Fractographic Features of Fatigue Fracture of 316L Steel by Additive Manufacturing

Fatigue tests and fractographic studies of specimens made of additive stainless steel 316L were carried out. The features of initiation and mechanisms of fatigue cracks growth at the stage of their stable and accelerated growth were studied; the critical lengths of cracks at on fracture surfaces corresponding to these stages were estimated. Critical stress amplitude σ* was established, upon reaching which a transition from the multi-origin fracture of the specimen at high amplitudes to predominantly single-origin fracture at low amplitudes is observed. Its accompanied by a change in the fracture mechanism, fracture surface profile, and damage to the lateral surface of specimens. It was shown that a decrease in fatigue characteristics is associated with early crack initiation on technological defects formed during the production process.