Bonding of vanadium- and Iron-based alloys as interlayers for plasma-facing and structural materials in fusion systems

• L2 1 intermetallic phase found at FeCrAl–VCrAl interface. • Interface hardening directly linked to L2 1 phase. • Additively manufactured builds showed B2 phase, unlike sintered samples. • Cr buffer layer proposed to avoid intermetallic formation. • No σ-phase detected in any tested sample across the interface. Vanadium alloys and FeCrAl were investigated as interlayers between tungsten and reduced activation ferritic martensitic steel for fusion system components to avoid formation of intermetallic phase at operating temperatures between 550 and 1100 °C, while maintaining a body centered cubic phase throughout the interface. Physical and mechanical properties need to be graded between tungsten and steel, but recent results showed a significant hardness increase at the FeCrAl to vanadium alloy interface. Here, a sintered sample of these alloys was annealed for extended time, and the microstructure was investigated to provide a better understanding of the phenomena. A comparison with an additively manufactured interface of the same material is provided. An unexpected L2 1 intermetallic phase formation has been revealed using microscopy and synchrotron techniques and will inform future additive manufacturing approaches of the interface. A Cr layer interface as a preliminary solution was proposed between the Vanadium alloy and FeCrAl alloy interface.