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

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JTST HiGHliGHTs high temperatures in contrast to YSZ. Mg-Al-spinel deposition by SPS results in columnar-structured coatings, which were tested for their thermal cycling lifetime. The influence of substrate cooling during the spray process on thermal cy- cling behavior, phase composition, and stoichiometry of Mg-Al-spinel was also investigated. "Tailoring the spray Conditions for suspension plasma spraying" A. Joulia, w. Duarte, s. Goutier, m. Vardelle, A. Vardelle, and s. Rossignol Plasma spray using suspensions as liquid feedstock al- lows deposition of finely structured coatings with improved properties compared to that of coatings deposited by con- ventional plasma spray techniques. The evaporation of the solvent, acceleration, heating, and melting of fine solid par- ticles within the plasma jet take place in a shorter time, as the substrate is located closer to the plasma torch when a mono-cathode mono-anode plasma torch is used, while liquid material processing globally consumes more energy than powder materials. In this study, a large range of plasma spray conditions were used to achieve yttria-stabilized zir- conia coatings by suspension plasma spray. The properties of the plasma jet (velocity, enthalpy, and stability) as well as those of droplets (trajectories, num- ber, and size) and particles (velocity) were measured and correlated to the coating microstruc- ture. The operating conditions neces- sary for obtaining disk-shape splats and achieving ho- mogeneous coatings are described including plasma jet properties and substrate parameters. "interface Characterization and bonding mechanisms of Cold Gas-sprayed Al Coatings on Ceramic substrates" R. Drehmann, T. Grund, T. lampke, b. wielage, k. manygoats, T. schucknecht, and D. Rafaja Research aims to contribute to the understanding of adhesion mechanisms, which take effect at the interface of cold gas-sprayed metallic coatings on ceramic substrates. Former investigations reveal the possibility to deposit well-adhering metallic coatings on atomically smooth ce- ramics, meaning that mechanical interlocking is not al- ways a necessary precondition for bonding. A combination of recrystallization processes induced by adiabatic shear processes and heteroepitaxial growth might explain high observed adhesion strengths. The present work examines the interface area of cold gas-sprayed aluminum on various ceramic substrates using SEM and HRTEM. Besides sintered corundum plates, single-crystalline sapphire substrates with defined lattice orientations were used as substrates for coating deposition. In addition to Al2O3 substrates, alumi- num coatings were also deposited on AlN, Si3N4, and SiC to investigate whether different amounts of ionic bonds in these substrate materials influence the substrate/coating interface formation. Interface of (0001)-oriented sapphire with (111)-oriented PVD Al coating (TEM image). Directions normal to the lattice planes (determined by XRD pole figures) are indicated by arrows. SEM micrograph of YSZ splats collected at 30 mm from nozzle exit. Arc current: 600 A. Plasma gas composition: Ar (77%)-He (33%). Substrate: 400°C. i T S S e | 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 1 6 iTSSe | TSS

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