Crack Growth Resistance of Laser Surface Remelted Nodular Cast Iron

Abstract The laser surface remelting (LSR) process is applied to modify the surface properties of nodular cast iron and is suitable for manufacture of various machine and tool parts. Usually, studies of surface remelted layers include microstructural and microchemical analyses, measurements of residual stresses, and various wear and corrosion tests. This paper will represent microstructural and microhardness analyses of the thin surface layer after laser remelting of nodular cast iron 500-7. Particular attention is paid to fatigue crack initiation and propagation tests. Crack initiation and growth behavior was assessed under bending test conditions. The comparison is made between as-received nodular cast iron 500-7 and the same material, where one of the surfaces is altered with the LSR process. As the crack propagation is perpendicular to the laser remelted layer, the specimens with a thin laser surface remelted layer exhibited higher resistance to fatigue crack growth in the low stress intensity factor range ΔKth than as-received nodular cast iron specimens. Also, ΔKIC is higher in the case of the laser remelted surface.