Creep of uncoated and Cu-Cr coated NARloy-Z

Stress rupture creep tests were performed on uncoated and Cu-30vol.%Cr coat ed NARloy-Z copper alloy specimens exposed to air at 482-704 degrees C. The results showed that creep failure in air of unprotected NARloy-Z was preci pitated by brittle intergranular surface cracking produced by stress-accele rated grain boundary oxidation (SAGBO), which in turn caused early onset of tertiary creep. For the protected specimens, the Cu-Cr coating remained ad herent throughout the tests and was effective in slowing down the rate of o xygen absorption, particularly at the higher temperatures, by formation of a continuous chromium oxide scale. As the result of reducing oxygen ingress , the coating prevented SAGBO initiated early creep failure, extended creep deformation and increased the creep rupture life of NARloy-Z over the enti re 482-704 degrees C test temperature range. Published by Elsevier Science S.A.