Have trouble with bend test
11-21-2007, 03:52 AM,
#1
Have trouble with bend test
Hi Gordon and everyone,
My trouble is bend test that was borken when bend the sample after coating.

I had try to shot peen and annealed the samples, but it was still broken.


1.The sample material is Ti-6Al-4V.
2.The powder is Amdry 500F
3.Bend test requirement:
0.5 inch diameter mandrel to bend a minimum of 100 degrees
Regards, William
Reply
11-21-2007, 04:21 PM,
#2
RE: Have trouble with bend test
Hi William,

Just to be clear, is your whole test piece breaking before you reach 100 degree bend or just coating failure? If it is just coating failure, can you describe failure in detail (photo would be good) and thickness of coating?
Reply
11-21-2007, 06:18 PM,
#3
RE: Have trouble with bend test
Hi Gordon,
Thanks for your reply.
Sorry, I didn't say clear. The Ti panel and coating was broken together when I bend the sample. So I didn't inspect the coating that it is Ok or No.
After Coating, why did the Ti panel be broken when I bent it?

Best regard,

William
Regards, William
Reply
11-21-2007, 06:42 PM,
#4
RE: Have trouble with bend test
Hi William,

Good to hear its not a coating problem Cool, but make fully sure by testing a non-coated panel.

It looks like your test panel material just does not have the ductility required for this test. Are test panels supplied from your customer? If so I would contact them. If you have sourced the panels yourself, I would go back to your supplier and specify a more ductile form. Is the panel thickness correct for this test? The thicker it is the less it will bend.
Reply
11-22-2007, 03:25 PM,
#5
RE: Have trouble with bend test
Hi Gordon,
The sample size is 1.0" x 6.0" x 0.063".
I did some test as follow:
1. before coating, bent the sample: The panel no broken
2. after grit blasting, bent the sample:The panel no broken
3. after preheat, bent the sample: The panel was broken
4. after coating, bent the sample: The panel was broken

I tested other matreral panel (example:410SS or IN718 ) that was no this phenomenon.

Best regards,

William
Regards, William
Reply
11-22-2007, 03:50 PM,
#6
Embrittlement of titanium
Hi William,

This is getting a little more interesting. What process and process gass are you using for spraying and preheating? What temperature does the panel see during preheat and coating?
Reply
11-22-2007, 04:30 PM,
#7
RE: Have trouble with bend test
Hi Gordon,
Reply your question.

1.Plasma parameter:
9MC plasma systerm
9MB Gun
733 nozzle
process gass: Ar/He
Coating material: Cu-Ni-In (Fine)

2.During spraying temperature and gass:
Preheat: ~200 degree F
Coating: ~300 degree F


Regards,

William
Regards, William
Reply
11-22-2007, 05:07 PM,
#8
Embrittlement of titanium
Hi William,

If you are using Ar/He plasma for preheating and spraying, that discounts my thoughts somewhat that it might be hydrogen or nitrogen embrittlement from the plasma process.

It might be helpful if you repeat your tests at each stage of processing, but measuring and recording the angle of bend at failure. Those panels that that survive 100 degree bends, just keep on bending until failure. At least this will give a more quantitative picture of your problem. You may need to do more than one test at each stage to ensure it is not just natural variation between samples.

Titanium can be made quite brittle when it absorbs gasses like hydrogen and nitrogen. This is one reason Ar/He plasma is usually specified for spraying onto titanium substrates, though I don't know if Ar/H2 or N2/H2 plasma spray has actually been shown to have any detrimental effect. There is certainly a definite effect when spraying titanium coatings though.
Reply




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