Ferric chloride etchant - Nickel superalloys

Ferric chloride etchant - Nickel superalloys

Material Name: Nickel superalloys
Recipe No.: 12067
Primary Chemical Element in Material: Ni
Sample Type: Bulk
Uses: Macrostructure
Etchant Name: Ferric chloride
Type (Macro/Micro): Macro
Etching Method: Chemical
Etchant (Electrolyte) Composition: 75% conc. HCl, 21% FeC13, 3.5% conc. HN03
Procedure (Condition): "Activate" the slice by immersing it for 5 - 10 minutes in 50% conc. HCl in hot water. Transfer the slice to the "Ferric Chloride" etch for a nominal 45 minutes. Swab with a cloth rag as needed to make the stain less dense.
Note: It was a sufficiently stable etchant for all of the squares to be processed through the same batch. The earliest visible effect during etching was the emergence of grain pattern after about 6 minutes. It required 30 minutes or more for the interdendritic segregation to emerge, and gave clear evidence of its presence only in the square taken from the "top" slice.
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.