The exceptional properties of beryllium (Be) including low density and high elastic modulus, make it the material of choice in many defense and aerospace applications. However, health hazards associated with Be material handling limit the applications that are suited for its use. Innovative solutions that enable continued use of Be in critical applications while addressing worker health concerns are highly desirable. Plasma Transferred Arc solid freeform fabrication is being evaluated as a Be fabrication technique for civilian and military space based components. Initial experiments producing beryllium deposits are reported here. Deposit shape, microstructure and mechanical properties are 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.

Transferred-arc cleaning and roughening as discussed in the patent by Muhlberger is often used as a surface preparation method prior to low pressure plasma spray (LPPS) deposition of coatings. In this article, electrically transmitted arc cleaning is investigated as a precision cleaning method for thin films lubricating substrates as well as traditional cleaning and roughening for LPPS. A Box-Behnken reaction surface construction test is carried out with variation of the chamber pressure, the substrate distance and the torch current taking into account the transferred arc voltage, the voltage fluctuation, the current, the emitted light, and the surface cleanliness. The results of the analysis show the effect of the various independent quantities on the measured responses. Different stages in the cleaning process are determined by their sample cleanliness, their voltage level, their voltage fluctuation, their emitted light and their rate of erosion. Paper includes a German-language abstract.