Fatigue properties of titanium alloys marked with a pencil
Fatigue properties of titanium alloys marked with a pencil
(OP)
we are currently testing parts made from Ti6Al7Nb - which should behave similar to Ti6Al4V for fatigue life properties. Actually we got an early failure that was unexpected and now we are looking for explanations.
One thing that bothers me is the fact that somebody made pencil marks on the surface of the test specimen. I have something in mind that you should not pencil mark titanium parts but I could not find a reason.
Q1: is it possible that the pencil mark has an influence on fatigue life of titanium parts?
Q2: if yes what is the reason?
Thank's for any Feedback.
Frank
One thing that bothers me is the fact that somebody made pencil marks on the surface of the test specimen. I have something in mind that you should not pencil mark titanium parts but I could not find a reason.
Q1: is it possible that the pencil mark has an influence on fatigue life of titanium parts?
Q2: if yes what is the reason?
Thank's for any Feedback.
Frank





RE: Fatigue properties of titanium alloys marked with a pencil
RE: Fatigue properties of titanium alloys marked with a pencil
RE: Fatigue properties of titanium alloys marked with a pencil
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Plymouth Tube
RE: Fatigue properties of titanium alloys marked with a pencil
RE: Fatigue properties of titanium alloys marked with a pencil
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Plymouth Tube
RE: Fatigue properties of titanium alloys marked with a pencil
RE: Fatigue properties of titanium alloys marked with a pencil
RE: Fatigue properties of titanium alloys marked with a pencil
@TVP yes we have quiet some testing without markings and without early failures - this was the reason for the question of a possible influence. We will follow up and do further rotating beam fatigue testing with markings... Thanks!
RE: Fatigue properties of titanium alloys marked with a pencil
metengr has been identified as the most helpful member of this forum (see the MVP's list on the right side of the page). You would be wise to heed his advice.
TVP has provided something that is a possibility, but it seems so unlikely. Pencil leads are ~ 70 % graphite with ~ 30 % clay and wax. The amount of graphite on the titanium surface couldn't be more than micrograms. That amount shouldn't be able to generate much hydrogen. Titanium can be embrittled by hydrogen, but it isn't as susceptible as high-strength steels.
I think you need to look elsewhere.
Regards,
Cory
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RE: Fatigue properties of titanium alloys marked with a pencil
Nick
I love materials science!