The emphasis in this Thrust Area is on establishing and broadening the

science and technology bases for high rate, economical coating processes,

including plasma spraying, wire arc spraying and thermal plasma chemical

vapor deposition (TPCVD). A combination of advanced diagnostics and

modeling is used to enhance our understanding of the fundamentals of the

interactions between plasmas and particles or liquid droplets and chemical

precursors for the coatings. This understanding then provides the

guidelines for developing new equipment and process designs, such as

nozzles and shrouds to modify the fluid dynamics, and for developing

sensors and control strategies for advanced process controls. These

activities will lead to improved process tolerance against the influences

of uncontrolled parameters.

Specific activities which are presently being pursued are:

A) Plasma spraying:

* Nozzle and shroud development and evaluation for increased plasma jet

stability, and improved deposition efficiency and consistency of coating

quality.

* Development of sensors and control algorithms for detecting and avoiding

variations in plasma jet behavior and coating quality.

B) Wire arc spraying:

* Spray pattern control through different nozzle and shroud designs.

* Development of fundamental process correlations using process models and

advanced diagnostics with a novel torch.

* Application of novel control algorithm based on computer analysis of arc

voltage traces.

C) Thermal plasma CVD:

* Texture control during high rate diamond film deposition through

detailed understanding of the boundary layer chemistry based on modeling

and diagnostics using gas chromatography.

* Arcjet deposition at high rates of hard, boron containing films.

There are several complementary projects spanning a wide spectrum from

fundamental studies in arc technologies, electrode attachment control and

plasma heat transfer to specific industrial applications.

Recent collaborations with industrial partners:

* Plasma spray model for process control development.

* High definition arc spray system development.

* Torch cathode erosion mechanism investigation.

* Barrier discharge characterization.

Collaborations with other laboratories:

Stanford University High Temperature Gas Dynamics Laboratory; SUNY Stony

Brook Thermal Spray Laboratory, University of Limoges, France: Technical

University of Ilmenau, Germany; University of Tokyo, Japan; University of

Sherbrooke, Canada.

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