation of a structure comprising of sub-micron W2C/WC grains surrounded by an amorphous binder. In case of microstructured electrodes, the amount of the amorphous phase is predominant for any P. The use of nanostructured electrodes in ESD onto an Armco iron substrates seems expedient only for P<0.23 J. (C) 2008 Elsevier B.V. All rights reserved.
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