1986 Volume 4 Issue 4 Pages 778-783
The first layer ovrelay weld metal with austenitic/martensitic duplex microstructure provides the overlay. welds with better resistance to the hydrogen-induced disbonding than that with the conventional austenitic microstructure containing several percents ferrite as previously reported.
The resistance to the hydrogen-induced disbonding occurring at the bond of the stainless steel overlay weld is strongly affected by the hydrogen concentration at the bond region.
Based on this consideration, the hydrogen distribution in through-thichness direction of the disbond-ing resistant overlay weld was studied and compared with that of the conventional overlay weld.
The main results obtained in this study are as follows.
(1)The hydrogen contents in the first layer overlay weld metals adjacent to the bond of the conventional and disbonding resistant overlay welds were. 25.6 and 16.5 ppm, respectively, at steady state operating condition.
(2) The hydrogen content in the first layer overlay weld metal adjacent to the bond of the conventional overlay weld increased after shut down of operating condition. On the other hand, that of the disbonding resistant overlay welds scarcely increased.
(3) The maximun hydrogen content of the conventional overlay weld described in (2) was 36.5 ppm at 3.24×104 seconds after shut down of operation. That of the disbonding resistant overlay weld was 17.9 ppm at 3.6×104 seconds.
(4) The lower hydrogen content after shut down of operating condition described in (3) provides the overlay weld.with good resistance to the hydrogen-induced disbonding.
