Tensile fatigue behavior and crack growth in GdBa₂Cu₃O_7−x/stainless-steel coated conductor grown via reactive co-evaporation

(RE)Ba₂Cu₃O_7−x (REBCO) conductors have the potential to enable a wide range of superconducting applications over a range of temperatures and magnetic fields (Vincent et al 2013 IEEE Trans. Appl. Supercond. 23 5700805), yet AC applications and devices with a charge/discharge cycle may be limited by the conductor fatigue properties. Here the fatigue behavior of GdBa₂Cu₃O_7−x (GdBCO) conductors grown by reactive co-evaporation on stainless-steel substrates is reported for axial tensile strains, ε , up to 0.5% and 100 000 cycles. Failure mechanisms are investigated via microstructural studies and compared with a commercially available IBAD/MOCVD REBCO conductor. Results show that GdBCO/stainless-steel conductors retain their transport critical current for 10 000 cycles at ε  = 0.35% and ε  = 0.45%, and for 1000 cycles at ε  = 0.50%. The main cause of fatigue degradation in GdBCO conductors is crack propagation and delamination that initiates at the edge of the conductor due to manufacturing defects. (paper)