Effects of microstructure on fretting fatigue behavior of IN100

Fretting fatigue behavior of a nickel-base superalloy, IN100, was investigated at room temperature. Two microstructures of IN100 were tested which varied primarily by the gamma grain size (3 μm versus 7 μm). Fretting fatigue tests were conducted at various stress levels using cylinder-on-flat contact configuration. An increase in the grain size was associated with decrease in the fretting fatigue strength/life of IN100. Microscopic analysis showed that the 3 μm grain microstructure provided a higher microstructural barrier to the fretting fatigue crack nucleation and initiation. On the other hand, the 7 μm grain microstructure had a higher intrinsic crack growth resistance due to the tortuous crack path requiring more energy. These features were in agreement with the plain fatigue where fine microstructures generally provide higher resistance to crack initiation but reduce crack propagation resistance while coarse microstructures have the opposite behavior.