Oxidation Behavior of Ag-20Cu-30Cr Alloy Prepared by Powder Metallurgy Method in 0.1 MPa Pure O2 at 700 and 800 °C

The oxidation behavior of Ag-20Cu-30Cr alloy prepared by powder metallurgy method was investigated in 0.1 MPa pure O2 at 700 and 800 °C. The alloy oxidation kinetics deviates from the parabolic rate law and consists of several quasi-parabolic stages with different rate constants. The alloy oxidation rate at 800 °C is bigger in the initial 4 h and afterward smaller than that at 700 °C up to 24 h. Ag-20Cu-30Cr alloy produces complex oxide scales. At 700 °C, the outer region consists of CuO layer partly covered by metal Ag, while the inner mixed oxidation region consists of alloys and oxides. With the increase of time, an irregular continuous and protective thin layer of Cr2O3 is produced at the base of oxide scales. At 800 °C, the outer region consists of CuO layer, the middle region consists of a metal Ag layer plus a mixed layer of Cu, Ag and Cr oxides or their double oxides, while the inner region consists of a regular continuous and protective thin layer of Cr2O3, which avoids the further oxidation of the alloy.