Residual stress analysis in Co-based laser clad layers by laboratory X-rays and synchrotron diffraction techniques

Thick Co-based coatings were prepared by laser cladding technique on C45 steel substrates with different geometries. Microstructural observations were realized using optical, scanning electron and orientation imaging microscopy. The residual strain state on the surface of a clad layer was determined by the sin2Ψ-technique using laboratory X-rays. The diffraction of synchrotron radiation in θ–2θ was used to acquire information from the bulk of the materials. Internal stress was characterized through the depth and width of the coatings. Elastic moduli required for stress state calculation were measured by the nanoindentation technique and also estimated from moduli of γ-Co single crystal. A misorientation between principal strain direction and cladding direction was observed on the surface of Stellite 20 coating. The stress profiles inside clad layers reveal the influence of scanning speed, clad layer shape, laser tracks overlap and stress release component due to cross-sectioning. The strong texture inside the coatings affects diffraction conditions, the precision of the measurements and also ability to collect experimental data.