PWHT MULTIPLE TIMES ON THE SAME JOINT OF SA335P91 MATERIAL

[ishtechmech]

How many times PWHT one can perform on SA2335P91 Joints ? what issue may arise if we do PWHT multiple times on such joints . give scientific reasons.

what if the material is carbon steel or low alloy steel?

 

[r6155]

How many times is a multiple for you? 3, 5, 10?
Give scientific reasons.

 

[weldstan]

I limited it to 2 and then required a full cut out and reweld. Excessive surface decarburization was the main reason plus over tempering. In one instance I required pipe spools to be cut out and reheat treated in vacuum furnaces after evaluating microstructure.

 

[EdStainless]

With an alloy like 91 where the creep properties are strongly changed by HT you have to be careful.
Changes in the microstructure will have risks.
You can use multiple PWHT as long as you have verified the resulting properties.