If PWHT is in the "normal" temperature range for C.S. PWHT, (say between 1000-1200F), then you will get lots of intermetallic precipitates and might as well not have duplex cladding to begin with. Its corrosion resistance and mechanical properties will be severly impaired.
With the expense of the cladding operation and post weld heat treatment is the cost of the overlay material that significant?
Is a nickel base material like Inconel 625 too expensive?
If this is an ASME Section VIII, Div 1 vessel, can you perform overlay after welding and PWHT of the vessel shell? Or is this a Section VIII, Div 2 vessel?
Thanks for your answers.
We decided to propose a thin (3mm) "625"-cladding. The (1 layer) overlay with 625 can be realised thinner than with duplex or 904L. Also higher cladding speed is possible with 625, there dilution% is not critically with 625.
