Cryogenic Tensile, Fatigue, and Fracture Parameters for a Solution-Annealed 18 Percent Nickel Maraging Steel

The mechanical properties of an eighteen percent nickel, solution-annealed 300-grade maraging steel were measured to assist in the evaluation of this material for low-temperature structural applications. Tensile, fatigue-crack growth rate, and fracture toughness tests were perfromed in ambient air (295 K), liquid nitrogen (76 K), and liquid helium (4 K), with the following results: (1) the yield strength of this material increases from 831 MPa at room temperature to 1596 MP a at 4 K; (2) the tensile ductility is moderate with elongation decreasing from 15.5 to 6.7 percent for this temperature region; (3) the estimated values of fracture toughness (K_Ic) decrease from 165 MPa·m^1/2 at room temperature to 83 MPa·m^1/2 at 4 K; and (4) the fatigue-crack propagation resistance at intermediate stress intensity ranges is relatively insensitive to temperature. These results are compared with similar data for other cryogenic alloys.