Development of high performance cast stainless steels for ITER shield module applications

Casting of austenitic stainless steels offers the possibility of directly producing large and/or relatively complex structures, such as the first wall shield modules or the divertor cassette for the ITER, which may lead to simpler component fabrication and major cost savings. Past efforts to use cast steel for these large components were unsuccessful due to lower than acceptable strength in the test components. To improve and validate cast stainless steel as a substitute for wrought stainless steel for shield module applications, a series of test cast steels based on the commercially available CF3M specification have been designed and fabricated. These modifications utilize combinations of Mn and N, which result in significant increases in strength, fracture toughness, and impact properties. These mechanical performance improvements have been achieved without any loss of irradiation performance, corrosion performance, or weldability.