The distributions of spray particle velocity and temperature were determined with two different instruments, the SpectraViz (Stratonics, Laguna Hills, CA) and the DPV2000 (Tecnar Automation, Montreal, Canada). Experiments were performed with three different powders and a Praxair SG 100 plasma spray torch. The instruments differ by the method they use in imaging the jet ultimately allowing for measurements of velocities and temperatures. The average particle temperature values obtained are very close, indicating that different ways of imaging do not influence the measurement value. The values for the average velocities are in good agreement for two of the powders tested (Al 2 O 3 and CrO 2 ), however, for the YSZ powder a consistent difference in velocity values was found. It appears that for obtaining average values e.g. for process control, both instruments are equivalent.

Wire arc spray is a process for producing coatings and forming structures through the deposition of metal droplets. Wire arc spray has the advantage of low material coast and low power requirements when compared to other thermal spray technologies. This article elaborates on the assumptions made for using single consumable wire geometry, discusses experiments performed to test these assumptions, presents droplet generation results, and addresses required future work. Experiments revealed a critical relationship between wire polarity, wire position, and droplet beam dispersion. The article identifies a critical relationship between wire polarity, wire position, and spray pattern divergence in a single wire arc spray device.

This paper aims to achieve improved control over the spray pattern in a wire arc torch by means of constructive measures to influence the flow dynamics. It focuses on evaluating different fluid dynamic designs of the spray torches with respect to the droplet trajectories and velocity distributions and the deposit distribution. First, the paper describes the approaches for novel nozzle designs including the addition of shrouds and the torch evaluation diagnostics, and then presents the results for four different nozzle arrangements. It is observed that the nozzle design and the placement of the wire tips within the nozzle have the greatest effect on the divergence of the spray pattern. Paper includes a German-language abstract.

There is widespread industrial interest in wire arc spraying as it has proven to be a relatively inexpensive alternative providing high quality coatings in many applications. Modeling and experimental studies have been conducted with different nozzle geometries to study the influence of fluid dynamics on the behavior of the particles which form the coating. Schlieren optical diagnostics and image analysis are used to study flow patterns obtained with different nozzle geometries. Supplementary measurements are made with static and total pressure probes. A particle breakup model is used to predict the trajectory and breakup of molten particles in the jet. This investigation indicates that nozzle designs that minimize or eliminate shock formation before the atomizing gas reaches the wire tips result in lower coating porosity and a more uniform particle size distribution.