Meaning
High-strength alloys undergo structural degradation and subcritical crack growth under repeated cyclic loading. When subjected to millions of stress cycles, maraging steel fatigue leads to catastrophic failure if microcracks initiate at titanium nitride inclusions.
Microstructural Integrity
The lack of carbon in these alloys prevents the formation of brittle martensitic phases, which ensures high fracture toughness. The microstructural integrity relies on the uniform distribution of intermetallic precipitates during the aging heat treatment. Impurities can act as initiation sites for fatigue cracks under dynamic loads.
Fatigue Resistance
Controlled shot peening introduces compressive residual stresses that delay the initiation of surface cracks. The fatigue resistance increases when the surface is polished to eliminate machining marks and surface irregularities. Without these surface treatments, the material fails far below its nominal tensile strength under cyclic stress.
Stress Limit
Safe operations depend on keeping the applied dynamic stress below the threshold for crack propagation. This stress limit determines the maximum safe operating window for high-speed centrifuge rotors and motorsport drivetrains. If the operating stress exceeds this threshold, the component will fail rapidly because of the high crack growth rate of the alloy.
Engineers establish these thresholds through extensive spin testing of fully aged prototypes before release.
