Influences of single laser tracks' space on the rolling fatigue contact of gray cast iron

• Discontinuous unit is fabricated on sample's surface according to bionic theory.
• The partial laser treatment reduces the tempered effect causing by overlapping.
• Materials modified with isolate units are positive to fatigue wear resistance.
• Appropriate space is adjusted to reduce the degree of non-uniform deformation.

To improve the fatigue wear resistance of gray cast iron, the surface is modified by Nd:YAG laser to imitate the unique surface of soil creatures (alternative soft and hard phases). After laser treatment, the remelting region is the named unit which is mainly characterized of compact and refinement grains. In the present work, the influence of the unit space on the fatigue wear resistance is experimentally studied. The optimum space is proven to be 2 mm according to the tested results and two kinds of delamination are observed on samples' worn surface. Subsequently, the mechanisms of fatigue wear resistance improvement are suggested: (i) for microscopic behavior, the bionic unit not only delays the initiation of microcracks, but also significantly obstructs the propagation of cracks; (ii) for macroscopic behavior, the hard phase resists the deformation and the soft phase releases the deformation.