Microstructure Evolution in AISI 430 Ferritic Stainless Steel Welds Treated with Aluminum and Titanium Powder Mixture

Abstract

Ferritic stainless steel particularly the AISI 430 standard grade is a candidate material for radiation shielding in nuclear reactors for power generation at competitive cost than the workhorse AIS1 316L austenitic grade. But its widespread application as the next generation energy material in nuclear reactor is limited by the loss in mechanical properties arising from grain coarsening and other phase transformations in the heat affected zone of the material post-fusion welding. Thus, in this work, attempt was made to resolve the challenge of grain coarsening in fusion welded AISI 430 ferritic stainless steel for improved mechanical properties. Specifically, the ductility and tensile strength of AISI 430 ferritic stainless steel welds treated with mixture of aluminum and titanium powder was investigated in relation to the microstructural evolution in the weld. The columnar structure in the as-welded condition transited to equiaxed grain with lower percentage of delta ferrite in the powder-mixture treated welds. In this condition, the ductility and the tensile strength of the treated weld marginally improved by 5 percent. The present work in relation to existing work in this space established that powder mixture of aluminum and titanium is capable of producing defect free structural welds in ferritic stainless steel though with marginal improvement in mechanical properties