(Color online) Schematic illustration of a directed vapor deposition process showing the electron beam evaporated vapor plume and model airfoil sample geometry. A mixture of 90% He and 10% O2 was used for experimental studies.
(Color online) Geometry, dimensions, and coordinate system of the model airfoil and substrate to which it was attached.
(Color online) Schematic of DSMC simulation mesh containing 17 217 cells. The cells immediately above the (green) vapor source have lengths of 2.52 μm.
(Color online) Contour plots of Zr vapor atom concentration for a chamber pressure of 16 Pa and three nozzle pressure ratios: (a) 2.0, (b) 4.5, and (c) 7.5.
(Color online) Contour plots of Zr concentration at a nozzle pressure ratio of 2.0 and chamber pressures of (a) 16 Pa, (b) 30 Pa, and (c) 45 Pa.
(Color online) He streamlines and pressure contours near the substrate at a chamber pressure of 16 Pa and nozzle pressure ratio of 2.0.
Schematic illustration demonstrating the paths of vapor atoms that deposit on the concave surface, leading edge, and convex surface. The random walk path of a hypothetical individual atom is overlaid with the average trajectory of vapor atoms in the region.
Zr vapor atom streamlines for at a fixed chamber pressure and pressure ratios of (a) 2.0, (b) 4.5, and (c) 7.0. The vapor atom capture distance is noted on each flow field. The capture distance decreases with increasing pressure ratio (jet speed), resulting in a reduction of deposited flux onto the substrate surface.
Zr vapor atom streamlines at a fixed pressure ratio of 2.0 and chamber pressures of (a) 7.5 Pa, (b) 30 Pa, and (c) 45 Pa. The capture distance decreases with increasing chamber pressure.
(Color online) Flux profiles along the (a) concave and (b) convex airfoil surfaces at a fixed chamber pressure of 16 Pa and varying pressure ratio. Regions on the substrate not within the line-of-sight of the vapor source are indicated on the plots as “NLS Region.”
(Color online) Flux profiles along the (a) concave and (b) convex airfoil surfaces for a pressure ratio of 2.0 and varying chamber pressures.
Comparison of experimental and simulated thickness profiles along (a) concave and (b) convex surfaces. The experiment and simulation were both conducted at a chamber pressure of 16 Pa and pressure ratio of 3.5.
SEM images of the coating at various locations on the airfoil substrate with the average columnar growth angle indicated. Note the differences in magnification between images.
Incident angle distribution at the six substrate surface locations defined in Fig. 12 for a simulation at 16 Pa and pressure ratio of 3.5. The IAD is defined with the local surface normal at θ = 0 as shown at the top of the figure.
(Color online) IAD at center of concave surface (location e in Fig. 15 ) showing the effects of varying (a) the nozzle pressure ratio and (b) the chamber pressure. The result for a conventional (low pressure) PVD simulation is also shown on (b).
Comparison of PVD and DVD flux profiles along (a) concave and (b) convex substrate surfaces. The DVD simulation was conducted at a chamber pressure of 16 Pa and pressure ratio of 2.0. The PVD simulation was conducted at a chamber pressure of 0.02 Pa.
He jet velocities upstream and downstream of the substrate with various pressure ratios. The velocity at both locations increases with increased pressure ratios.
He jet velocities upstream and downstream of the substrate at various chamber pressures. The velocity decreases with increasing chamber pressure.
Comparison of columnar growth angles predicted by the Tangent rule, and measured from experiments.
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