Characterization of Inconel 625 surface layer modified by laser shock processing

In this study the microstructure of nickel alloy (Inconel 625) surface layer after laser shock processing (LSP) was investigated by means of light microscopy, scanning electron microscopy and transmission electron microscopy. The LSP treatment was performed using a Q switched Nd:YAG laser. Optical and SEM images of the Inconel 625 after LSP showed that on the surface as well as on the cross-sections of the treated samples slip bands were clearly visible. Moreover, TEM micrographs revealed that under the thin melting layer of the treated material a high density of dislocations was present. The changes in microstructure come down even to 100 μm below the surface. The new and the most important finding of this study is that, in addition to slip bands, numerous cracks of hard carbide precipitates in the area affected by the laser process were visible both on the treated surface and on the cross-section of the material.