The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the g...The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the gas tungsten arc welding process and using nickel as the wetting agent. Samples from the weld band, heat-affected zone and parent metal region were extracted precisely and DC/AC electrochemical tests in combination with techniques such as scanning electron microcopy and energy dispersive spectrometry were conducted. The results of the electrochemical tests show that the corrosion resistance of the parent metal sample is higher than that of the welded composite and the HAZ samples. However, as the corrosion potential （Eco^r） of the parent metal is more positive than other two samples, this becomes the cathode in galvanic couples with two other samples. On the other hand, the weld composite sample is also cathodic due to its more positive Ecorr compared to HAZ sample. This means that the HAZ can be particularly at risk of preferential dissolution. The approach can be used in specific areas on plain carbon steel to locally increase hardness and resistance to abrasion and reduce manufacturing costs.展开更多
The etching resolution of electrochemical fabrication technique is influenced significantly by the diffusion layer of the etchant. It has been shown that a fast etching rate can achieve higher etching resolution due t...The etching resolution of electrochemical fabrication technique is influenced significantly by the diffusion layer of the etchant. It has been shown that a fast etching rate can achieve higher etching resolution due to so-called heterogeneous scavenging effect, while a lower etching rate will result in rather lower etching resolution. For the latter case, the confined etchant layer technique(CELT) has been employed to improve the etching resolution. i. e., a certain redox couple which can consume the etchant homogeneously and rapidly was added to the solution. The homogeneous scavenging effect confined the etchant within a narrow layer around the electrode surface and much improved etching resolution was achieved. Using the CELT and a needle-shaped microelectrode, an etching spot of several micro-meters was obtained at silicon wafer surface.展开更多
文摘The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the gas tungsten arc welding process and using nickel as the wetting agent. Samples from the weld band, heat-affected zone and parent metal region were extracted precisely and DC/AC electrochemical tests in combination with techniques such as scanning electron microcopy and energy dispersive spectrometry were conducted. The results of the electrochemical tests show that the corrosion resistance of the parent metal sample is higher than that of the welded composite and the HAZ samples. However, as the corrosion potential （Eco^r） of the parent metal is more positive than other two samples, this becomes the cathode in galvanic couples with two other samples. On the other hand, the weld composite sample is also cathodic due to its more positive Ecorr compared to HAZ sample. This means that the HAZ can be particularly at risk of preferential dissolution. The approach can be used in specific areas on plain carbon steel to locally increase hardness and resistance to abrasion and reduce manufacturing costs.
文摘The etching resolution of electrochemical fabrication technique is influenced significantly by the diffusion layer of the etchant. It has been shown that a fast etching rate can achieve higher etching resolution due to so-called heterogeneous scavenging effect, while a lower etching rate will result in rather lower etching resolution. For the latter case, the confined etchant layer technique(CELT) has been employed to improve the etching resolution. i. e., a certain redox couple which can consume the etchant homogeneously and rapidly was added to the solution. The homogeneous scavenging effect confined the etchant within a narrow layer around the electrode surface and much improved etching resolution was achieved. Using the CELT and a needle-shaped microelectrode, an etching spot of several micro-meters was obtained at silicon wafer surface.
