Pulse electrochemical machining on Invar alloy: Optical microscopic/SEM and non-contact 3D measurement study of surface analyses

•Invar alloy was electrochemically polished and then subjected to PECM (Pulse Electro Chemical Machining) in a mixture of NaCl, glycerin, and distilled water.•Optical microscopic/SEM and non-contact 3D measurement study of Invar surface analyses.•Analysis result shows that applied voltage and electrode shape are factors that affect the surface conditions. In this study, Invar alloy (Fe 63.5%, Ni 36.5%) was electrochemically polished by PECM (Pulse Electro Chemical Machining) in a mixture of NaCl, glycerin, and distilled water. A series of PECM experiments were carried out with different voltages and different electrode shapes, and then the surfaces of polished Invar alloy were investigated. The polished Invar alloy surfaces were investigated by optical microscope, scanning electron microscope (SEM), and non-contact 3D measurement (white light microscopes) and it was found that different applied voltages produced different surface characteristics on the Invar alloy surface because of the locally concentrated applied voltage on the Invar alloy surface. Moreover, we found that the shapes of electrode also have an effect on the surface characteristics on Invar alloy surface by influencing the applied voltage. These experimental findings provide fundamental knowledge for PECM of Invar alloy by surface analysis.