Effect of Substrate and Its Shape on in-Flight Particle Characteristics in Suspension Plasma Spraying
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JTTEE5 25:44–54 DOI: 10.1007/s11666-015-0342-z 1059-9630/$19.00 ASM International
Effect of Substrate and Its Shape on in-Flight Particle Characteristics in Suspension Plasma Spraying K. Pourang, C. Moreau, and A. Dolatabadi (Submitted June 14, 2015; in revised form October 6, 2015) Obtaining a uniform coating on curved mechanical parts such as gas turbine blades is one of the industrial challenges in suspension plasma spraying. Through a three dimensional numerical analysis, this study is aimed at providing a better understanding of the effect of substrate curvature on in-flight particle temperature, velocity, and trajectory. The high temperature and high velocity plasma flow is simulated inside the plasma torch using a uniform volumetric heat source in the energy equation. The suspension of yttria-stabilized zirconia particles is molded as a multicomponent droplet while catastrophic breakup regime is considered for simulating the secondary break up when the suspension interacts with the plasma flow. A two-way coupled Eulerian-Lagrangian approach along with a stochastic discrete model was used to track the particle trajectory. Particle size distribution in the vicinity of the substrate at different stand-off distances has been investigated. The results show that sub-micron particles obtain higher velocity and temperature compared to the larger particles. However, due to the small Stokes number associated with sub-micron particles, they are more sensitive to the change of the gas flow streamlines in the vicinity of a curved substrate.
Keywords
deposition rate, droplet breakup, particle trajectory, suspension plasma spray
1. Introduction In the recent decades, producing nano-structured coatings has been one of the major interesting research subjects due to their notable properties such as better dimensional stability or lower thermal diffusivity compared to conventional ones (Ref 1). One of the challenges in this area was finding a way to inject these nano-sized particles into the gas flow. To address this problem, a new technique called suspension plasma spraying (SPS) is being used. In this technique, suspension of nano-or submicron-sized particles in a base fluid (usually ethanol or water) is injected into the plasma plume in a form of liquid jet or train of fragmented droplets (Ref 2). The use of liquid carrier is to provide the required momentum for the small-sized particles to penetrate inside the plasma. However, transport of suspension into plasma flow is a complex phenomenon and there are various parameters This article is an invited paper selected from presentations at the 2015 International Thermal Spray Conference, held May 11–14, 2015, in Long Beach, California, USA, and has been expanded from the original presentation. K. Pourang, C. Moreau, and A. Dolatabadi, Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QCCanada. Contact e-mail: ali.dolatabadi@ concordia.ca.
44—Volume 25(1-2) January 2016
that affect the properties of the SPS coatings such as torch opera
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