Abstract

The thermal spray process involves the injection of particulates into a high flux environment so that momentum and heat transfer can take place. The particles are then accelerated within the gaseous effluent and within several milliseconds impact and splash against a suitably prepared substrate. In this fashion a coating rapidly grows over a time period that may range from minutes to hours.

The materials engineering concept comes into play when it is appreciated that the temperature, velocity, and chemical nature of the spray effluent controls the dispersion, impact phenomenon, and, therefore, the precise nature of the microstructure which is being formed in situ and in real time. Unsurprisingly, this is a somewhat random and chaotic process that is seeking practical and theoretical solutions so that some manner of engineering control can be employed.

This paper explores the scientific relationship between materials engineers and mechanical engineers so that a functional product can evolve. This relationship includes (i) the use of diagnostic equipment to monitor the spray process, (ii) the dynamic impact behavior of particulates, (iii) modeling of thermal fluxes and the resultant mechanical stress state, and (iv) the way in which the microstructure evolves. The eventual aim of this vast body of work is to enable real time feedback loops for the thermal spray process so that predictable and engineered structures can be manufactured.

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