Research on Rotating Bending Fatigue Property of a Novel Nickel-Based Non-magnetic Bearing Alloy

A nickel-based non-magnetic bearing alloy GNiCr40Al3Ti produced by vacuum induction melting was studied in this research. After solid solution treated at 1200 °C and aged at 600 °C, five stress levels of 1020, 1040, 1060, 1080, and 1100 MPa were conducted for rotating bending fatigue tests. The fatigue fracture surface is mainly composed of crack initiation source, crack propagation zone, and instantaneous break zone. Based on the linear model, the S–N curve was obtained, and the median fatigue limit is calculated to be 945 MPa. In the microstructure, a large number of α-Cr precipitates at grain boundaries, exerting a pinning effect, which suppresses the growth of grain size, but on the other hand, it also becomes a source of fatigue cracking which causes the fatigue fracture. However, non-metallic inclusions mainly composed of nitrides are distributed in the form of fine dispersion and have not become the main factor of fatigue failure. It can be indicated from the results that obtaining higher level of refinement and homogenization distribution of the second phase in microstructure and segregation of large particles of α-Cr is a key measure to further improve the rotating bending fatigue strength of GNiCr40Al3Ti.