Near-Net-Shape Forming of Metallic Bipolar Plates for Planar Solid Oxide Fuel Cells by Induction Plasma Spraying

Abstract

In one of the present designs of solid oxide fuel cells (SOFC), metallic bipolar plates with gas channels on the surface are used, which consist of a chromium alloy and are manufactured by a time consuming and costly multistep process. To reduce the production time and costs, attempts are made to develop an alternative near-net-shape production method based on RF-induction plasma spray technology. With this process raw powders, as applied for the "conventional" sintering route as well as recycled powders from used bipolar plates, have been applied. The process parameters were adapted to both powders, and the obtained products were qualified. The near-net-shape production requires the formation of a gas channel structure already with the spray process using structured substrates. Therefore, different spray angles occur during the deposition process. The influence of the spray angle on the microstructure of the free-standing parts was investigated. The required gas tightness for grooved profiles with relatively large channel depths and widths can only be achieved using spray angles between 90° and approx. 60°. Then a tilting of the substrate and an adapted design of the gas channel profiles are needed to fulfill the structural requirements for the bipolar plates.