Scale-up design for industrial development of a PP-MOCVD coating system

The scale-up of research results into industrial processes is a challenge for CVD commercialization. Pulsed-pressure metal-organic (PP-MOCVD) technology does not use a carrier gas. A low-concentration precursor liquid solution is injected into the deposition chamber in discreet, timed pulses. Previous research has indicated that three-dimensional, complex-shaped objects could be coated, and that the process could be scaled-up using simple geometric and time constant relations. This research presents the scale-up design process for a machine to coat a particular product, a stainless steel water pump impeller. Design relations to avoid choked flow and produce uniform coating thickness at high growth rate were estimated and verified experimentally. The pump was inductively heated to 450°C and coated with TiO₂ from alkoxide precursor. The coating had good coverage and was estimated to be 5-6μm thick.