1995 Volume 81 Issue 6 Pages 661-666
Effects of atmosphere and strain amplitude on low cycle fatigue behavior of SKD6 hot work tool steel were investigated. The fatigue life in vacuum was twice as long as that in air. It became clear from the results obtained from the experiment conducted in vacuum that slip bands on the specimen surface were formed during fatigue and grew up with increasing number of cycles. The initial fatigue cracks were generated at the intersections of slip bands and were vertical to loading direction. The fatigue cracks mainly initiated at internal inclusions when tested in vacuum, whereas superficial cracks were observed on the same fracture surface when applied higher strain amplitude. In contrast, nucleation sites of fatigue crack when tested in air were specimen surface irrespective of the magnitude of strain amplitude. The improvement of low cycle fatigue properties in vacuum was mainly due to the decreasing of growth rate of superficial and internal cracks to the critical crack length.
