Investigation of contact fatigue test for laser hardened steels

Laser hardening technologies are widely used to modify the surface of steel s. Generally, the contact fatigue life of laser hardened steels are still e valuated by the conventional rolling, contact fatigue tests. However, it is found that some cracks in fatigue testing may initiate from the boundary b etween the hardened layer and the substrate. In this paper, the appropriate ness of the conventional rolling contact fatigue testing method in the lase r hardened steel test is evaluated. Experiments were done on a standard lin e contact fatigue tester with contact loads of 1800-2600 Mpa and a rotation al frequency of 2000 ipm. The location of crack initiation is examined by S EM. It is found that the contact fatigue life of laser hardened steels is i nfluenced by the depth of the hardened layer. Experimental results are comp ared with theoretical calculation. The meaning of these results is discusse d.