Pressure-Based Liquid Feed System for Suspension Plasma Spray Coatings

Abstract

Thermal spraying with liquid-based feedstocks demonstrated a potential to produce coatings with new and enhanced characteristics. A liquid delivery system prototype was developed and tested in this study. The feeder is based on the 5MPE platform and uses a pressure setup to optimally inject and atomize liquid feedstock into a plasma plume. A novel self-cleaning apparatus is incorporated into the system to greatly reduce problems associated with clogging and agglomeration of liquid suspensions. This approach also allows the liquid feedstock line to the gun to remain charged for quick on-off operation. Experiments on aqueous and ethanol-based suspensions of titania, alumina, and YSZ were performed through this liquid delivery system using a 9MB plasma gun. Coatings with ultrafine splat microstructures were obtained by plasma spraying of those suspensions. Phase composition and microstructure of the as-sprayed coatings were investigated.

Demands, Potentials, and Economic Aspects of Thermal Spraying with Suspensions: A Critical Review

“…Technological development of spraying with suspensions has thus far been concentrated in research institutions using laboratory-scale set-up integrated into the current spray booths. Intense efforts have been made in industry recently to develop suspension feeder hardware components, especially suspension feeders, as evidenced by the patent literature (i.e., Ref 24,25). However, information on industrial activities in conference proceedings and journal articles is relatively scarce up to now (e.g., Ref 26 (Fig.…”

Status and future trends in suspension spray techniques

“…Two examples of commercially available systems are given in Figure 4.10a and b (refer to Cotler et al, 2011). Both concepts have their own benefits and drawbacks.…”

“…10 Suspension feeder concepts: (a) NanoFeed from Northwest Mettech Corp., Vancouver, Canada; (b) pressurized feeder prototype from Sulzer AG, Wohlen, Switzerland(Cotler et al, 2011). With permission from the manufacturers.…”

Suspension plasma sprayed coatings using dilute hydrothermally produced titania feedstocks for photocatalytic applications

“…Feeding powders in this way has inherent problems as all powders have to be carefully selected to have the right ow properties so that they can be fed without blockages, which requires additional effort (sieving) and limits the range of usable particle sizes. 16 Using suspension thermal spraying, high quality coatings have reportedly been achieved by the use of commercial titanium dioxide nanopowder suspensions rather than a dry thermal spray powder feed, via suspension plasma spraying (SPS). [17][18][19] In this process, a suspension of titania is fed into a plasma jet, which evaporates the liquid causing the material to agglomerate, and can melt the particles while accelerating them onto a substrate where they impact to form a coating.…”

“…Unstable suspensions undergo agglomeration and settling, which can result in blockage of lines and injectors. 16 Suspension spray is a relatively new technology and commercially available suspensions are sparse. Typically, published work on suspension spray of titania, whether via high velocity suspension ame spraying (HVSFS) or SPS, has been conducted using suspensions of ca.…”