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- Dec 27, 2013
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Mecha What is it about forging ti that makes an oxidizing environment beneficial? I would think just the opposite based on the pains taking to weld it entirely gas shielded.
But you've forged a million times more ti than I have, I'm just curious.
A reducing atmosphere at forging and heat-treating (beta phase transus) temperatures encourages the formation of titanium hydride in ti alloys. At these temps ti can absorb atmospheric gasses into the billet, and this contamination embrittles titanium alloys. In an oxidizing atmosphere the ti quickly forms a thick protective oxide barrier that nullifies atmospheric contamination at these lower temps. I forgot what this type of alloy is called, but I'll find out and post it. I believe there are bronze alloys and others that act the same way.
Welding melts the ti completely which is much worse! Argon gas shields the melted ti from instant atmospheric contamination during welding. Ti gets brittle fast when contaminated with gasses.
Edit: Meant to add that a reducing atmosphere, for some reason, allows gasses to penetrate the oxide layer. It was described as the "kiss of death" by an extremely knowledgeable ti metallurgist who clued me in. To decontaminate the ti requires a full-on remelt.
https://en.wikipedia.org/wiki/Titanium_hydride
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