The influence of sulphate-reducing bacteria biofilm on the corrosion of stainless steel AISI 316

This work investigates microbially-influenced corrosion (MIC) of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate. The biofilm and pit morphology that developed with time were analyzed using atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results were interpreted with an equivalent circuit to model the physicoelectric characteristics of the electrode/biofilm/solution interface. D. desulfuricans formed one biofilm layer on the metal surface, while the marine isolate formed two layers: a biofilm layer and a ferrous sulfide deposit layer. AFM images corroborated results from the EIS modeling which showed biofilm attachment and subsequent detachment over time.     

Effects of coating thickness and residual stresses on the bond strength of ASTM C633-79 thermal spray coating test specimens

Wire-arc-sprayed nickel-aluminum is widely used in the aircraft industry for dimensional restoration of worn parts and as a bond coat for thermal barrier coatings and other top coats. Some repair applications require thick coatings, which often result in lower bond strength. A mechanism being investigated to ex-plain this decrease in bond strength is the free edge effect, which includes both coating residual stresses and coating thickness. The layer-removal method was used to determine experimentally the residual stresses in wire-arc-sprayed nickel-aluminum coatings of different thicknesses. Bond strength evalu-ations were performed using an improved ASTM C 633-79 test specimen. Finite-element analysis and fracture mechanics were used to investigate the effects of coating thickness and residual stress state on coating bond strength.     

Influence of chromium on the local structure and morphology of ferric oxyhydroxides

The extended X-ray absorption fine structure (EXAFS) method and transmission electron microscopy (TEM) have been used for characterizing the local structure and morphology of ferric oxyhydroxides, α-FeOOH and γ-FeOOH, with and without chromium. These ferric oxyhydroxide powders were prepared from aqueous solutions containing iron and chromium ions. Radial structural functions for iron obtained by Fe K edge EXAFS spectra showed that the linkage of structural units formed by FeO₆ octahedra in γ-FeOOH is distorted by chromium addition, while such distortion in α-FeOOH is not clearly detected. On the other hand, Cr K edge EXAFS spectra showed that the local structure around chromium does not necessarily correspond to the local structure around of iron, which is observed by Fe K edge EXAFS spectra. This suggests that the structural units containing iron and chromium are heterogeneously distributed in these ferric oxyhydroxides. The local structural information was discussed coupled with morphological features of these ferric oxyhydroxides observed by TEM.     

基于I2C总线技术的等离子喷焊系统的研究

阐述了基于I^2C总线技术的等离子喷焊过程控制系统的设计原理，介绍了软硬件及接口设计技术。实践表明，采用I^2C总线技术，不仅使系统的芯片大大减少，系统的灵活性增强，而且提高了系统的抗干扰能力。     

Impact of transient chemistry on the corrosion potential of a steam turbine disc steel

The adoption of two-shifting in coal-fired power generation (switching from on-load to off-load conditions on a daily basis and off-load for the weekend) results in regular cycling of the solution chemistry of the condensed steam on the turbine discs. A first stage investigation has been made of the effect of such chemistry cycling on the corrosion potential of the disc steel. The corrosion potential is typically about +0.05 V (SCE) in off-load chemistry (aerated pure water) and below −0.6 V (SCE) in on-load chemistry (deaerated solution containing chloride or chloride and sulphate anions). The critical observation was the sluggish response of the corrosion potential upon restoration of deaerated on-load conditions with the implication of a likely increase in pit and stress corrosion crack development.     

Effects of electrical discharge surface modification of superalloy Haynes 230 with aluminum and molybdenum on oxidation behavior

The effects of the electrical discharge alloying (EDA) process on improving the high temperature oxidation resistance of the Ni-based superalloy Haynes 230 have been investigated. The 85 at.% Al and 15 at.% Mo composite electrode provided the surface alloying materials. An Al-rich layer is produced on the surface of the EDA specimen alloyed with positive electrode polarity, whereas, many discontinuous piled layers are attached to the surface of the EDA superalloy when negative electrode polarity is selected. The oxidation resistance of the specimen alloyed with positive electrode polarity is better than that of the unalloyed superalloy, and the effective temperature of oxidation resistance of the alloyed layer can be achieved to 1100 °C. Conversely, the oxidation resistance of the other EDA specimen alloyed with negative electrode polarity is even worse than that of the unalloyed superalloy.     

Leaded brass rods C 38500 for automatic machining operations: A technical report

C 38500 is a widely used copper alloy with a great variety of applications from decoration and architecture to mechanical/electrical engineering. The chemical composition of this alloy offers superior machinability and subsequently increased productivity in high-speed machining and manufacturing processes. In European countries, this alloy is used primarily as free cutting brass (CW 614N according to EN 12164: 1998), similar to C 36000 alloy, which is used also for thread rolling. The lower percentage of Cu compared to C 36000 (nominal 58% instead of 61%) decreases the cost of the raw materials. This paper reports the principal aspects of microstructure, mechanical properties, and machinability of this alloy in relation to the industrial manufacturing process used.     

Evaluation of the coupled multielectrode array sensor as a real-time corrosion monitor

Coupled multielectrode array sensors made of carbon steel and stainless steels were evaluated and compared with electrochemical noise (EN) sensors. Good correlations between sensor signals and solution corrosivity were observed for all multielectrode array sensors. Some correlation between the average pit index and solution corrosivity was observed for the carbon steel EN sensors, but not for the stainless steel EN sensors. The time-average noise resistances from the stainless steel EN sensors correlate well with solution corrosivity. There were, however, large random fluctuations and drifting for all EN signals, which make the EN sensors unreliable as real-time monitors.     

基于STM32的逐阳帆控制系统设计

针对传统太阳能跟踪系统现场调试复杂、可靠性不够高的问题,提出一种基于STM32的太阳能跟踪系统设计。该系统为单轴跟踪系统,通过获取太阳能板的地理位置和当前时间信息用一定算法算出太阳的方位角,驱动电机,实现对太阳的跟踪;采用基于Zig Bee技术的无线通讯系统,具有群簇控制能力,简化现场调试过程;通过Mod Bus协议实现控制系统信息上报,便于后台管理;提供多种工作模式,提高系统的抗风、抗雪性能;通过在控制芯片片内Flash写入备份程序,保证系统主程序出现问题后,系统跳转至备份程序继续运行,提高系统的可靠性。在实际现场应用中,该系统具有系统运行稳定、升级维护方便、使用寿命长的特点。