This Small Business Technology Transfer (STTR) Phase I project will develop prototypes of two novel, fast deposition rate sensors that will enable implementation of real-time deposition rate control for plasma spray. Plasma spray is currently run open loop with respect to the actual particle states and is characterized by large variations which affect yield and quality. Preliminary research reveals that currently available sensors, which measure average particle temperature and velocity, are not well correlated to deposition rate. The new sensor concepts measure particle flux using a high speed CCD array and molten flux using spectral deconvolution, both of which have been shown to correlate well to deposition rate. These new high speed sensors will provide the basis for implementing real time control that can significantly reduce coating thickness variation, a primary plasma spray performance metric.
Plasma spray is a high-throughput, economical, low environmental impact process that can be used to custom engineer coating microstructure to meet specific performance requirements. It is used extensively to coat turbine components with thermal barrier coatings (world wide market of $2.5 B where US has a 35% market share) as well as emerging applications such as the electrolyte coating for fuel cells. The sensor technology proposed in this project, enabling real-time control, will enhance the process capability of plasma spray to achieve greater than 2 sigma capability, enhancing coating quality, reliability and relieving some of the cost pressures faced by domestic manufacturers.
