TWI Industrial Member Report Summary 525/1995
Autogenous weld deposits in high alloy austenitic stainless steels tend to show lower corrosion resistance than the parent material, as a consequence of microsegregation of alloy elements, notably Cr and Mo, to interdendritic regions. Previous work at TWI on melt runs produced by the tungsten inert gas (TIG) process showed that higher pitting resistance was obtained by reducing arc energy. The objectives of the current work are:
- To model the general relationship between arc welding conditions and alloy element microsegregation.
- To improve the corrosion resistance of welds in high alloy austenitic stainless steels.
In this report, published literature, relating to the theory of microsegregation during alloy solidification, has been reviewed and a series of surface melting treatments, using a CO2 laser, has been performed on (i) parent austenitic stainless steel meeting UNS S31254 and (ii) a series of TIG melt runs in similar material. The surface treatments have been assessed metallographically and by pitting corrosion tests.