electrolytic etching of Hastelloy X 1

[mwccwi]

We are trying for Aerospace qualification for resisatnce welding and the testing that we have done so far has all been positive. The problem is we need to be able to do the section testing in-house, hourly per customer requirements. It would be insane to attempt to run production without having the in-house ability to perform the production testing.
Does anyone have leads to where I can find suitable equipment for the electrolytic etching for the production witness specimens?
Or have advice for me.

 

[tomwalz]

TRY HPA

High Performance Alloys

http://www.hpalloy.com/

Nice folks. Incredible resource and very good supplier.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[WKTaylor]

mwcci... I presume You are resistance welding per AWS D17.2?

The cleaning process used for production parts MUST be used for Your production witness parts. SO, what ever process You have decided-on for Your production parts is what should be used 100% for Your test samples... and/or be prepared to destructive test production parts on a random/statistical basis.

Hastelloy is a high nickel alloy that is a bear to etch. I suspect a cocktail of strong/dangerous acids may be required. What I have used at depot is mixture of A-A-59105 [O-N-350] Nitric Acid + MIL-A-24641 Hydroflouric Acid + Water [remaining]. Nothing triffling about this mixture: Very dangerous stuff.

I Have also heard of high concentration A-A-55820 phosphoric acid combined with non-woven abrasive cleaning pads.

Sometimes aqueous or solvent precleaning, followed by light particle abrasive cleaning methods, works 'best' on high nickel alloys.

Regards, Wil Taylor

Trust Me! I'm an engineer!

Trust - But Verify!

We believe to be true what we prefer to be true.

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[mwccwi]

Thank you, Wil Taylor,
I am trying to avoid the dangerous chemicals (no hydrofluoric or ferric chloride) this is why I am looking into the electrolytic etching using oxalic acid as the etching reagent (this is what was used in my college metallurgy lab) . I will have to train production QC to perform this process and I don’t like the idea of using the etching reagents that produce the toxic gasses.

 

[WKTaylor]

mwccwi...

Suggest asking this question on the metals and metallurgy forum.

http://www.eng-tips.com/threadminder.cfm?pid=330

Regards, Wil Taylor

Trust Me! I'm an engineer!

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[Maui]

What exactly are you trying to reveal in the microstructure by acid etching? Oxalic acid is typically used for ditching tests on austenitic stainless steels. It preferentially attacks the grain boundaries. And the fumes from this etching practice, while not as dangerous as hydrofluoric acid, are still poisonous. You will want to do this under a chemical hood with gloves and a good air flow.

Maui

 

[mwccwi]

Maui,
The microetchs for lower power magnification (60X) to measure actual weld size and gross defects. Haste X is a nickle based super alloy akin to inconel.
Thanks for the the caution for safety.

 

[jwhit]

Aqua-Regia plus a splash of 30% hydrogen peroxide might do the trick, but do it in a very good fume hood. It may need a couple repetitions. It is more of a macro-etchant, but for your application may work.