Shot peening and its influence on surface integrity of Ni-based single crystal superalloy

• Main Author: Burhanuddin Mohamed Ali
• Other Authors: Upadrasta Ramamurty
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/159082
• Institution: Nanyang Technological University

Shot peening is a well-known, reliable, and practical surface treatment process that is heavily employed in the aerospace industry to extend a component’s fatigue life and prevent premature failure. On a separate note, Ni-based single crystals have been increasingly utilised, especially so within the aerospace industry in the fabrication of engine turbine blades. This is mainly due to the absence of grain boundaries, which poses a problem at high turbine temperatures. Thereupon, the subject of shot peening of single crystals in the aerospace industry has definitely appeared more progressively over the years. Despite this, there is currently limited information about the influence of various different shot peening parameters on single crystals. This is an important topic of focus as it will help us better understand and possibly obtain the optimum set of peening parameters to be used with regards to shot peening single crystals. Therefore, this study focuses on how shot peening parameters, specifically shot peening intensity, affects the surface integrity of single crystals. Shot peening was employed to Ni-based single crystal superalloy, for the purpose of studying the impact of different peening intensities on its surface and near-surface structural evolution. The effect of the treatment on the surface roughness, surface topography, micro-hardness and crystallographic reorientation was investigated using various techniques and instrumented tests which includes 2D and 3D surface profiling, micro-hardness Vickers test and X-ray diffraction (XRD). It was observed that increasing the shot peening intensity caused higher single crystal surface roughness from 0.0597 (Ra) up to a maximum of 1.4137 (Ra). The surface depth due to deformation from shot impact also increased up to a max depth of -15 µm. Additionally, surface and sub-surface micro-hardness values increased by more than 30%. Increases in XRD peak broadening and scattering of pole figures was also observed while XRD peak intensity decreased consistently as the peening intensity increased, with a maximum of 213 in terms of decrease in XRD intensity value. Finally, FWHM values increased from 21 to 85 (FWHMx) and 30 to 65 (FWHMy) as peening intensity increased.