Hastelloy B, B2, B3, N, and W alloys

Hastelloy B, B2, B3, N, and W alloys

Material Name: Hastelloy B, B2, B3, N, and W alloys
Recipe No.: 12061
Primary Chemical Element in Material: Ni
Sample Type: Bulk
Uses: General microstructure
Etchant Name: Chrome-regia
Type (Macro/Micro): Micro
Etching Method: Immersion etching
Etchant (Electrolyte) Composition: The preferred etchant for this family of alloys is chrome-regia (1 part chromic acid to 3 parts reagent grade HCl). Stock chromic acid is made by mixing 300 grams chromic acid with 300 ml of hot water.
Procedure (Condition): For immersion etching, it is equally important to work with a wet, freshly polished surface, (i.e., follow step VIII for electrolytic etching). The wet sample is then immersed face up into the chrome regia for 1 to 3 seconds, depending on heat treated condition and sample size. Then pull sample, put under running water, rinse with methanol, and blow dry. If etch is too light, follow procedure described in Step VIII A4.
Note:
1. The sample must have a fresh polish. If the surface has been dry, even for a few seconds, give the sample 6 to 10 laps on final .05 micron alumina (Linde "B") cloth then place directly under running water and swab with a cotton pad.
Important Sample surface must be kept wet.
2. Put sample face up in etchant. With good overhead light to visually see sample surface: make contact at end or corner of sample with anode probe, dip carbon cathode into etchant watch to see any surface change – break contact.
3. Important Before removing sample from etchant, agitate to remove any film on surface. Pull sample and put under running water. Rinse with Methanol, then place sample under hair dryer until it is thoroughly dry.
4. If etch is too light and needs to be heavier, do not take sample back to running water and then into etchant. Instead it must go back to the final cloth for 6 to 10 laps making sure that no part of surface dries failure to do this can, and most likely will, result in staining. If the sample does stain do not try to remove stain on final cloth. Rather, go back to the papers at least to the 400 and 600 grit; then 9 micron diamond and then to 0.05 alumina – and again, keeping sample surface wet, repeat as described before.
Reference: Website https://www.haynesintl.com/tech-briefs/general-haynes-international-information/metallographic-preparation-of-hastelloy-and-haynes-alloys-(H-1107), 2019.