iTSSe TSS 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 | A P R I L 2 0 2 1 4 3 iTSSe TSS 10 that are expected for aerospace gas turbine engines by the employment of ceramic matrix composites (CMCs) and thermally sprayed environmental barrier coatings (EBCs) in their hot zones (e.g., combustion chambers, vanes, shrouds, blades, and afterburners). Among these achievements, those typically highlighted are: (i) turbine weight reduction, (ii) reduced fuel consumption, (iii) higher operation temperatures, (iv) superior thrust-to-weight ratio, and (v) lower emission of toxic gases to the atmosphere. The objective of this tutorial paper is to present to the reader how these feats are achieved by the concomitant combination of imaginative engineering. It will explain the non-stop driving force for increasing combustion temperatures; show the basic concepts of CMCs, the paramount need of EBCs, and the complexity of creating EBC architectures via air plasma spray (APS). Finally, highlights on how EBCs/CMCs are tested at high temperature will be provided. (Fig. 3) In this work, high rate deposition of tantalum was studied computationally and experimentally. Quasi-1D multiphase fluid simulations predicted minimal effects on the bonding conditions of particles with 5% to 14% increase in powder-togas mass flow ratio. Experimental specimens were produced to observe the mechanical and microstructural effects of increased powder stream loading. Adhesion and hardness tests as well as thermal conductivity, optical microscopy, and electronbackscatter diffraction examinations only exhibitedminor differences in the mechanical and microstructural properties of the specimens. (Fig. 4) BONDING MECHANISMS IN COLD SPRAY: INFLUENCE OF SURFACE OXIDATION DURING POWDER STORAGE MaryamRazavipour, Saeed Rahmati, Alejandro Zúñiga, Denise Criado, and Bertrand Jodoin Cold spray is a solid-state process in which solid particles are subjected to severe plastic deformation to form a coating. The effect of naturally occurring oxides on bonding in the cold spray was investigated in this work. Deposition characteristics of copper powder with different surface oxide thicknesses on steel substrate were examined using a local pull-off test. This enables the investigation of individual particle/substrate interfaces. X-ray photoelectron spectroscopy was used to study thoroughly the powder surface chemistry and the oxide thickness as a function of exposure time. (Fig. 5) Fig. 4 — EBSD Euler orientation maps for coatings deposited at (a) 5.0%, (b) 8.4% particle loading rates. Black pixels indicate unindexed locations or high angle grain boundaries (>10°). Arrows identify representative lenticular grains. Fig. 3 — SEM picture of a polished cross-section of a CMC. HIGH RATE DEPOSITION IN COLD SPRAY Ozan C. Ozdemir, Patricia Schwartz, Sinan Muftu, Forest C. Thompson, Grant A. Crawford, Aaron T. Nardi, Victor K. Champagne, Jr., and Christian A. Widener Industrialization of cold spray introduces concerns regarding the cost and time efficiency of cold spray procedures. Fig. 5 — Cross-section SEM images of as-received copper powder (a) before etching and (b) after etching. 11 JTST HIGHLIGHTS
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