Electrochemical slurry jet micro-machining of tungsten carbide with a sodium chloride solution

• Electrochemical slurry jet micro-machining (ESJM) of WC using NaCl solution is presented.
• Comparison of abrasive slurry-jet (ASJM), electrochemical jet machining (ECJM), and ESJM.
• The material removal mechanism involves erosion of oxide layer and anodic dissolution of unoxidized WC.
• The erosion and corrosion are coupled in determining the machining result of ESJM.

Electrochemical slurry jet micro-machining (ESJM) is a new non-conventional process that couples abrasive slurry jet machining (ASJM) and electrochemical jet machining (ECJM) concurrently. A micro-jet of abrasive particles and electrolytic solution is made to impinge on the target while applying a DC potential between the jet nozzle and the workpiece. ESJM can be used to remove material that is difficult to machine through a combination of erosion, corrosion and synergistic effects. This study focuses on ESJM of tungsten carbide (WC) using a pH-neutral NaCl electrolyte rather than an alkaline solution which is more commonly used in the electrochemical processing of WC. For the studied process parameters, it was shown that the erosion due to ASJM alone was not able to erode the WC, and that the corrosion under ECJM was slow and produced unacceptably wide channels. The combined ESJM process however, was found to involve erosion of the developed oxide layer and subsequent exposure of un-corroded WC, leading to a much higher machining current density, corrosion rate, and machining localization than using ECJM alone. It was also found that the total abrasive kinetic energy, working voltage and solution concentration strongly affected the machining current density, material removal rate and aspect ratio (depth to width ratio). The results indicate that ESJM has a high potential to machine difficult-to-cut metals efficiently and economically.