FRACTOGRAPHY OF INDUCTION-HARDENED STEEL FRACTURED IN FATIGUE AND OVERLOAD

The fracture surfaces of induction-hardened steel specimens obtained f rom an auto axle were characterized, macroscopically and microscopical ly, after being fractured in fatigue and monotonic overload. Specimens were tested in cyclic three-point bending under load control, and the S-N curve was established for specimens that had been notched by spar k machining to facilitate fractography. Scanning electron microscopy o f the fractured surfaces obtained for Lives spanning the range 17,000 to 418,000 cycles revealed diverse fracture morphologies, including in tergranular fracture and transgranular fatigue fracture. The results a re being offered to assist in the analysis of complex field failures i n strongly hardened steel. (C) Elsevier Science Inc., 1997.