Evaluation of Fracture Strength and Interfacial Strength of Titanium-Nitride Layers Formed by Gas-Nitriding of Titanium

摘要

Gas nitriding was applied to pure titanium specimens and the tensile tests were carried out on the specimens in order to evaluate the fracture strength and delamination strength of titanium nitride (TiN and Ti_2N) layers. With increasing load, both the TiN and Ti_2N layers were divided by parallel cracks repeatedly and only the TiN layer was delaminated after a large plastic deformation of substrate. The fracture strength of TiN layer was estimated by an extrapolation method from the relationship between inverse of crack intervals and nominal tensile stress. Interfacial fracture toughness between TiN and Ti_2N layers was almost independent of nitriding temperature and nitriding time, and it slightly increased with increasing thickness of TiN layer.