Alloy 718 - Electrolytic polishing

Alloy 718 - Electrolytic polishing

Material Name: Alloy 718
Recipe No.: 12073
Primary Chemical Element in Material: Ni
Sample Type: Bulk
Uses: Microstructure, gamma prime particles
Etchant Name: No data
Type (Macro/Micro): Micro
Etching Method: Electrolytic polishing
Etchant (Electrolyte) Composition: 20% H2SO4, 80% methanol
Procedure (Condition): The simple set up for electropolishing consists of a DC power supply, a 250 ml stainless beaker as the cathode, and stainless steel tongs as the anode. After a 6 micron diamond polish, the sample is electropolished for 20 seconds at 25 volts in a solution of 20% H2SO4, 80% methanol. The sample is rinsed in hot water and fresh alcohol and then cleaned ultrasonically in fresh alcohol.
Note: The electropolished surface is freed of the flow layer and the inert carbides, borides, nitrides and oxides are revealed due to the difference of the electropolishing action. The delta, gamma’, and gamma’’ phases are polished flat and need to be etched to reveal these phases.
Reference: John F. Radavich, Electron Metallography of Alloy 718, Superalloys 718, 625, 706 and Various Derivatives, Edited by E.A. Loria The Minerals, Metals &Materials Society, 1997, pp. 17-26.