Abstract
Electrochemical jet processing (EJP) is an athermal technique facilitating precision micromachining and surface preparation, without recast layer generation. The role of the microstructure in determining machining characteristics has been largely overlooked. In this study, we show that in order to optimise EJP for a given material, fundamental material factors must be considered to ensure the desired near-surface response in terms of metallurgy, topography and dimensional accuracy. In this work, specimens have been prepared from the same feedstock material (brass, Cu39Zn2Pb), to appraise the role of microstructure in the determination of key removal characteristics, such as resultant topography, removal efficiency and form. Topography is shown to be highly dependent upon microstructure across large current density ranges, whereby the phase ratio is generally the dominant amplitude-defining material property, where preconditions with divergent ratios result in lower amplitudes. The microstructure, specifically the phase ratio, significantly changes the form, where predominantly single-phase conditions result in deeper and narrower features (up to 15% deeper compared with as-received condition). In addition, removal efficiency is greater (by 6%) at low current density for small grained dual-phase conditions, than for predominantly single-phase, due to erosion complementing anodic dissolution. Mechanisms are discussed for these removal phenomena and used to inform industrial practice.
Highlights
Electrochemical jet processing (EJP/EJM) is a non-conventional process that exploits anodic dissolution and was investigated by Ippolito et al (1981) for the purpose of material transfer, where the process physics have been described in detail by Kozak et al (1996)
We demonstrate that microstructural factors affect the resultant nearsurface chemistry, topography and form and that through careful consideration the processing conditions can be informed in order to realise surface design
As the resulting surface after EJP is known to be affected by the low current density area of the distribution as the electrolyte jet traverses the workpiece, the point approach was considered important to understanding the mechanisms of surface generation as well as material removal
Summary
Electrochemical jet processing (in machining mode) (EJP/EJM) is a non-conventional process that exploits anodic dissolution and was investigated by Ippolito et al (1981) for the purpose of material transfer, where the process physics have been described in detail by Kozak et al (1996). Material removal in electrochemical machining (ECM) is achieved by anodic dissolution, as opposed to thermal or shear-based methods, and no white layer or residual stress is induced in the surface, making EJP ideal for high-value applications, where surface integrity is a primary concern. Electrical current is limited in this region due to the relatively high resistance of the film, the current density, J, is largely confined beneath the nozzle, giving rise to localised machining. Localised current density across the electrolyte jet, follows a Gaussian-type distribution, described by Yoneda and Kunieda (1995), which defines the feature form
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