Dimensional Changes during coating process

[bricearnold]

I have a 440c part which goes through a final coating process. Part of the coating process involves baking the material to set it. I need to know how to determine what the maximmum temperature or working temperature that the material can wistand witout moving due to stress relief.

The geometry of the part is such that it is a thin plate .040" tthick with a .021" h x .300" lg. blade on one end. The bottom edge of the blade is coincident with the bottom of the part. This surface has a call out of .0003 flatness.

To manufacture the part, a blank of 440C is first heat treated to RC 30-35. The profile of the part is then EDM'd and the profile is sliced into individual pieces. At this point in the process the part is to print. When we send the part to coating, the final process is to bake it at 450 F. During this process, the tip of the blade can move upto .002"

Once again, I need to find out how to determine my maximum baking temp without the material moving for any material (should I decide to change the material).

 

[kenvlach]

Don't think an answer is possible w/o a determination of residual stress profiles in your part.

The usual remedy is stress relief prior to finish machining.

 

[EdStainless]

Ken has your answer.
If you must bake at 450 after coating, then before cutting you should bake at 500.
What tempering temperature are you using? Are you double tempering? How are you cooling from temper?

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[TVP]

Are you sure that the part has been heat treated to 30-35 HRC? The tempering temperature to achieve 30-35 HRC in 440C stainless steel is > 550 C (1020 F), which should make any subsequent baking at 230 C (450 F) relatively inconsequential with respect to distortion. When you say "sliced into individual pieces", what is the exact machining method? EDM? Abrasive saw?