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Heppenstall etchant - Nickel superalloys

Material Name: Nickel superalloys
Recipe No.: 12069
Primary Chemical Element in Material: Ni
Sample Type: Bulk
Uses: Macrostructure
Etchant Name: Heppenstall etchant
Type (Macro/Micro): Macro
Etching Method: Chemical
Etchant (Electrolyte) Composition: 3 parts H20, 2 parts conc. HCl, 1 part H2O2 (35 wt.%)
Procedure (Condition): Preheat slice in hot water, then immerse in etchant. Remove when surface darkens. Rinse and dry.
Note: It, like Canada's, responded quickly, revealing segregation within approximately ten minutes. It also required precautions. Unlike Canada's, however, this etch produced uneven and "patchy" results, and appeared to behave inconsistently. Heppenstall etch produced good definition of interdendritic segregation when these users were able to get this seemingly unpredictable technique to work.
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.