Abstract
Fatigue tests of W–Mo type high-speed steel specimens were carried out at 20 and 600°C under various stress amplitudes σ. Fatigue lives of the specimens tested at 20 and 600°C under each amplitude between 1100 and 1400 MPa were identical, but under each amplitude between 700 and 1000 MPa, those of the specimens tested at 600°C were shorter than those at 20°C. Fracture origins of the specimens fatigued at 20°C under all stress amplitudes and at 600°C under σ≧1100 MPa were large aggregates of 10~13 μm, comprising two or three M6C·MC carbides, and those tested at 600°C under σ≦1000 MPa were large isolated M6C·MC carbides of about 8 μm. When fatigued at 20°C under all stress amplitudes and at 600°C under σ≧1100 MPa, a crack propagated between two voids, produced by decohesion of the M6C/MC interfaces, in adjacent large two M6C·MC carbides which constitute a carbide aggregate, whereas in the specimens tested at 600°C under σ≦1000 MPa, cracking was initiated from the voids in large isolated M6C·MC carbides of about 8 μm. The fatigue lives of the specimens tested at 600°C under σ≦1000 MPa are shorter because the nucleation of cracks from isolated M6C·MC carbides occurs more rapidly than that of cracks in large M6C·MC carbide aggregates.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have