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Etch acid for Inconel 718 and 903
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What would be a good etch acid to use on polished coupons of Inconel 718 and 903 that would show a recast layer in the microstructure where the coupon was cut using an electric discharge machine.
Bob Westonmetallurgy lab technician - Arkansas City, Kansas
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I would try preparing an Inconel Micro-etch solution that I use myself. For 2.5lts you require: 1ltr conc hydrochloric acid, 50mls of 40% Hydrofluoric Acid (take GREAT CARE WHEN HANDLING THIS SUBSTANCE), 1.25lts of de-ionised water and 200mls of Hydrogen Peroxide (100 vols). Cycle time: 30secs at 25 degrees Celsius. This solution is highly acidic and you must observe all relevant Health and Safety legislation applicable to your workplace when using this solution.
Good luck and all the best for the New Year.
Nigel D Gill, B.Sc. MIMF AIEMA MRSC- Blantyre, Glasgow, Scotland
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Glyceregia is a common etchant for nickel-based alloys. The composition and use instructions are as follows:
15 mL HCl
10 mL glycerol
5 mL nitric acid
Mix fresh for each use-- do not store. Swab the etchant, do not immerse. It has a useful life of < 20 minutes. As it turns color, it becomes overly aggressive. When orange, it can give off Cl gas. Do not breathe in the fumes (use under a hood). Discard properly after about 20 minutes.
Toby PadfieldAutomotive module supplier - Michigan
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This response is for Nigel Gill, Blantyre, Glasgow, Scotland. Thank you for your response to my question about an Inconel Micro-etch solution. I do not know the meaning of the (100 vols) placed behind the amount of Hydrogen Peroxide in your receipe of the solution. Does it have to do with the strength of the H2O2 or does it mean that you would have reached 100% of the 2.5lts volume?
Bob WestonCoating Metallurgy - Arkansas City, KS, USA
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Bob,
The Hydrogen Peroxide that I use has a strength of 30%, here in Britain it is sold in 1 litre bottles with the term 100 vols added in brackets thus: 30% Hydrogen Peroxide (100 vols) I hope this clears up any uncertainty for you. Good luck with your Inconel etching but please do take care if using Hydrofluoric Acid.
Nigel D Gill- Glasgow, Scotland
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Bob,
Has the Inconel Micro-etch solution I mentioned worked for you?
Nigel D Gill, B.Sc. MIMF AIEMA MRSC- Glasgow, Scotland
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Could Mr. Nigel Gill please tell me where he acquires 100 vols. hydrogen peroxide in the U.K., as I need a very small amount for cleaning cracks in old china and chemists are unable (or unwilling) to supply it?
Lindsay Lock- Norwich, Norfolk, UK
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What would be a good etchant acid to use on polished coupons of Inconel 718 and 903 that would show a recast layer in the microstructure
Bala Pratapstudent for project - Vellore
June 11, 2009
Regarding hydrogen peroxide, the term "volume" refers to concentration (strength) in the following manner. Example - 100 volume: The quantity of oxygen gas evolved from the liquid upon complete decomposition occupies a volume(at room conditions) 100 times greater than that of the liquid. 100vol. peroxide is 30%H2O2 in water. Drugstore variety (3%) is therefore 10volume. I hope this helps.
Greg Petersonchemical engineer, aerospace - Anaheim, California, USA
December 28, 2011
Q. The Inconel etching discussions previously posted cover a flat coupon, with no corners, or trapped spaces. We are looking for a pre-etch, to prepare for an epoxy bond, a specimen with an inside corner, and many possible entrapment spaces.
Any thoughts on using plain Muriatic Acid - 50% diluted (yielding around 5% concentration), applied to a heated specimen with a Q-tip, left to sit for a few minutes, washed off with a water bicarbonate soda mix, DI water rinse, and dried, as a possible process for pre-etch in preparation for an epoxy bond?
shop engineer - Upland, California, USA