heating to add coating destroys strength of aluminum part.

[gadkinsj]

Some aluminum alloys have their strength destroyed when subjected to high heat and some can be re heat-treated and brought back to a high strength condition. Does someone have a good link to which materials exhibit this characteristic and what mechanism causes this?
I have a part that we are trying to put a coating onto and the coating requires a soak at 800F.
Thanks,

 

[TVP]

You cannot heat Al alloys to 800 F and expect to have a functional component. What coating requires such a high application/curing temperature?

 

[1gibson]

There was a recent powdercoating thread about motorcycle wheels that had good info.

 

[gadkinsj]

I know I tried to post on the motorcycle thread and ask this question and people told me to make my own thread. The component will be heat cycled every 15-20 mins to around 300-325 F, so the coating is designed to act as a releasing agent for a rubber part. I was under the impression that some AL alloys will be able to withstand that kind of heat (obviously losing strength) but then could be re-treated to a Aged condition.

 

[cloa]

Is it 800 F or more like 325 F heat soak (for how long?) that is required?

 

[gadkinsj]

The coating requires 800 degrees for less than 15 minutes to be applied. In application the part will see a 15-20 minute cycle of 300-325 degree.

The question is, after applying the coating at the high temperature, is the aluminum forever going to be compromised, or can I then process it through heat treat cycle and get a good yield strength back say 40ksi or better? (lets say comparable to a 6061 T-6 or 2024 T-3

Why aluminum? This application requires good heat transfer and using steal will slow down the process significantly

 

[CastMetal]

If the coating can be applied at say... 980 deg F this could be done during solution heat treat of 6061 T0 to T4 then aged normally to T6. One thing to note at 300 deg you will not have the book yield strength value. You might have only 60% of that with 6061. 2xxx series aluminum generally holds up better at elevated temp but it is something you should look into.

 

[gadkinsj]

Thank you for the response CastMetal. I think the original intention was to do this with a 7000 series alloy because at the time it was easier to get billets big enough for us to use. Would 7000 series be able to withstand this type of temp treatment? And are there any castable aluminums alloys that would we would be able to treat this way and not lose strength?

 

[swall]

This is probably a dead end,but I'll throw it out anyway. AlliedSignal had a dispersion strengthened high temperature aluminum alloy that could have withstood 800F. AA designation was 8009; AMS spec 4308. Allied sold off the rapid solidified alloys business sometime in the early 2000's, so I don't know if this material is commercially available. And AMS 4308 is listed as inactive.

 

[CastMetal]

Page 129-132 of attached will help you. But in short a 300 deg service temperature is not ideal for most aluminum.