Spatially resolved temporal stress evolution during laser surface spot hardening of steel

The results show that inside of the martensitic transformed region (process zone) in radial and in tangential direction homogeneous compressive residual stresses are generated. The data of the in-situ diffraction experiments reveal that these compressive residual stresses develop due to (i) local compressive elasto-plastic deformations and (ii) local phase specific transformation strains. Outside the process zone, the compressive residual stresses are balanced by rather high inhomogeneous tensile residual stresses. By means of the in-situ determined diffraction data it is proven that these tensile residual stresses have their origin in the superposition of (i) quenching effects outside the process zone, (ii) local elasto-plastic deformations and (iii) the effect of phase transformations in the nearby process zone.