Microstructure and Mechanical properties of Borated Stainless Steel (304B) GTA and SMA welds

Abstract

Borated stainless steels are used in nuclear power plants due to their high capacity to absorb thermal neutrons.
Borated Stainless Steels are being used to control neutron criticality in reactors as control rods, shielding
material, spent fuel storage racks and transportation casks. In the present study, an attempt has been made
to investigate the microstructural and mechanical properties of the borated stainless steel welds made on
10 mm thick plates, using SMAW and GTAW welding processes. Microstructural investigations revealed that
the fusion zone in GTAW exhibited dendritic structure with eutectic constituents in interdendritic regions. GTA
welds failed in the partially melted zones formed (PMZ) immediately adjacent to the fusion zone, while the
SMA welds failed in the base metal because of the high heat input used per pass in GTAW process resulting in
larger PMZ. The heat input in GTAW was very high compared to the SMAW while both the welds exhibited high
joint efficiencies, SMA welds were found to be superior. Impact testing revealed that welds made using SMA
exhibited significantly higher toughness as the filler does not contain boron. It has been concluded that high
efficiency welded joints can be made on 304B plates using both the processes.