Advances in the interpretation of the material removal by studying the surface of nitriding steel for pulsed electrochemical machining

Removal techniques offer broad opportunities in the machining of high-strength materials. Besides typical difficult-to-machine non-ferrous materials such as titanium alloys and nickel-based alloys, high-strength steels are also receiving increasing attention. However, due to lower alloy quantities these have a higher undesirable corrosion tendency. This increases the challenges in electrochemical precision machining, which typically occurs in a saltwater environment.
This research shows investigations of the surface after pulsed electrochemical machining (PECM) of nitriding steel 31CrMoV9. Using the material characterization method DIN SPEC 91399, the removal is analyzed as a function of current density by varying the voltage and sinking speed. The surface was studied by a combination of visual inspection and a morphology analysis using DIN EN ISO 25178. Three clearly distinguishable dissolution areas were found. Besides the visual presence of the passivation, inhomogeneities in the removal diagram were traced back to a pronounced increase of roughness of the machined surface.