Digital Repository, ICF12, Ottawa 2009

Font Size: 
Effect of tempering temperature on very high cycle fatigue properties of high strength steel
H. Oguma, T. Nakamura

Last modified: 2013-05-03


To investigate the effect of tempering temperature on the very high cycle fatigue
properties, uniaxial tension-compression fatigue tests of Ni-Cr-Mo steel
(SNCM439, corresponding to AISI 4340 steel) which had been tempered, either
at 433K (640Hv) or 573K (543Hv) were carried out. The fracture origins in 104 -
105 cycle range located at the specimen surface, whereas in the 105 - 108 cycle
range the fracture origins were sub-surface. The fatigue limits for the surfaceinitiated
failures were in good agreement with the conventional expression σw0 ≈
1.6·Hv. However, in the the fatigue limit in the sub-surface crack-initiation range
was lower for the harder condition. SEM examination showed that the type of
inclusion at the failure origin depended upon the tempering temperature. This
dependency may be the cause of the unusual relation between hardness and
fatigue strength in the very high cycle fatigue range.

Full Text: PDF