Measurement and analyses of molten nickel-cobalt alloy surface tension

Ni-Co super-alloy is widely used in high temperature and corrosive environments such as gas turbine engines and heat exchangers. The surface tensions of molten Ni and Ni-Co (5 and 10 mass fraction) alloys were measured at the temperature range of 1773 similar to 1873 K using an improved sessile drop method with an alumina substrate in an Ar+3%H-2 atmosphere. The surface tensions of molten Ni and Ni-Co (5 and 10 mass fraction) alloys decrease with increasing of temperature. On the basis of experimental data, the surface tension was also theoretically deduced both as functions of concentration and temperature using a model of Butler' equation. The alloy element segregation in this system was calculated. Cobalt concentration on surface of alloys is lower than that in bulk.