Fatigue behaviour of Co–Cr laser cladded steel plates for railway applications

In this contribution, the fatigue behaviour of steel plates cladded with Co–Cr alloys is studied. The laser cladding in two successive layers with parallel runs to cover a whole plate results in a heat affected zone of tempered martensite below the clad. The mechanical behaviour of such cladded plates is investigated in two cases with minor differences in hardness and clad thickness. The results show a very consistent and favourable fatigue behaviour of the cladded plates with limited sensitivity to these minor differences. Investigation of surface cracks of fatigue specimens revealed a well-plasticised surface with increasing number of cracks with increasing strain amplitude on the substrate side. On the clad side, shear bands could be observed, which begin to connect over grain boundaries for the higher test strain amplitudes. For all strain amplitudes, the clad and the tempered martensite layers could survive fatigue loading longer than the steel substrate layer of the composite specimens.