FACTORS CONTROLLING THE FATIGUE-STRENGTH OF NITRIDED TITANIUM

The factors affecting the fatigue strength of nitrided titanium were c larified. The fatigue strength depended strongly on the fracture stren gth of the compound layer formed on the surface by nitriding. We found a Hall-Petch relationship between the fatigue strength of nitrided ti tanium and the grain size. The findings indicated that the reduction i n the fatigue strength by nitriding results from both the formation of the compound layer possessing low fracture strength and grain growth occurring from ordinary nitriding. Furthermore, low-temperature nitrid ing (620 degrees C, 24 h) was proposed to suppress grain growth. This treatment method improved not only the wear resistance and the corrosi on resistance but also the fatigue strength of titanium.