EBSD and EDX analysis at the cladding-substrate interface of a laser clad railway wheel

Artikel i vetenskaplig tidskrift, 2006

Electron backscatter diffraction and energy-dispersive X-ray spectrometry were used to investigate the intermixed interface produced during laser cladding of a Co - Cr -Mo alloy on a steel substrate. A multi-component system and rapid solidification conditions together lead to a complex microstructure at the interface. The solidification of the cladding starts with the formation of an interface layer, which is about 75 mu m in thickness and consists of randomly oriented equiaxed grains of Co-Cr -Fe solid solution and martensite. Orientation analysis of the grains in the interface layer revealed that some grains have a special orientation relationship with the former austenite grains in the heat affected zone but the cladding is not formed by epitaxial growth on the substrate. Intermixing of the materials at the interface is providing a strong bond between the substrate and the cladding. For a grain from the interface layer to emerge as columnar grain in the cladding, it was determined that its crystallographic direction is not supposed to deviate more than 25 degrees from the sample normal direction.