Chemical and electrochemical machining of titanium alloys – a review

Chemical machining (CM) and electrochemical machining (ECM) are fundamental manufacturing techniques employed to generate defect-free, precise surfaces and micro-features in titanium alloy components. Recent advancements have further enhanced these finishing processes through electrolyte jet machining (EJM), chemical-mechanical polishing (CMP), and hybrid-CM/ECM. This investigation reviews and analyses the mechanisms, applicability, methods, material removal rate, and resulting surface qualities of these techniques based on current literature. These processes remove metal at the atomic layer through targeted chemical solutions; they produce defect‑free surfaces without inducing thermal stress or external force. In chemical machining, only chemical solutions are used to remove material through chemical reactions in a controlled manner which is a very slow process (0.1524 mm/hour roughly). The assistance of an electric current is used to increase the material removal rate through anodic dissolution without compromising the quality in ECM, offering better control. A jet of electrolyte is used in electrolyte jet machining (EJM) which improves the process flexibility. A passive surface oxide film slows down the CM, ECM, and EJM processes for most of the electrolytes. The hybrid machining process of titanium alloys was also reported by combining milling and grinding processes. These facilitate the chemical dissolution by removing the passive oxide layer surface on the titanium alloy surface mechanically.