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.

Modification of the nozzle of the arc spray equipment was attempted in order to reduce microstructural defects of the spray-formed steel shells since these defects mainly degrade the overall properties of the spray-formed tools. Based on the in-flight particle analysis, a new nozzle design of a gas shrouding concept was proposed. Effects of design factors such as nozzle dimensions and process conditions was investigated by using statistical analysis methods. The results demonstrated that the oxidation of the spray-formed steel shells can be reduced to the one-third levels of the original ones with an optimized design.

This paper presents the results of research on novel methods for the manufacturing of metallic gas flow, bi polar plates (BPP) for use in proton exchange membrane fuel cells (PEMFC). Low cost, high speed, additive manufacturing methods that combine thermal spray (TS) and 3D printing (3DP) technologies are described. Flow plates were manufactured by creating 3DP patterns then depositing material with TS, and finally releasing the newly formed part. This net-shape spray forming method yields dense metal plates with interesting options for material choices and complex designs.

Functionally graded material (FGM) designs aim to combat challenges posed by harsh and conflicting operational requirements. There is a great demand for manufacturing technologies that can fabricate net-shape components incorporating the FGM design concepts. The focus of this paper is on the development of net-shape components incorporating functionally gradient material designs. This novel manufacturing scheme combines the use of re-useable mandrels to generate complex shapes with a unique thermal spray process called “hybrid spray” that can deposit functionally designed materials. This generic hybrid spray process combines arc spraying with either high velocity oxy-fuel (HVOF) or plasma spraying (APS). The resulting benefits are; ability to achieve continuous composition variation, high deposition rates combined with the high coating densities. The multi-material component designs aim to provide cost as well as performance advantages. The geometric resolution and dimensional accuracy of these functional components are presented. This paper also reports results on material compatibility and process parameter development tests. Functional properties such as high temperature resistance and thermal fatigue performance are also reported.

Plasma spray forming ceramic components on a mandrel provides a way of net shape forming of difficult to machine materials. In addition, the structure of plasma sprayed ceramics contains fine porosity that improves strain accommodation as compared to sintered ceramics. However, plasma spray forming causes complex stress states in materials that may lead to cracking during spraying or during separation from the mandrel. Monitoring surface temperatures by infrared videography and controlling deposit surface temperature by directed cooling can be used to minimize thermal gradients and minimize part cracking. Control of thermal stresses is also necessary for proper separation of the sprayed part from the mandrel. Details of the plasma spray forming of yttrium oxide crucibles show how temperature monitoring, directed cooling, and robot manipulation are used to produce a crack free crucible.

In this paper the principle of “Thermal Spray Molding” and some application are presented. Micro technology is a very fast growing market nowadays. Metallic micro devices can be produced for example by means of stereo lithography and selective etching. Unfortunately the material range for these processes is limited. The new manufacturing concept of thermal spray molding uses powder or wire as base material, so that an extended material choice for micro parts, for example micro components made of super hard or corrosion resistant steel is possible.