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Etching of Forged Cobalt-Chromium-Molybdenum Alloy
Q. I am currently conducting a research about plasma nitriding of forged CoCrMo alloy (Low carbon). I have to etch the treated specimens in order to observe the microstructure of the alloy. The etchants should reveal the grains but not harm the compound and/or diffusion layer. I have tried;
1. 97% H2O2 + 3% HCl
2. 50% H2O2 + 50% H2O2
3. 75% HCl + 25% Nitric Acid
4. Pure HCl
and I have heated the specimens (about 80 °C), heated the etchants, etc. so far. But none of these methods/etchants worked out for me. Unfortunately electroetching is not an option since I don't have the required system nor time. I would appreciate your suggestions. Thanks in advance.
Ataturk University - Erzurum, TURKEY
2007
A. I'm doing and researching for new etchants for Co-Cr-Mo-C alloys, none of those available on the literature seems to work out for me neither but, I tried 100ml H2O2+50ml HCl, to reveal the macrostructure the time was approx. 10 hours or so, others authors used the same etchant but in an 6:1 HCl+H2O2 for 8 seconds, didn't work for me.
"applied Metallography"
by George F. Vander Voort
on
AbeBooks
or
Amazon
(affil links)
Try to get this paper "Selection methods for etching carbides in MAR-M509 co-base superalloy and acquisition of their images" Materials characterization, 56 (2006) pp 325-335.
Other etchant: 1.5 g CuCl2+33 ml H2O+ 33 ml HCl+ 33 ml ethanol
Another one: two stages etching
SOLUTION A: 21 ml H2SO4 + 15 ml HCl + 21 ml HNO3 + 21 ml HF+22 ml H2O
SOLUTION B: 40 ml of solution of 1 g CuCl2.2H2O + 5 ml H2O+40 ml HCl+ 20 ml HF
5 minutes in solution A and then 5 minutes in solution B but times can vary you should try your own (Vander Voort book), if neither of them seems to work out let me know, I'll send you another etchants, or at least try to.
- Tandil, Buenos Aires, Argentina
A. Hi
Try this etchant:
15 ml HNO3+ 15 ml acetic acid
[on
eBay or
Amazon] + 60 ml HCl + 15 ml H20
I have successfully etched with HC Co-Cr-Mo alloy but you can also try for LC and see how it works. In my specimens the grains of the matrix etch and the carbides are not affected. I would love to know if you find an etchant that etches grain boundaries- it would be convenient.
Most researchers try electroplating but I understand how cumbersome it can be. Good luck and let me know if you come up with any success with this or something else.
Researcher - Boston, Massachusetts
2007
I recently had success with another etchant
6:1 HCl -H2O2
it is a good one etches the grain boundary.
again I tried it with HC alloy.
See how it works for your alloy.
- Boston, Massachusetts, U.S.A.
2007
Q. We want to develop the uniform Microporous structure by etching prior to drug coating on L 605 cobalt chromium tungstan alloy; we are using the FeCl3 solution as a etchant.
Abhishek Masalawalaproduct designer - Surat, Gujarat, India
February 1, 2008
Q. Hi, I'm Mas Ayu, currently student in Universiti teknologi malaysia. I looking on how to etch CoCrMo for my studies. Hope everyone can help me. TQ
Mas Ayu HassanStudent - Johor, MAlaysia
December 30, 2010
Hi Mas. Several good answers were provided already. Please try your best to pose continuing questions in terms of what has been offered and keep the dialog moving forward. Starting over, or running it in circles will only kill off the discussion :-)
Thanks and Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 7, 2011
Q. Hi, my friend
I have a research project about fsx-414 cobalt based superalloy. I have some specimens. One of them is fsx-414 that I can etch with 92% H2SO4 - 5% HCl - 3%HNO3. But I can't etch another specimen that is:
1. fsx-414 solution anneal
2. fsx-414 solution anneal and aged in 800 °C
3. fsx-414 solution anneal and aged in 900 °C
4. fsx-414 solution anneal and aged in 1000 °C
I try a lot of etchants that can't etch them, so if you know a good etchant and method for etching them please help me.
- Ahvaz, Iran
Q. I made an etch of 25 ml H2O2 and then 225 ml of HCl. I have 4 CoCrMo samples of varying diameter, about 60 mm to 10 mm, and I cleaned them with ether after polishing. I then poured some of the mixture over them once it had gone yellow, and washed that of once the green/blue colour was made. Seeing this there will be no grain structure, but after a few minutes the H2O2 HCL was fizzing and I just dropped the samples into the beaker [beakers on
eBay or
Amazon]. After a few minutes and the colour being green I poured the samples out and washed off the mix with water. This gave me the grain structure. I have tried this with a few samples now and it seems to be working, but it is a very dark etch.
Can anybody let me know if this would work for them, or if they have an etch that is better. :)
- Glossop, Derbyshire, England
February 5, 2015
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