The Fatigue Behavior of Nickel, Monel, and Selected Superalloys, Tested in Liquid Mercury and Air; A Comparison

The fatigue lifetimes and fractography were compared for nickel and typical nickel base alloys of the Monel, Inconel, and Incoloy series, tested at room temperature in alternating tension in the environments of air and liquid mercury. It was found that the fatigue life was always less in mercury and that a different fracture mode resulted. The alloys Nickel 200, Inconel 600, Incoloy 800, and Incoloy 825 that did not show intergranular fractures in the slow strain-rate tensile tests, did so under fatigue testing. A generalized crack propagation sequence in mercury was identified beginning with intergranular cracking but transferring eventually to transgranular modes.