Authors:
M. M. Alam
J. Powell
A. F. H. Kaplan
Department of Engineering Science and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden

J. Tuominen
P. Vuoristo
Department of Materials Science, Tampere University of Technology, FI-33101 Tampere, Finland

J. Miettinen
J. Poutala
Department of Mechanics and Design, Tampere University of Technology, FI-33101 Tampere, Finland

J. Na¨kki
Department of Materials Science, Tampere University of Technology, FI-33101 Tampere, Finland and Technology Centre KETEK Ltd, FI-67100 Kokkola, Finland

J. Junkala
T. Peltola
Technology Centre KETEK Ltd, FI-67100 Kokkola, Finland

A laser clad and machined cylindrical structural steel rod was fatigue tested under four-point bending load. The resulting fracture could be tracked back to a spherical surface pore in the Co-based coating. Due to an oxide inclusion, the pore was not identified by dye penetrant inspection. Two circular buckling strain patterns that were detected beside the pore at the surfaces after fracture confirm local plastic deformation prior to crack initiation. In order to calculate the stress field around the surface pore, linear elastic finite element analysis was carried out. For four-point bending load, a surface pore generally exceeds the maximum stress of a smooth rod as long as the pore is located within an azimuthal angle of ±55°, which was the case for the presented as well as for another pore initiated sample.