INFLUENCE OF CRYSTAL ORIENTATION ON CYCLIC SLIDING FRICTION AND FRETTING FATIGUE BEHAVIOR OF SINGLE CRYSTAL Ni-BASE SUPERALLOYS

摘要

The influence of the crystallographic orientation of single crystal (SC) Ni-base superalloys on the cyclic sliding friction (CSF) properties and the fretting fatigue failure was studied under ambient and high temperature conditions. A major emphasis was placed on studying the influence of the crystal orientation of the SC alloy with respect to normal load/contact pressure direction as well as with respect to frictional force/fretting direction. While the influence of contact plane on the coefficient of friction was found to be definite, a significant effect of sliding orientation on the frictional behavior was also observed. Anisotropic behavior of particular importance was found in the fretting fatigue tests. Here the life was reduced significantly compared with that of plain fatigue, and notable differences in crack initiation and growth for different secondary crystallographic orientations of contact pressure direction were identified. A mechanism-based numerical model was proposed by employing the Hertzian and Boussinesq-Cerruti analyses to provide some reasonable explanations on the above experimental results.