Microstructure and mechanical and electrochemical properties of martensitic weld deposits developed for welding of a 12%Cr duplex stainless steel

The microstructure and mechanical and electrochemical properties of martensitic weld deposits developed for the welding of a duplex 12% Cr corrosion resisting steel, as well as the experimental procedures used, are described. During the development, it was found that weld metals having matching compositions (and thus duplex structures) to those of 3CR12 had very poor impact properties. This was largely because of the inability to control weld metal grain size. By increasing the proportion of austenite stabilising elements, to produce a predominantly low carbon martensitic weld deposit, it was found that acceptable toughness (≥30 J at 20°C) could be achieved in the as welded condition. The electrochemical properties were designed to be similar to, yet slightly more noble than, those of the wrought 3CR12 plate, thus guarding against possible inhomogeneities in the as cast structure. Cost was also an important consideration throughout the development of these closely matching consumables, since the austenitic filler metals used (e.g. AWS E 309 Mo) were substantially more expensive than the parent plate. It has been shown that cost effective, metallurgically compatible filler metals for 3CR12 can be produced.

MST/651