The effect of high temperature on TP 321H stainless steel

[SukhpalSingh]

What is the effect of exposure to high temperature on stainless steel TP 321H, I have checked the hardness after heating and found it is 250 HB higher than the standard value and the surface color turns to blue? I have found that many resources called this phenomenon as "Heat tint"?

 

[XL83NL]

What is your definition of high temperature - for example 600 °C? Is this temperature caused by a process condition (e.g. hot gas or fluid), or fabrication related (e.g. welding or cawing/cutting)?
Yes, heat tint is something that is usually observed after welding, on the pipe's surfaces. It is dependent (amongst others) of material, temperature, and the composition of the surrounding gas, see e.g. AWS D18.2. Google is your friend.

 

[EdStainless]

When you get above about 300C in air you start picking up heat tint. It starts with pale yellow and gets darker as the temp rises.
When you get to about 500C you would start sensitizing regular stainless (forming Cr carbides). In 321 though you are forming Ti carbo-nitrides. These do push the hardness up a little, but they should be fine and well dispersed.
First you can't get a good hardness with the heat tint in place, it is Cr oxide so it is very hard. Secondly, depending on the time and temp the stabilizing precipitates can raise the hardness.
But what is a 'standard hardness', I hope that it is the one that you took using the same machine on the that material before exposure. You can't compare to anything else.

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P.E. Metallurgy, Plymouth Tube