Welding; AWS E309/E309L not allowed

[Kurniatullah]

i found spec welding overlay and dissimilar weld from my client mentioned that AWS E309/E309L shall not be used when design temperature over than 315degC or when PWHT is required.
my questions is why not allowed?

 

[moltenmetal]

My question is why are you using 309 in a situation where PWHT is required? Perhaps then we can better understand the situation. 309 itself is a high temperature alloy but IIRC it is also an alloy used for carbon- to- austenitic stainless welds. Those welds themselves should be subject to temperature limitations due to the inherent problems caused when welding two materials together which have vastly different thermal expansion coefficients...

 

[weldstan]

The large dissimilar thermal expansions will limit the number of thermal cycles before eventual failure. While PWHT will temper the HAZ of the ferritic material, it will not relieve stress. Stress will be reintroduced upon cooling because the 309 weld metal will contract at nearly twice the rate of the ferritic base material thereby creating high shear loads at the fusion line.

 

[Kurniatullah]

my client suggest E NiCrFe-3, is it correct?
i think incorrect due to different SFA no.

 

[metengr]

Most likely the temperature limitation for the dissimilar metal weld is a combination of thermal expansion issues and local carbon migration that occurs above 425 deg C and during PWHT, which renders the ferritic side of the DMW joint prone to creep damage in elevated temperature service.

Yes, AWS 5.11 Class ENiCrFe-3 or Alloy 182 is fine for DMW between carbon/low alloy and stainless steel.