Influence of adsorption and interfacial reactions induced by chromium and titanium on the wettability of vitreous carbon by NiPd brazing alloys

The influence of additions of chromium, titanium and CuCr on the wettability of vitreous carbon by NiPd azeotropic alloys was studied. The work was carried out at 1523 K under high vacuum by the sessile drop technique. The morphological and chemical features of the metal-carbon interface were determined by profilometry, scanning electron microscopy and microprobe analysis. Chromium and titanium active solutes lead to a decrease of more than 100° in contact angle and an order of magnitude increase in work of adhesion. These effects result from the in situ modification of both the liquid and solid sides of the interface: the formation of an adsorption layer rich in active solute on the liquid side and a metallic-like carbide on the solid side of the interface.