Oxidation kinetics of Cu-30vol.%Cr coating

The oxidation kinetics of a Cu-30vol.%Cr coating were studied in air over the temperature range from 500 to 700 °C. The CuCr coating was deposited on a Cu-15vol.%Nb substrate by co-evaporation of Cu and Cr from a single CuCr composite target in a vacuum chamber. The coating microstructure was characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The coating microstructure consists of an intimate mixture of Cr particles in a Cu-rich matrix. The size of the Cr phase was less than one micrometer. Thermogravimetric analyses show the oxidation kinetics to be parabolic at all investigated temperatures. The activation energy of oxidation was calculated to be 24.8 kcal mole −1. While the uncoated Cu-15vol.%Nb oxidized rapidly to form external Cu-oxide scales, the CuCr coating surface formed continuous Cr 2O 3 scales. With the coating, the CuNb substrate was protected from oxidation for an extended time.