Surface free energy of nickel and stainless steel at temperatures above the melting point

The surface tension (liquid-state surface free energy) of pure nickel and type 304 stainless steel was measured in a narrow temperature range above the melting point by the sessile drop method. The temperature coefficients of surface free energy in the liquid state were found to be –1.76 erg cm^–2 C^–1 for nickel and –2.48 erg cm^–2 C^–1 for stainless steel. These values are shown to be a factor of 2 larger than those previously determined for the solid surface free energies of nickel and stainless steel, but have the same sign. The latent heats of fusion of nickel and 304 stainless steel were determined by comparison of variations of solid and liquid-state surface energies with temperature and found to be 292 and 284 erg cm^–2 respectively. Measurement of the contact angle for a nickel sessile drop on thoria and a stainless steel sessile drop on alumina showed a decrease in the angle with an increase in temperature.