抄録
It was found out that the first layer overlay weld metal with an austenite/martensite duplex microstructure provided the overlay welds with between hydrogen-induced disbonding resistance than that with the conventional austenitic microstructure containing several percent ferrite.
The mechanical properties of the disbonding resistant overlay weld was studied in the previous report.
The purpose of the present study is to determine the metallurgical properties of the overlay weld with the 15%Cr-8%Ni duplex weld metal. The main results obtained in this study are as follows:
1) The Actl and Ac3 temperatures of the duplex structure are 510°C and 630°C, respectively.
2) The duplex structure consists of austenite and martensite after regular post-weld heat treatment (PWHT) at 700°C for 20 hours.
3) Coarse planar grains, which may affect the disbonding resistance of overlay weld, were scarcely observed in the overlay weld metal adjacent to the bond between the duplex weld metal and the base metal.
4) The width of carburized zone in the duplex weld metal is almost equal to that of the conventional weld metal after PWHT.
5) The width of transition zone of Cr and Ni concentrations at the bond of the weld with the duplex microstructure is larger than that of the weld with the conventional austenitic microstructure.
