Abstract
To strengthen dental titanium products utilizing the solid solution hardening effect by the diffusion of interstitial alloying atoms from surface to the interior, the materials were heated at temperatures of 500〜1, 200℃ in a controlled gas atmosphere (10-5〜760 torr O2, N2, C6H6 partial pressure and vacuum). The effects of three interstitial alloying atoms, oxygen, nitrogen and carbon, were compared by measuring the micro-Vickers hardness. The distribution of Vickers hardness in the cross section of the specimen is composed of the surface hardening layer and the inner uniform hardness area. The surface hardening layer thickness experimentally obtained correlated well quantitatively with the calculated value using the activation energy of diffusion of interstitial atoms in titanium. The surface products from heat treatment were identified by X-ray diffraction. The properties of reactivity, diffusivity, solubility and the strengthening effect of the three interstitial alloying atoms were compared. Nitrogen, much less reactive than oxygen, had a solution hardening effect similar to oxygen, whereas carbon with slight solubility, easily formed a surface carbide film and had a lesser strengthening effect.
