Ultra-high cycle fatigue behavior of a novel 1.9 GPa grade super-high-strength maraging stainless steel

Abstract Super-high-strength maraging stainless steel (MSS) is of great interest for the next generation aircraft. The ultrasonic fatigue behavior was studied for a 1.9 GPa grade ultra-high-strength MSS with a composition of 13Co-13Cr-3.5Mo-4.5Ni-0.5Ti (at. %). The ultra-high cycle fatigue limit was 560 MPa. Cracking initiated on the surface or at non-inclusion interior sites. A crack initiation and propagation model was proposed through a discussion of the fracture mechanism: (i) the surface defect-induced failure was caused by machining marks with a critical size of 0.6 μm; and (ii) the interior matrix induced failure was caused by a defect larger than 3.3 μm. The fatigue number ( N f ) of the surface induced failures ranged from 6 × 10 4 to 1.4 × 10 5 , while that of the interior induced failures was much longer, ranging from 8.6 × 10 6 to 3.2 × 10 8 .