L. Zheng, State University of New York at Stony Brook, Stony Brook, NY; W. Zhang, Edison Welding Institute, Columbus, OH; V. Srinivasan, Stony Brook University, Stony Brook, NY; S. Sampath, S.U.N.Y at Stony Brook, Stony Brook, NY
In this paper the influence of spray distance on the in-flight particle status has been investigated experimentally and numerically for Yttria Stabilized Zirconia (YSZ) and NiCrAlY thermal spray powders processed in an Ar-H2 plasma. Diagnostic tools such as IPP and SPT have been used to measure the plume characteristics and ensemble temperature, while DPV-2000 has been used to measure the distributions of individual particle characteristics such as temperature, velocity and size at the point of the maximum particle flux and other points (square grid) in the plume cross-section. By using a plasma spray 3D LAVA code, three-dimensional numerical simulations have been performed for the cases presented in the experiments accordingly. The in-flight particle characteristics and their distributions were studied at multiple spray distances to reveal the heating and melting mechanism for alloys and ceramics powders. Simulation results have been compared with experimental observations and very good agreement was achieved. For YSZ powder at certain stand-off distance, the particle velocity and temperature increase with spray distance and then decrease after reaching a maxima for a given process parameter combination; while for NiCrAlY powder, the particle velocity and temperature initially increase with spray distance and then fluctuate around the maximum value. For both YSZ and NiCrAlY powders, the mean particle size monotonically increases with spray distance. The resulting particle kinetic energy, melting index, and splat flattening ratio have been investigated. Also, the distributions of individual particle characteristics at various spray distances have been analyzed for both YSZ and NiCrAlY powders to understand their difference in melting and flattening status. This study can help to realize the spray distance optimization of air plasma spraying for both alloys and ceramics particles.
(I would like the paper to be considered for publication in a special issue of the Journal of Thermal Spray Technology as a peer-reviewed paper. Thanks!)
Summary: The influence of spray distance on the in-flight particle status has been investigated experimentally and numerically for Yttria Stabilized Zirconia (YSZ) and NiCrAlY thermal spray powders processed in an Ar-H2 plasma. Diagnostic tools such as IPP and SPT have been used to measure the plume characteristics and ensemble temperature, while DPV-2000 has been used to measure the distributions of individual particle characteristics such as temperature, velocity and size at the point of the maximum particle flux and other points (square grid) in the plume cross-section. By using a plasma spray 3D LAVA code, three-dimensional numerical simulations have been performed for the cases presented in the experiments accordingly. The in-flight particle characteristics and their distributions were studied at multiple spray distances to reveal the heating and melting mechanism for alloys and ceramics powders.
