Experimental study on the fretting fatigue of Inconel 718 superalloy

Fretting fatigue is a surface damage phenomenon appearing in mechanical assemblies subjected to time-varying contact forces. This type of failure is a very frequent problem in many engineering components, with special relevance in the blade-disc connections in aircraft gas turbines. In this study, different plain and fretting fatigue tests were done using different load levels and also under two different temperatures, at room temperature and high temperature (650 degrees C), in order to obtain the fretting fatigue behaviour in both conditions and compare them with that of plain fatigue test. The contact pair used to carry out these tests is the frequently used cylindrical pad pressed against a dog-bone test specimen with a rectangular cross-section. The material used to manufacture both elements is the often used Nickel alloy Inconel 718, which is widely used in the manufacture of gas turbine parts. Moreover, and because the material was received in annealed condition, this material was heat treated to improve its mechanical properties. Results of tests under different conditions are analysed and compared. Subsequently, the fracture surfaces for different specimens are analysed and fatigue crack growth rate under different testing conditions are presented and compared with data from the literature.