Machining of proton exchange membrane fuel cells using micromilling tools

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, fuel cells 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 development of micromachining processes that allows fuel cells plates to be machined are very high speeds using novel nanocrystalline diamond and titanium coatings that have been specifically designed to cut strain hardening alloys at extremely high speeds