Another Wheel Failure
11-23-2009, 02:58 PM
#22
So who is gonna tell us if this particular wheel is powder coated?
I got 20 beans that says that wheel was powder coated and if you had them tested that they would show that they are signifacantly weaker. Whats more I'll bet that if you ask 5Zigen they would say that powder coating their wheels is a no no
-Rob
I got 20 beans that says that wheel was powder coated and if you had them tested that they would show that they are signifacantly weaker. Whats more I'll bet that if you ask 5Zigen they would say that powder coating their wheels is a no no
-Rob
11-23-2009, 03:05 PM
#23
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Originally Posted by rob.ok,Nov 23 2009, 03:58 PM
So who is gonna tell us if this particular wheel is powder coated?
I got 20 beans that says that wheel was powder coated and if you had them tested that they would show that they are signifacantly weaker. Whats more I'll bet that if you ask 5Zigen they would say that powder coating their wheels is a no no
-Rob
I got 20 beans that says that wheel was powder coated and if you had them tested that they would show that they are signifacantly weaker. Whats more I'll bet that if you ask 5Zigen they would say that powder coating their wheels is a no no
-Rob
11-23-2009, 03:06 PM
#24
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From the link in the first post.
That is correct. No phase change occurs at 350 degrees for any type of metal used in a wheel application. The hottest curing temp needed for an type of powder is 400 degrees. I own a powder coating business and have done 1000s of rims for people with never such an occurance. I'm an engineer by schooling and have taken metallurgy classes so I have a fair bit of knowledge and understanding of metals. no physical properties are changed at 400 degrees for steel, aluminum, or even titanium that is used on motorcycle rims more commonly these days.
11-23-2009, 03:32 PM
#26
From one of the links in the thread that PedalFaster linked:
I'm considering busting out my Material Science books and looking through them. Wouldn't hurt to for me to get a refresh on this stuff anyways.
Question: We are a job shop that was asked to powder coat billet aluminum parts for a customer. The customer asked if the cure cycle will affect the physical properties of the billet aluminum?
Answer: Yes, the cure cycle can adversely affect the strength of the material. Peak substrate temperatures should be below 300°F--ideally 275°F. Aluminum billet material and/or alloys change crystal structure at about 410°F. The crystalline realignment at 410°F causes the previous ductile aluminum to become brittle.
The Aluminum Association Inc. describes it this way: Heating aluminum alloys above 275°F causes granular rearrangement of the metallurgical structure resulting in a significant change of bulk properties. Essentially, the tensile strength of the metal is dramatically lowered, much like a stress relief anneal on a steel piece would do.
Consequently, the resultant substrate is not as strong, nor will pressure vessels made of such treated aluminum (e.g., scuba tanks) hold near the pressure that they were originally rated for.
Answer: Yes, the cure cycle can adversely affect the strength of the material. Peak substrate temperatures should be below 300°F--ideally 275°F. Aluminum billet material and/or alloys change crystal structure at about 410°F. The crystalline realignment at 410°F causes the previous ductile aluminum to become brittle.
The Aluminum Association Inc. describes it this way: Heating aluminum alloys above 275°F causes granular rearrangement of the metallurgical structure resulting in a significant change of bulk properties. Essentially, the tensile strength of the metal is dramatically lowered, much like a stress relief anneal on a steel piece would do.
Consequently, the resultant substrate is not as strong, nor will pressure vessels made of such treated aluminum (e.g., scuba tanks) hold near the pressure that they were originally rated for.
I'm considering busting out my Material Science books and looking through them. Wouldn't hurt to for me to get a refresh on this stuff anyways.
11-23-2009, 04:36 PM
#28
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There are special low temp powders that can be cured at temps below 150°. Your typical powder coater does not use these powders. The common used powders curing closer to 300° most definitely have an adverse effect on T-4, T-6 heat treated aluminum A356.0 and 6061 alloys used in road wheels whether they are gravity cast, low pressure cast, flow formed, billet or net forged. The stronger the base design, the less likely it is to fail when weakened by improper PC.
For those that might argue that brake heat has the same effect, it doesn't. Brake heat is transient. Powder curing is sustained unfortunately, not too dissimilar to annealing some fabricators will perform on 6061 T-6 to make it easier to form or repair.
Your average street guy will never find out about aluminum wheel failures due to powdercoating. Those of use that have been around motorsports for a few decades, hear of them every now and then. At least two well documented instances in Spec Miata in the last 3 years. Post crash metalurgical anaylsis determined PC to be the cause. So yeah, don't believe everything you read on the interweb
Powder coating of any kind voids the warranty on our 6UL and 6ULR wheels.
5Zigen generally makes a good wheel so I would be surprised if the failure shown in the OP was a result of any design or manufacturing deficiency. Will be interested to see what the root cause was,
For those that might argue that brake heat has the same effect, it doesn't. Brake heat is transient. Powder curing is sustained unfortunately, not too dissimilar to annealing some fabricators will perform on 6061 T-6 to make it easier to form or repair.
Your average street guy will never find out about aluminum wheel failures due to powdercoating. Those of use that have been around motorsports for a few decades, hear of them every now and then. At least two well documented instances in Spec Miata in the last 3 years. Post crash metalurgical anaylsis determined PC to be the cause. So yeah, don't believe everything you read on the interweb
Powder coating of any kind voids the warranty on our 6UL and 6ULR wheels.
5Zigen generally makes a good wheel so I would be surprised if the failure shown in the OP was a result of any design or manufacturing deficiency. Will be interested to see what the root cause was,
11-23-2009, 08:15 PM
#30
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I have never seen this occur from PCing forged monoblock wheels. I have powdercoated my last 4 personal sets of Rays/Volk/Prodrive wheels. No problemo thus far...*knock* on wood.