This paper describes the basic design and operation of a low-pressure plasma spraying (LPPS) system in use at Sandia National Laboratories. To demonstrate the versatility of the system, Sandia engineers, working in collaboration with the New Mexico Institute of Mining and Technology, produced thin (< 100 μm), dense yttria-stabilized zirconia coatings using three deposition mechanisms: liquid droplet, vapor, and mixed mode (vapor and droplet). Despite slight differences in equipment configuration, the work duplicates many of the results obtained in previous investigations, confirming the advantages of LPPS over other thin film deposition techniques.

Use of graded coatings is a well-known strategy for creating materials with continuously changing physical properties. The stiffness (modulus of elasticity) and density of flyer plates used in light gas gun testing directly influences the shape of the shock wave produced by the flyer plate. Many strategies exist for creating flyer plates that produce variable shock profiles, including stacked foils and powder compaction. We have investigated graded thermal spray coatings as an alternative method for creating flyer plates that produce variable shock profiles. An initial proof of concept demonstration has been completed by air plasma spraying a graded coating of Cu & Al onto a copper substrate. This composite flyer plate was tested in a light gas gun to demonstrate that a non-linear shock profile can be created. The plasma spray strategies used to create a group of similar graded density impactors are discussed. Initial light gas gun testing shows that graded density impactors can be created using thermal spray coatings.

The effect of torch hardware, operating parameters, and powder type on substrate surface heat flux was quantitatively investigated using calorimeters. The Sulzer-Metco 6P oxyacetylene torch with two nozzles and two air caps and the Alamo PG-550 torch were studied using designed experiments to show the effects of total combustible gas flow, oxy-fuel ratio, air flow, and standoff distance on surface heat flux. Air caps which directed cooling air toward the flame produced lower heat flux than air caps providing gun cooling. For the 6P torch, nozzle geometry did not have a significant effect on heat flux. With low air flow rates, both torches exhibited similar heat fluxes. At high air flows, the surface heat flux of the PG-550 was larger than that of the 6P.

The effect of hardware on operating parameters and the resultant coating are qualitatively known; however, the quantitative effects have not been well defined. This study quantitatively characterizes particle temperature and velocity for the Sulzer-Metco 6P oxy-acetylene torch with 3 different nozzles and 3 air caps and also, the Alamo PG-550 then relates those data to particle diagnostics, deposition efficiency and coating microstructure. Both torches were evaluated using statistically designed experiments where the process inputs of oxy-fuel ratio, total combustible gas flow, and standoff distance were varied. Both torches can access similar regions of particle temperature - particle velocity space. Increasing total combustible gas flow increased particle velocity with little effect on particle temperature. Increasing oxy-fuel ratio decreased particle temperature with little effect on particle velocity. Higher particle velocity and particle temperature conditions yielded denser, less porous coatings. Flame cooling air caps increase the particle speed while decreasing particle temperature. Nozzles which inject powder directly into the flame jets significantly increase particle temperature as compared to nozzles which do not. Deposition efficiency is shown to not only be affected by particle temperature and particle velocity where hotter and faster usually increase efficiency, but is also dependent on the distribution of particles within the plume.

Cold spray is adding another dimension to thermal spray coating processes with numerous applications that have yet to be realized. Current activities in the field of Cold Spray are rapidly moving from R&D to commercial applications in industry. To successfully commercialize the technology, cost effective, low maintenance, highly reliable, easy to operate equipment must be available and supported that is designed so that the spray processes can be controlled and repeated. With the growth of this technology there will be a demand for laboratory systems to perform applications research and development as well as high volume production machines for specific industrial applications. The recent focus of Cold Spray equipment development has been to perfect nozzles and gun assemblies, gas heaters, gas flow, powder feed, and process control. This paper describes the automated equipment that is available in the market today and presents advances in nozzle and gas heater performance as well as development of a laboratory powder feeder. This equipment will serve as the baseline for equipment that will soon be installed in industry for commercial production applications.

Cold Spray is a rapidly emerging technology with numerous applications that have not yet been realized. With the growth of this technology there will be a demand for laboratory systems to perform applications research and development as well as high volume production machines for specific industrial applications. The recent focus of Cold Spray equipment development has been to perfect nozzles and gun assemblies, gas heaters, gas flow, powder feed, and process control. This paper describes the automated equipment that is available in the market and presents some performance data. This equipment will serve as the prototype for the industrial equipment that will soon be designed and installed in industry for commercial production applications.

The rapid emergence of cold spray technology provides numerous applications that require spraying fine (<10 microns) powders, providing more uniform deposition, improved measurement of deposition efficiency and quick turn around time. The performance of high-pressure commercial powder feeders, currently available, lacks one or more of these desired performance characteristics. Further, researchers are interested in spraying many powders of different materials or particle size distributions where the powder feeder can be quickly and easily cleaned without replacing expensive consumables. The Ktech laboratory powder feeder has been designed to operate under a wide variety of carrier gas pressures (0 – 500 psig). This laboratory feeder delivers a continuous flow of powder, has a variable canister volume and is quick and easy to clean. This unique design facilitates short run research applications or higher volume extended run time dispensing. The feeder is designed to operate in either a locally or remotely through a PC based Ethernet connection. The laboratory powder feeder represents an excellent tool for high-pressure cold spray or low-pressure thermal spray processes requiring the delivery of fine powders.