When doing Corrosion overlay (Inconel, Duplex, Monel) or hardfacing (Stelliting) on Carbon Steel (WCB, LCC etc.), it is usual practice to weld first layer with SS (ER309L), which is also called buffer layer and weld subsequent layers of required weld metal.

Suppose we do 3 mm overlay without buffer layer, then qualified weld metal thickness will be 3 mm to unlimited as per QW-462.5(a) and QW-453.

My question is, if weld 1 mm thick first layer with SS, as a buffer layer and then weld 3 mm of required material (Stellite, Inconel etc.), then what will be the minimum qualified weld metal thickness ? 3 mm or 4 mm ?

In short, should we consider thickness of buffer layer as weld metal thickness while considering qualification range of weld metal ?

My opinion is that, we should consider thickness of only original weld metal (3 mm).

Please share your views.

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