Advanced Materials & Processes

FEB 2015

Covers developments in engineering materials selection, processing, fabrication, testing/characterization, materials engineering trends, and emerging technologies, industrial and consumer applications, as well as business and management trends

Issue link: http://amp.digitaledition.asminternational.org/i/466012

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JTST HiGHliGHTs The Journal of Thermal Spray Technolo- gy (JTST), the official journal of the ASM Thermal Spray Society, publishes con- tributions on all aspects—fundamental and practical—of thermal spray science, including processes, feedstock manu- facture, testing, and characterization. As the primary vehicle for thermal spray information transfer, its mission is to syn- ergize the rapidly advancing thermal spray industry and relat- ed industries by presenting research and development efforts leading to advancements in implementable engineering appli- cations of the technology. Articles from the January issue, as selected by JTST Editor-in-Chief Christian Moreau and Lead Ed- itor Armelle Vardelle, are highlighted here. This issue features papers based on presentations at ITSC 2014. In addition to the print publication, JTST is available online through springerlink. com. For more information, visit asminternational.org/tss. "Thermal spray Coatings for High-Temperature Corrosion protection in biomass Co-Fired boilers" m. oksa, J. metsäjoki, and J. kärki There are over 1000 biomass boilers and roughly 500 plants us- ing waste as fuel in Europe, and numbers are increasing. Many encounter serious problems with high-temperature corrosion due to detrimental elements such as chlorides, alkali metals, and heavy metals. HVOF spray produces very dense and well-adhered coatings, which can be applied for corro- sion protection of heat exchanger surfaces in biomass and waste-to-energy power plant boilers. Four HVOF coatings and one arc sprayed coating were exposed to actual biomass co-fired boiler conditions in a superheater area with a probe measurement installation for 5900 h at 550° and 750°C. Coating materials include Ni-Cr, IN625, Fe-Cr-W-Nb- Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for HVOF spray to compare the corrosion resistance of Ni-Cr coat- ing structures. Reference materials were ferritic steel T92 and nickel super alloy A263. The circulating fluidized bed boiler burnt a mixture of wood, peat, and coal. Coatings show excel- lent corrosion resistance at 550°C compared to ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during exposure at 750°C. "in situ wear Test on Thermal spray Coatings in a large Chamber scanning Electron microscope" weifeng luo, wolfgang Tillmann, and ursula selvadurai Currently, mass loss determination is usually used for quantitative evaluation of wear tests, while analysis of wear tracks is used for qual- itative evaluation. Both eval- uation methods can only be used after wear testing and results can only be present- ed in the final outcome of wear tests. However, chang- es during the wear test and time-dependent wear mechanisms are also of great interest. A running wear test in a large chamber scanning electron microscope (SEM) offers the first opportunity to observe the wear process in situ. Different wear mechanisms, such as the adhesive, abrasive wear, surface fatigue, and tribochemical reaction, can be recorded with high magnification. A special pin-on-disk testing device was designed for a vacuum envi- ronment. Using this device, arc-sprayed NiCrBSi coatings and HVOF-sprayed WC-12Co coatings were tested in a large cham- ber SEM with Al2O3 ceramic balls as wear counterparts. During wear testing, different wear mechanisms were determined and processes were recorded in short video streams. "Columnar-structured mg-Al-spinel Thermal barrier Coatings (TbCs) by suspension plasma spraying (sps)" n. schlegel, s. Ebert, G. mauer, and R. Vaßen Suspension plasma spray (SPS) was developed to per- mit feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposi- tion and plasma spray-physical vapor deposition, SPS enables cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an import- ant role in the field of thermal barrier coatings (TBCs). Yttria partially stabilized zirconia (YSZ) is commonly used as TBC material. However, its long-term application at temperatures higher than 1200°C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits, Mg-Al-spi- nel was used as a TBC material. Even though it has a lower melting point (~2135°C) and higher thermal con - ductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at Schematic representation of the surface fatigue around a pit on a coating's surface. Suspension-feeder developed at Forschungszentrum Jülich GmbH (Germany), showing the monitoring and control unit (a), and injection of suspension into the plasma jet with a two- phase atomizer (b). 550 MWth circulating fluidized bed boiler test facility with the probe measurement location. a d v a n c e d m a t e r i a l s & p r o c e s s e s | F e B r U a r Y 2 0 1 5 | i T S S e 1 5 iTSSe | TSS

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