Optimization of Superaustenitic Stainless Steel Filler Metals for Welding Advanced Double Hull Combatant Ships

摘要

The performance of welds on superaustenitic stainless steels (SASS) such as AL-6XN has been improved through the use of a new microstructutal development sequence. Thermodynamic calculations were used to isolate the range of possible filler metal compositions, the results of which were confirmed experimentally through alloy construction and EPMA analysis. HED welds on the alloys were used to induce the massive transformation, which is capable of producing fully-austenitic welds with uniform distributions of Mo. SASS welds using such a filler metal should display improved corrosion resistance and weldability over current Ni-base filler metal solutions. The tensile, fracture toughness, and fatigue properties of AL-6XN plate material in the short- transverse (S-T) orientation were studied. The presence of brittle second-phase particles in the form of microstructutal packets has been shown to be detrimental to the mechanical properties of AL-6XN.