ETA phase in A286 Alloy

[johngkn]

I have a drawing note that says: ETA Phase to be .004" Maximum. this is for a forging which is supplied in the heat treated condition RC 32-38. Based on my limited knowledge of this phase I will assume like all metallurgy this phase is developed during the forging temperature and operation and then enhanced during the heat treatment cycle?
I do have limits on my max. forging temps, so I will also assume (bad word) that the lowest temp I can get away with forging the better off I will be.

Are these logical assumptions?

Thanks
John

 

[metengr]

Here is a tip, go here and download this dated but excellent reference on A 286 material to understand handling, heat treatment and limitations....

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720022813_1972022813.pdf

,,,,go to bottom of page 8 and top of page 9 for information.

 

[TVP]

John,

Excellent reference from metengr. As you can see, the eta phase develops during aging of a previously solution treated part. Hot forging should not produce much eta phase, and even if it does, the solution treatment should re-dissolve it. How are you cooling the forgings? How is the solution treatment being done? The parts must be rapidly cooled from 980 or 900 C. Aging should be done at 700-720 C for 16 hours followed by air cooling.

 

[johngkn]

metengr, thanks for the resource to review, this will be very helpful for me.
TVP, I have 2 specs and a PO requirement to comply with, the RC 32-38 comes from the PO, even though the 2 specs only give min hardness requirements to meet one is Rc28, the other Rc29. Solution temp to be 1650F (specs) 1 spec has oil or water quench, the other air cool. Then there is a double age: 1300F 16hrs, then 1200F 16hrs. I have to get ahold of the end user and find out where the PO requirements are coming from since they are the owners of the material specs.

Thank you both for your information, it is great to have a forum to tap into the vast knowledge and experience out there.

 

[TVP]

As I mentioned previously, the parts must be rapidly cooled after solution treatment. They can be air cooled after forging, but not from solution treatment.