I am currently working in Ti-Mo alloys with 25wt% and 30wt% Mo. Can anyone suggest a better method for the metallographic preparation of this alloy and a suitable etchant.
You can just take 10% hydrochloric acid for etching polished cross section. Titanium reacts with the hydrochloric acid, but molybdenum does not react, so you can use it to etch structure well (let act for a few seconds).
Dear Dr. Parvathy M.,
many etchants have been developed for titanium and its alloys, but Kroll’s is by far the most commonly used. It is generally quite adequate for nearly all alloys. A simple dilute aqueous HF solution will reveal the structure but is less satisfactory than Kroll’s (1-3mL HF, 2-6mL HNO3, and 100mL water). Because a tight oxide will form on Ti in air, etching is more effective if done immediately after preparation and by swabbing rather than by immersion. Nearly all etchants for Ti and its alloys contain HF, which is a dangerous acid. Contact with HF must be avoided. Handle this acid with extreme care.
For more details, also about the metalographic preparation, lplease see the source at: https://www.buehler.com/solutions/technotes/vol3_issue3.pdf
I suggest you also to have a look at the following interesting technical note:
- Metallographic Preparation of Titanium and Its Alloys
by George Vander Voort (2014)
Available at: https://vacaero.com/information-resources/metallography-with-george-vander-voort/1397-metallographic-preparation-of-titanium-and-its-alloys.html
Good work and best regards, Pierluigi Traverso.
I have never prepared a Ti alloy with that much Mo. I have done many binary Ti samples (but not that much Mo) and alpha-beta and beta Ti alloys using the preparation procedure and etchants listed in the attached document. Good luck!
George
Aas a follower of @George Frederick Vander Voort, I join his recommendations. I can advise his technique Ti-PrepandEtchOnly + etching with berach reagent and selenic acid. It's worth a try. At least in Ti-Al-Nb-Mo alloys, this has an effect. Etching berach and selenic acid should be carried out in the last place.
For the development of Ti and its alloys, one of the suitable methods is by the method of Kroll's -1-3mL HF, 2-6mL HNO3, and 100mL water.
Kroll's is like the nital for Ti alloys. It works but it is not always the best etchant. Please see the attached PPP on preparation and etching Ti and alloys. The Weck reagent for Ti, with the ethanol content lowered per Janina Radzikowska, works much better.
Emil: It is my great pleasure. If you know my work, you know that I am a vast user of color etchants as they are far better at revealing much more information about the structure than any B&W etch. Also, the images are often very beautiful! George
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