The Microstructure and Properties of Laser Shock Peened CMSX4 Superalloy

Abstract The influence of laser shock peening on the surface morphology and microstructure of single-crystal CMSX4 nickel-based superalloy was investigated by optical profilometry and atomic force microscopy, scanning and transmission electron microscopy as well as scanning-transmission electron microscopy in high-angle annular dark-field mode. Maps of chemical elements distribution in the laser-affected areas were determined using energy-dispersive X-ray spectroscopy. Furthermore, after the LSP, nanohardness tests were conducted on the cross section of the treated samples as well as the untreated material. Laser shock peening caused an ablation and melting of the surface layer and hence enlarged the surface roughness. Beneath the surface, in the laser shock-peened areas, severe distortion of the regular $$ {\gamma \mathord{\left/ {\vphantom {\gamma {\gamma^{\prime}}}} \right. \kern-0pt} {\gamma^{\prime}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>γ</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msup> <mml:mi>γ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:mrow> </mml:math> microstructure was observed. In the surface layer, down to about 15 μ m, shear bands of localized deformation were formed. Moreover, the result showed that the average nano-hardness value was obviously increased in the laser-treated region.