Interface reaction between alloys and submerged entry nozzle controlled by an electric current pulse

To solve the limitations of clogging and erosion of the submerged entry nozzle (SEN) for the production of high-quality special steel, the chemical reactivity between different alloys and the SEN and the interface reaction between alloys and the SEN controlled by an electric current pulse (ECP) were examined in this study. Results revealed that the chemical reactivity between different alloys and the SEN is different. For example, the reactivity between rare-earth metal and the SEN was strong, while that between Al and the SEN was extremely weak. At the same time, some differences between the clogging and interface reaction by ECP control were observed. Typically, at the positive electrode of the SEN, when a stable and dense clogging layer is formed, the internal SEN was effectively protected. However, at the negative electrode of the SEN, the decarburization rate of the SEN was accelerated by ECP, probably leading to a vicious circle of accelerated clogging and erosion of the SEN. Therefore, in the future, issues of clogging, erosion, infiltration, and decarbonization between active alloys and the SEN in the casting process may be solved and regulated by using the positive electric field of ECP. Meanwhile, the gain effect of ECP also helped to promote the homogenization of molten steel.     

Geosynthetics for waterways and flood protection structures – Controlling the interaction of water and soil

The interaction of water and soil has been both a blessing and a curse in all times within living memory. Water is the origin of life but is also threatening life when appearing unboundedly. Therefore mankind has always worked hard to benefit from water resources on one hand and to deal with the threat of flooding on the other hand. For both, to protect the land and to allow for beneficial uses like irrigation or navigation, often special measures are necessary to keep the water within certain bounds. Structures to achieve a permanently stable situation like irrigation and navigational canals, river training or flood protection measures need suitable material, carefully thought out design and accurate execution. Often a decision has to be made among competitive approaches to optimize such structures. In many cases, geosynthetics can support or improve the functionality and sometimes only with geosynthetics the desired result can be achieved.     

Failure analysis on abnormal wall thinning of heat-transfer titanium tubes of condensers in nuclear power plant Part II: Erosion and cavitation corrosion

In Part I of the failure analysis on abnormal wall thinning of heat-transfer titanium tubes used in condensers in nuclear power plant, we analyzed the causes and mechanisms of abnormal thinning that commonly happened at the contact part between the tubes and the support plates. This kind of failure was the mainstream failure type in our case and the main causes were found to be eccentric contact wear and three-body contact wear rooted in processing defect of internal borings, corrosion products deposit and sagging, and foreign particles. However, there were still some individual failure tubes with different failure sites and modes and were located under the bypass pipes at the shoulder of the tube tower instead of in its lower part, obviously telling another failure story. In Part II of the failure analysis, material analysis, metallographic examination, mechanical performance tests, macro- and microstructure analysis and composition analysis were conducted. The failure causes were found to be erosion and cavitation corrosion and the synergetic effect of them. Finally, corresponding countermeasures were suggested.     

浅谈循环流化床锅炉水冷壁磨损问题

本文通过对一起锅炉检验中出现的缺陷现象,分析循环流化床锅炉水冷壁磨损方式及形成原因,并提出减轻磨损的方法。     

Manufacturing by combining Selective Laser Melting and Selective Laser Erosion/laser re-melting

This study presents an experimental investigation to improve Selective Laser Melting (SLM) regarding aspects such as surface roughness, density, precision and micro machining capability by employing secondary processes such as Selective Laser Erosion (SLE) and laser re-melting. SLM is a layered additive manufacturing technique for the direct fabrication of functional parts by fusing together metal powder particles. Laser re-melting, applied after each layer or only on the top surfaces, is used to improve the roughness and density while SLE, a subtractive process, is combined with SLM to improve the precision and micro machining capability.     

An experimental study of the relationship between settling flocs and eroded flocs of kaolinite in aqueous media

Aspects of the relationship between flocs in suspension and those held in a cohesive sediment bed were investigated experimentally using an erosion rig with kaolinite as the sample material under different medium conditions. The critical shear-stress, τ_c, required to initiate the erosion were measured, and the floc sizes of the eroded products (d_E) were analysed in situ using macro-photography. Factors such as age, density, pH and ionic strength were investigated. Separate experiments were performed to measure the floc size in the settling zone (d_A). The results show that the floc sizes from the above two different measurements show the same variance with respect to physico-chemical (pH and ionic strength) changes in the environment. This work has been very successful in showing the relationship between the flocs in suspension and those eroded from a bed of sediment, so one property can be predicted from knowledge of another.     

Erosion–corrosion of carbon steel in simulated tailing slurries

This paper investigates the synergism of mechanical and electrochemical factors in erosion–corrosion. The fact that active corrosion in the tailing slurry donates a small portion of total material loss indicates that the synergism results mainly from corrosion-enhanced erosion. As theoretically predicted, the erosion rates in corroding slurry under same hydrodynamic condition is a linear function of logarithmic corrosion rate, suggesting that the corrosion-induced surface plasticity is the dominate mechanism of corrosion-enhanced erosion. The reduced resistance to plastic deformation in surface layer while exposed to corroding media is demonstrated by the in situ micro-hardness measurements. The erosion-enhanced corrosion in flowing slurry of steel is a result of dynamic plastic deformation caused by erodent impingement.     

钛表面阳极化处理技术

通过对一台钛制设备阳极化处理工艺过程的详细介绍、氧化膜性能的考察及设备的跟踪调查,证明了阳极化处理后能提高钛制设备的硬度、耐磨性、耐蚀性和绝缘性。     

复合型气相防锈母粒的研制

介绍了气相防锈的原理和气相防锈塑料薄膜的性能特点着,重叙述了气相防锈母粒的配方设计和制造方法。     

Erosion–corrosion behaviour of Ni–20Cr plasma coating in actual boiler environment

Abstract

Erosion–corrosion is encountered in a large variety of engineering industries. In such environments, protective coatings are used. In this investigation, erosion–corrosion of the Ni–20Cr coating on nickel and iron based superalloys has been investigated by subjecting them to the boiler of coal fired thermal power plant at the temperature zone of 540°C for 1000 h duration. The erosion–corrosion kinetics of the plasma sprayed Ni–20Cr coating on different superalloys has been investigated. XRD, SEM with EDS and EPMA have been used to analyse the eroded–corroded products along the surface and cross-section. Main phases identified in all the Ni–20Cr coated superalloys after exposure are NiO, Cr₂O₃, Al₂O₃ and SiO₂. Aluminium has penetrated from the bond coat to the top coat along the splat boundaries. Oxides of chromium, nickel and aluminium are recognized as protective oxides for boiler environment. The probable mechanism of attack for Ni–20Cr coating in the given boiler environment is discussed.