Effect of Fatigue Under Transverse Compressive Stress on Slit Y-Ba-Cu-O Coated Conductors

The slitting of wide Y-Ba-Cu-O coated-conductor tapes to a width desirable for applications allows for considerable reduction in conductor manufacturing cost. Localized damage induced at the slit edges may be tolerated provided that mechanical cracks formed in the ceramic layers do not propagate deeper inside the conductor due to mechanical forces and thermal cycling to which the strand will be subjected in actual applications. In order to evaluate the effect of slitting, we used fatigue cycling under transverse compressive stress. These tests simulate conditions in applications such as rotating machinery and industrial magnets. Conductors measured had a rolling-assisted biaxially textured Ni-W substrate (RABiTS), or a Hastelloy-C substrate with an ion-beam assisted deposition (IBAD) buffer template. Samples were fabricated with or without a Cu protection layer, added either before or after slitting. For all these geometries, the critical current exhibited no significant degradation during fatigue testing up to 150 MPa transverse compressive stress and 20,000 cycles. Nevertheless, these results do not imply that slitting is not deleterious to the conductor performance under other experimental conditions.