Conceptual design of a low pressure cold gas dynamic spray (LPCGDS) system

Abstract

Low Pressure Cold Gas Dynamic Spray (LPCGDS) is a coating process that utilises kinetic energy instead of thermal energy to deposit powder particles (1-50 μm) to substrates at low temperatures (<400 oC) without going through melting. The deposited coatings provide improved wear and corrosion protection to underlying surfaces while maintaining the original phase structure of the particles and minimising oxide formation and residual stresses associated with conventional thermal spray processes such as flame, arc and plasma spraying. Bonding occurs when particles impact velocities on the substrates exceed a certain critical velocity. This critical velocity depends on the propellant gas and particles characteristics, and the spray system components (gas supply, gas heater, powder feeder and the supersonic nozzle) design. Consequently, design optimisation of these parameters is a key to improve the coating quality and reduce the spraying costs. This study develops an effective and efficient conceptual design of a LPCGDS system. Requirements for both the overall LPCGDS system and its individual components or subsystems are established. Components variants that include off-the-shelf, customised and innovative solutions are generated. An evaluation of these variants is then carried out to determine components that best performs LPCGDS functions. Subsequently, an optimal spray system that meets the specifications of the LPCGDS system is assembled from these best components. Finally, a complete spray set-up that includes the spraying chamber, a gas and particle recovery system, the data acquisition and control system and, coating quality measurement equipment is established.