Tribological Property of α-Pure Titanium Strengthened by Nitrogen Solid-Solution

Abstract

Mechanical and tribological properties of powder metallurgy (PM) α-titanium (Ti) materials with dissolved nitrogen atoms were evaluated in this study. Pin-on-disk wear test was carried out under dry condition, where a SKD61 disk specimen was used as a counter material. The elemental mixture of Ti and TiN powders was compacted and sintered in vacuum, and then extruded to the full-dense PM Ti rods. During sintering in vacuum, TiN particles were completely decomposed via reaction with Ti powder. Nitrogen atoms originated from TiN were dissolved into α-Ti matrix, and resulted in the remarkable improvement of micro-hardness and tensile strength. The additional heat treatment on the sintered Ti materials was effective to improve further elongation in tensile test because the localization of dissolved nitrogen atoms was decreased. The friction coefficient of nitrogen dissolved Ti material was extremely lower and more stable compared to pure Ti specimen employed as a reference material. The wear loss of the former was significantly smaller than that of the latter specimen. This is because of superior wear resistance of α-Ti material with nitrogen solid-solution due to a large increment of micro-hardness of Ti matrix.