High cemperature oxidation behavior of quaternary three-phase Cu-20Ni-20Cr-5Co alloy

The oxidation of a quaternary three-phase Cu-20Ni-20Cr-5Co alloy formed by adding 5% Co(mole fraction) to Cu-20Ni-20Cr alloy was studied at 700-900 ℃ in 0.1 MPa pure oxygen.The results show that the alloy contains a mixture of three phases,and its kinetic curves deviate considerably from the parabolic rate law and are composed of a few of stages.The oxidation rates become lower evidently after 5% Co is added to Cu-20Ni-20Cr alloy.The Cu-20Ni-20Cr-5Co alloy forms the external scales containing CuO and an inner oxidation region containing a mixture of alloy and oxides.At last,this alloy is able to form a continuous layer of Cr2O3 at the top of the mixed inner region.It prevents this alloy from being oxidized further.