The effect of micro-crystallizing on the oxidation resistance of Cu–Cr alloy in air

Cu–Cr two-phase alloys (Cu–75Cr, Cu–50Cr and Cu–25Cr) at both cast and micro-crystallization states were oxidized at 800 °C in air for 50 h. Micro-crystallized Cu–Cr alloy was coated on the surface of cast Cu–Cr alloy by high frequency electro-pulse spark deposition (ESD). Oxidation kinetics results, QBSD, EDS and XRD analysis show that continuous protective oxide scales are formed on the surface of micro-crystallized Cu–75Cr and Cu–50Cr alloys while complex oxides scales are formed on the surface of cast alloys. Micro-crystallizing shortens the time to form the continuous protective scales due to the decrease of grain size and promote the outwards diffusion of Cr, thus the oxidation resistance of Cu–75Cr and Cu–50Cr alloy treated by ESD is improved. Due to the low Cr content, micro-crystallizing has no obvious contributions to the oxidation behavior of Cu–25Cr alloy. Oxidation kinetics for Cu–Cr two-phase alloys follow wn=k1twn=k1t. For both cast and ESD-treated two-phase Cu–Cr alloys, n is decreased with the decrease of Cr content.