Influence of nickel content on the etching behaviour and surface characteristics of cupronickel alloys in photochemical machining

Cupronickel alloys are widely used in marine and industrial environments due to their excellent corrosion resistance. This study examines the influence of nickel content on the photochemical machining (PCM) performance of CuNi10 and CuNi30 alloys using ferric chloride (FeCl₃) as the etchant. A full factorial design with multi-objective optimisation via Overall Evaluation Criteria (OEC) was employed to evaluate the effects of etchant concentration, temperature, and etching duration on material removal rate (MRR), surface roughness (Ra), and edge deviation. Results show that CuNi10 yields higher MRR but with poorer surface finish and greater edge deviation. In contrast, CuNi30 exhibits smoother surfaces, lower edge deviation, and superior corrosion resistance. SEM and EDS analyses indicate that CuNi30's finer, uniform grain structure contributes to consistent etching. The study underscores the advantage of higher nickel content in achieving enhanced etching precision, offering valuable insights for PCM optimisation in copper-based alloys.