AN INVESTIGATION ON THE ADHESIVE BEHAVIOR BETWEEN TRANSITION-METALS TITANIUM, NIOBIUM, TANTALUM, AND TUNGSTEN

The contact adhesive energies between two transition metals (Nb, Ta, Ti, W) are measured in ultra-high vacuum (UHV) condition. The results show that they depend on the cohesive energies of contacted materials. It is suggested that the adhesive interaction is caused by sharing of electrons between two metals and is mainly dependent on the densities of states of their d-electrons. The value of the adhesive energies for two transition metals are in the range of 0.1 to 3.0 (eV/coupled atoms). When the samples are heated, the adhesive strength decreases drastically because of the segregations of nonmetallic impurities such as carbon, nitrogen, boron, and sulfur etc.