Advanced Conformal Coatings for Electro-Chemical Machining Tools

Electrochemical Machining (ECM) is a micromachining technique best suited for processing hard-to-machine materials such as tungsten and nickel alloys. ECM is a technique of choice for manufacturing of compact and highly efficient heat exchangers, bladed disks, and many other components of aerospace engines. However, deployment of ECM techniques for advanced microfabrication is limited by the problem of “stray-current attack”. When the power is turned on, the electric fields are distributed far from the cathode tool enabling the etching of the workpiece beyond the designed region due to electric current lines acting over this zone. This deteriorates the surface quality of the workpiece and is particularly a problem when ECM is employed to machine a thick workpiece. RMD Inc. proposes to address this problem through the application of an insulating coating on the ECM tool. RMD Inc. will explore a novel multilayered “nanolaminate” design for the insulating coatings that will be deposited using the Atomic Layer Deposition (ALD). These coatings will be relatively thin (~100 nm), have an excellent adherence to the cathode tool, be pin-hole free, tolerate temperature fluctuations, survive high current densities, and be corrosion resistant from ECM electrolytes. The choices of the coating materials within the nanolaminate structure will be uniquely selected to ensure corrosion resistance, insulating properties, excellent bonding, and good thermal expansion coefficient match to the cathode tool substrate. Approved for Public Release | 22-MDA-11215 (27 Jul 22)