The Dependence of Surface Finish on Material Precondition in Electrochemical Jet Machining

Abstract

Electrochemical jet machining (EJM) is a non-conventional machining process whereby material is removed by jet-based anodic dissolution phenomena. As a machining process, EJM is capable of selectively texturing conductive materials, however there are aspects of the technique that have been subject to only limited study. The effect of material precondition on the resulting surface texture is studied here for polycrystalline copper sheet (C101), and the influence of increasing grain size and plastic deformation on the resulting surfaces is explored. The resulting surface after EJM is shown to be fundamentally dependent on the material precondition, a factor which has been largely overlooked to date. It was found that increasing room-temperature rolling treatments led to surfaces with slightly smaller cubic pores across all current densities appraised. For prior-annealed large-grained materials, low porosity ordered surfaces can be achieved, and subsequent cold-rolling leads to the creation of band-type features after EJM. This results in discontinuous material removal and higher surface roughness at mean current densities between 100 – 300 A/cm2. Beyond 300 A/cm2, the effect of the cold-rolling treatment is overcome. In addition surface roughness after EJM for individual grains is shown to be intrinsically dependent on the grain orientation, supporting prior electrochemical research, although the contribution this makes may be attenuated by increasing current density.