Bipolar Proton Exchange Membrane (PEM) fuel cell plates are composed of flat pieces of graphite with channels or trenches machined into the face of the plate so that gases can flow in the channels of the plate. The operation of the fuel cell is dependent on the flow of oxygen and hydrogen gases around a fuel cell stack, which is composed of many thin plates connected to each other in very close proximity. Owing to the brittle nature of graphite, bipolar plates are now made from nickel-chromium alloys that are coated with a thin solid layer of CrN or TiN to improve corrosion resistance. However, nickel-chromium alloys are notoriously difficult to machine. This paper describes the micromachining of fuel cell plates that are machined at very high speeds in order to produce high cutting tool life and low surface roughness using novel nanocrystalline diamond and titanium coatings that have been specifically designed to cut strain-hardening alloys at extremely high speeds.
['Mark J. Jackson', 'Grant M. Robinson', 'Mike Brady']
Micromachining of bipolar plates used in proton exchange membrane fuel cells