As the initial step of a process control design for a substrate surface temperature control solution for Vacuum Plasma Spraying (VPS), the distribution of heat transfer coefficient h between impinging plasma gases and the substrate coating surface is required. An embedded calorimeter approach was used to measure the distribution of the convective heat transfer coefficient over the surface of a substrate and the resulting distributions have been compared with empirical correlations and CFD model predictions of the plasma jet/substrate interaction, as a function of VPS process parameters.

For the last seven years, Oxford University and the Ford Motor Co. have been researching jointly the development of the large-scale spray forming of steel tooling capable for use in mass production, particularly for the pressing of sheet metal in automotive applications. These investigations have involved: comprehensive microstructure and property studies, modelling of shape evolution and heat flow, real-time feedback control of tool temperature to eliminate tool distortion, high speed imaging and particle image velocimetry of droplet deposition on 3D shapes, the testing of full-scale tools for different applications in the production environment, and detailed studies of the cost and time savings realised for different tooling applications. This paper will provide an overview of the scientific and technical progress to date, present latest results, and describe the current state-of-the-art. Many of the insights described have relevance and applicability across the family of thermal spray processes and applications.