부산대학교 도서관

Titanium is 40% lighter than steel and is very strong in relation to its low weight, which makes it veryinteresting for lightweight applications. However, the use of titanium in certain aircraft components islimited because titanium is a relatively soft metal that quickly deteriorates when mechanically stressed.In this research, a nitriding heat treatment has been developed for Ti64 (Grade 5) alloy with the aimto improve wear properties without negative effect on fatigue and strength. The mechanical propertieswere studied through hardness and wear tests performed at room temperature in laboratory air onuntreated and treated Ti64. Different measurements techniques were used to evaluate hardness onsurface as well as polished cross-sections due to uncertainties in hardness measurements of thinfilms. The wear properties were investigated with pin-on-disc tests. The microstructures and nitridedsurfaces were also investigated by optical microscopy, scanning electron microscopy (SEM) andsurface profilometry. The analysis has shown that the nitriding process has led to the formation of anuneven compound layer and a diffusion zone beneath it. The energy dispersive X-ray spectroscopy(EDS) mapping showed a high concentration of nitrogen in the compound layer and aluminium in thediffusion zone. The microhardness measurements and nanoindentation have revealed the formationof an approximately 2.5 μm thick diffusion zone. The wear tests results showed a large difference infriction behaviour between the nitrided specimens, which has been associated with the failure of thenitrided layer and the wear rate.