Study on Bending Ultrasonic Fatigue Behavior of Sinter-hardened Fe-2Cu-2Ni-1Mo-1C Materials Prepared by Warm Compaction

摘要

Bending fatigue behavior of a sinter-hardened high density (7.4 g/cm~3) Fe-2Cu-2Ni-1Mo-lC material fabricated by die-wall lubricated warm compaction of partially-diffuse alloyed powder was studied by bending ultrasonic fatigue testing. Results showed that fatigue strength decreases continuously with the increasing number of cycles. The fatigue failure yet occurs in the regime of exceeding 10~7 cycles and exhibits no traditional horizontal plateau between 10~6 and 10~7 cycles. Fatigue strength was 194 MPa, 239 MPa and 293 MPa at 10~8, 10~7 and 10~6 cycles respectively. Scanning electron microscopy revealed that cracks initiated from large pores on the surface and from pore clusters near the sub-surface. The fatigue cracks initiated both at single and multiple sites. Crack propagation was mainly in a trans-crystalline rupture mode. Fatigue striation and cleavage plane were observed in the crack propagation region and dimples were observed in the fracture zones.