Thermochemistry of Sapphire Wetting by Steel Containing Both Aluminum and Titanium in Nitrogen Atmospheres

A modified sessile drop technique was used to investigate the wetting of steels containing aluminum and/or titanium as a function of furnace atmosphere. It was found that the steel chemistry and furnace atmosphere had little effect on wetting except in the case of a particular ultra-low carbon steel containing both aluminum and titanium. This steel was found to show significantly lower contact angles than any other steel tested when it was in an atmosphere of pure hydrogen. as nitrogen was added to the atmosphere, the contact angle increased monotonically and irreversibly. the interaction between aluminum, titanium, and nitrogen is explained in terms of first-order interaction coefficients available in thermodynamic literature.