Observations on cutting edge radius effects in cryogenic machining of porous tungsten

Porous tungsten is a refractory metal commonly used to manufacture dispenser cathode pellets. To produce the required geometric shape of a cathode, precision machining of the emitting surface is necessary. Because dry machining leads to excessive tool wear and smearing of surface pores, a plastic infiltrant is used to both prevent smearing and lubricate the cut. In order to develop a sustainable alternative to this plastic infiltration process, infiltrant-free cryogenic machining of porous tungsten has been identified by previous studies to be capable of producing excellent levels of surface porosity [1-3]. Cryogenic cooling during machining of porous tungsten allows for controlled brittle fracture machining, leading to relatively poor surface roughness [3]. Consequently, improving the surface quality of cryogenically machined porous tungsten surfaces is a necessary condition for the successful implementation of this technology.