50% HCl electrolytic - Nickel superalloys

50% HCl electrolytic - Nickel superalloys

Material Name: Nickel superalloys
Recipe No.: 12071
Primary Chemical Element in Material: Ni
Sample Type: Bulk
Uses: Macrostructure
Etchant Name: 50% HCl electrolytic
Type (Macro/Micro): Macro
Etching Method: Electrolytic
Etchant (Electrolyte) Composition: 1 part conc. HCl, 1 part H2O
Procedure (Condition): Preheat the slice in hot water. Place slice on anode plate in the solution. Slightly immerse cathode in solution over slice. Use ~0.75 A/cm2. Etch for 3 to 6 minutes. Remove, rinse and dry. Stain electrolytically in 4% H2SO4 at ~0.1 A/cm2 for 3 seconds. Rinse and dry.
Note: All squares from all of these slices were etched by this method. This etchant's definition for all interdendritic segregation severities was clearly superior to that of both "Ferric Chloride" and "3:2:1". It was generally comparable in definition to Canada's and Heppenstall etches. However, it provided more consistent and/or marginally sharper contrast for the black spots when samples from all levels of segregation intensity are taken into account.
Reference: T. Le Roux and D.A. Wells, AN ASSESSMENT AND COMPARISON OF TEE SENSITIVITY OF VARIOUS MACROETCHES FOR ALLOY 718, Superalloy 718-Metallurgy and Applications, Edited by E.A. Loria, The Minerals, Metals & Materials Society, 1989, pp. 109-118.