Measurement and optimization of atmospheric plasma sprayed CoMoCrSi coatings parameters on Ti-6Al-4V substrates affecting microstructural and properties using hybrid abductor induction mechanism

A hybrid artificial intelligence method (AIM) is used to optimize the atmospheric plasma spraying (APS) processing parameters for CoMoCrSi coatings deposited on Ti-6Al-4V substrates. In the proposed approach, the Taguchi design method is used to obtain an initial solution for the optimal set of APS parameters. The true optimal values of the spray distance, chamber pressure, current, argon gas flow rate and hydrogen gas flow rate are then obtained using an artificial neural network (ANN) and genetic algorithm (GA). The coatings deposited using the processing parameters determined using the Taguchi design method alone have a porosity of 8.5%. However, following the ANN/GA optimization procedure, the porosity reduces to just 5.6%. The XRD analysis results show that the as-sprayed coatings contain Cr₃Si phase as a result of the high-temperature plasma flame. In addition, it is shown that the structure of the Ti phase in the coating transforms from a α-Ti crystal structure (i.e., HCP) to a β-Ti crystal structure (i.e., BCC) during thermal treatment at temperatures to 1200 °C. Finally, it is shown that the hardness of the annealed coatings increases with both an increasing annealing time and an increasing annealing temperature. The higher hardness under higher temperature conditions is attributed to the precipitation of Cr₃Si phase. Overall, the coatings obtained in the present study using the optimal spray-coating parameters have a low porosity, a high hardness and a good thermal stability at high temperatures.     

Comparison of influences of NaCl and CaCl2 on the corrosion of 11% and 17% Cr ferritic stainless steels during cyclic corrosion test

During the drying stage of the cyclic corrosion test on ferritic stainless steels in the NaCl environment, the current abruptly increased and then decreased to nearly zero, indicating that pits are initiated as the salt concentration is increased, which are then repassivated when the surface is completely dry. During the wet stage, the current remained high, suggesting that pits mainly propagate during the wet stage. In contrast, in the cyclic corrosion test in the CaCl₂ environment, the current was highest during the drying stage, indicating that the electrolyte is not completely dried and corrosion mainly propagates during the drying stage.     

Use of the gold markers method to predict the mechanisms of iron atmospheric corrosion

Iron corrosion under atmospheric conditions has been investigated by using the gold markers method. The corrosion experiments were performed in a climatic chamber with an accelerated treatment. The gold markers localization, carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, revealed that the rust layer growth was essentially due to an internal development. Moreover, microRaman mappings allowed prediction of the mechanism of rust layer evolution during the ageing treatment. Finally these results were compared to samples corroded for several 100 years in order to extrapolate our observations to long term corrosion.     

Evaluation of Adhesion Improvement of a GFRP Treated with Atmospheric Plasma Torch

The applications (and repair) of glass fiber reinforced epoxy composites are increasing in different industries (wind turbines, boats, chassis of buses, etc.) due to specific strength and low cost. Their major disadvantage is the difficulty to shape complex components. This problem can be solved manufacturing different parts, being adhesively bonded afterwards. This work studies the effect of atmospheric pressure plasma torch compared to grit-blasting to improve adhesion. After surface treating different parts, the changes of wettability and surface energy were measured. Treated samples were bonded with polyurethane and epoxy adhesives, and the quality of the bond was evaluated using pull-off adhesion tests and fracture strength test under cleavage loads. Obtained results allow to select the most adequate treatment in terms of mechanical requirements.     

AM60镁合金大气腐蚀及动力学分析

研究了铸态和挤压态AM60镁合金在太原地区的大气腐蚀行为。试验结果表明铸态合金的腐蚀速率高于挤压态合金。铸态合金中的共晶组织比α-Mg更具耐大气腐蚀能力,但是这导致了共晶相周围的α-Mg相腐蚀严重,且腐蚀产物膜也不均匀,保护性差。挤压态合金的最大腐蚀深度要远小于铸态合金。挤压态合金的显微组织比铸态更加均匀,而且不含有共晶组织,导致挤压态合金表面的腐蚀产物膜更加致密也更具有保护性。挤压变形不会引起AM60镁合金大气腐蚀性能的下降。     

Separation of Enantiomeric Triacylglycerols by Chiral‐Phase HPLC

Liquid chromatography–atmospheric pressure chemical ionization mass spectrometry (LC–MS/APCI) with a chiral phase was used for separation of triacylglycerols (TAG) obtained either by organic synthesis or isolated from different algal species. We present chromatographic characteristics and tandem mass spectra of enantiomers and positional isomers (regioisomers) of C16, C18 and C20 polyunsaturated fatty acids. The retention time was found to depend on the structure of the given TAG, increasing with increasing number of double bonds and decreasing with increasing number of the carbons in TAG, with the exception of dieicosapentaenoyl‐palmitoyl‐glycerols.     

大型常压储罐罐顶的宏观检查

从大型常压储罐安全运行的现实需求出发,将罐顶宏观检查分为整体性检查、表面检查和附件检查三个部分,并给出每个部分具体可操作的检验项目。宏观检查对于大型常压储罐的安全运行有着重要的意义。     

Evolution mechanism of the microstructure and mechanical properties of plasma-sprayed yttria-stabilized hafnia thermal barrier coating at 1400 °C

Yttria stabilized hafnia (Hf_0.84Y_0.16O_1.92, YSH16) coatings were sprayed by atmospheric plasma spraying (APS). The effects of thermal aging at 1400 °C on the microstructures, mechanical properties and thermal conductivity of the coatings were studied. The results show that the as-sprayed coating was composed of the cubic phase, and the nano-sized monoclinic (M) phase was precipitated in the annealed coating. The presence of M phase effectively constrained the sintering of the coating due to its superior sintering-resistance. The Young's modulus kept at a nearly same level of ~78 GPa even after annealing, and the coating annealed for 6 h yielded a maximum value of hardness but revealed a declining tendency in the Vicker's hardness with prolonged sintering time. The thermal conductivity increased from 0.8-0.95 W m^-1 K^-1 at as-sprayed state to 1.6 W m^-1 K^-1 after annealing at 1400 °C for 96 h. The dual-phase coating is promising to serve at temperatures above 1400 °C due to its excellent thermal stability and mechanical properties.     

Carbonation of Mg powder to enhance the corrosion resistance of Mg-rich primers

This paper is a continuation of our investigation into the characteristic dichotomy of Mg-rich primers between accelerated salt-fog testing and natural weathering. Our earlier study suggested that magnesium powder reacted with atmospheric CO₂ to form a protective carbonate layer on its surface. In this study, magnesium powder was treated with aqueous carbonic acid to accelerate magnesium carbonate development. The treated magnesium powder was formulated into a Mg-rich primer and evaluated for its corrosion resistance. The Mg-rich primer formulated with the treated Mg powder performed better in the salt-fog test than the control primer based on untreated Mg powder.     

利用大气能见度获取多波长气溶胶光学特性

介绍了一种利用测量得到的大气能见度获取多波长气溶胶光学特性(主要探讨气溶胶的消光系数、散射系数和吸收系数)的新方法。首先,由能见度求出波长0.55 μm的大气消光系数,在减去大气分子的消光系数后得到0.55 μm气溶胶的消光系数,使用Mie散射理论求出气溶胶粒子的数密度;因为同一时间大气状态下气溶胶的数密度是不变的,所以再次使用Mie散射理论即可得到其他波长下气溶胶的光学特性。以1.06、1.536、3.75 μm为例,给出了合肥2003年近地面层的气溶胶光学特性,该方法对于研究大气环境和大气中光传输模式具有重要意义。