Session: Research Posters

Paper Number: 173489

Effects of Shot Peening and Laser Peening on the Microstructural, Mechanical, and Tribological Properties of Inconel 625 Superalloy 

Nickel-based superalloys such as Inconel 625 are widely used in the marine, oil and gas, aerospace, and energy industries for critical components due to their outstanding mechanical properties, including high strength, corrosion resistance, creep resistance, fatigue strength, and weldability. Despite several advantages, the alloy’s resistance to fatigue and wear can deteriorate under harsh conditions. Mechanical surface engineering techniques such as shot peening (SP) and laser peening (LP) are used to address this issue.  SP generates excessive plastic deformation near the surface and induces compressive residual stress, whereas the LP utilizes high-energy laser pulses that generate a plasma plume upon contact with the target material, resulting in a high-magnitude pressure pulse that propagates through the material. This pressure pulse generates an elastic-plastic response in the material, resulting in the introduction of high-magnitude CRSs and typically microstructural alterations near the surface. Though the effect of LP on the microstructure and mechanical properties of nickel-based superalloys has been studied extensively, the effect of LP on the microstructure and dry sliding wear behavior of Inconel 625 remains unexamined. Moreover, the direct comparison with SP has not been thoroughly investigated. This study aims to investigate the effect of LP and SP on Inconel 625, especially their microstructural and wear behavior at room temperature. To achieve this, surface topography, roughness, hardness, and dry wear tests were performed using optical microscopy, scanning electron microscopy, electron backscatter diffraction, scanning transmission electron microscopy, a microindenter, and a Rockwell hardness tester. The results demonstrate improvement in the near-surface microhardness after SP and LP.  The highest microhardness was observed in the shot-peened specimen, while laser peening showed a deeper effect, hence higher macrohardness. SP and LP increased the surface macrohardness of the specimens by ~18% and 50%, respectively. SP increased the sub-surface microhardness significantly up to 352 ± 23 HV. LP increased the microhardness, exceeding that of the untreated specimen by approximately 20 HV up to a depth of ~700 µm. Microstructural analyses revealed extensive lattice distortion and high dislocation densities near the treated surfaces, with LP inducing plastic deformation to greater depths than SP. Wear track images confirm abrasion and adhesion to be the dominant wear mechanisms for all specimens. While no noticeable change in the coefficient of friction was observed for all specimens, notable decreases in the wear rate were observed following laser peening and shot peening, with the laser peened specimen exhibiting the best resistance to wear. These findings provide valuable quantitative and qualitative comparisons of the effects of laser peening and shot peening on Inconel 625, enhancing the understanding of the underlying mechanisms that drive the observed microstructural and mechanical improvements. 

Presenting Author: Md Shaheen Mahmood George Mason University

Presenting Author Biography: Md. Shaheen Mahmood is a Ph.D. candidate in the Department of Mechanical Engineering at George Mason University. He earned his Bachelor’s degree in Mechanical Engineering from the Bangladesh University of Engineering and Technology (BUET) in 2012. Prior to beginning his doctoral studies in 2022, he worked for over seven years at the largest power generation company in Bangladesh. His current research focuses on contact mechanics and tribology, with an emphasis on surface interactions and material behavior under critical conditions.

Authors:

Md Shaheen Mahmood George Mason University
Nicholas Brooks University of Alabama
Noah Holtham University of Alabama
Russell Rowe University of Alabama
Lloyd Hackel Curtiss-Wright Surface Technologies
Keivan Davami University of Alabama
Ali Beheshti George Mason University