Surface Integrity of additively manufactured Inconel-718 by peening approaches

ABSTRACT

In this study, laser powder bed fused (LPBF) Inconel 718 alloy coupons are exposed to laser shock peening and shot peening to evaluate the post-treatment effect on mechanical performance. The coupons are analyzed under different conditions, such as As-built, heat-treated, shot-peened, and Laser shock peening (LSP) with overlapping percentages of 60, 70, and 80. The micrograph of the As-built IN718 sample surface shows the presence of unfused powder and tiny pores with precipitation, the laser-peened sample exhibits the refinement of the grains, while the shot-peened sample exhibits defect-free surface with waviness where the X-ray Diffraction (XRD) peaks ensure the quantitative agreement in each stage of the peening process. The microhardness was increased by 102.87% after LSP with 80% overlap, and by 71.96% after shot peening. The compressive residual stress was enhanced 2.39 times after shot peening and 1.78 times after LSP-80% when compared to the as-built coupon. This study has shown the elimination of the tensile residual stress, increment of microhardness, improvement of surface morphology in Laser powder bed fused material through LSP, and shot peening of IN718 alloy.

KEYWORDS:

• LPBF
• Inconel 718 alloy
• laser shock peening
• shot peening
• residual stress
• SEM
• XRD

Acknowledgment

The authors thank VIT University for providing the facilities to carry out the research and extend their thanks to Rapid DMLS, Bangalore, for manufacturing the specimens. The authors also thank Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore for their timely help in utilizing the Talysurf CCI 3D non-contact type surface profilometer.

Disclosure statement

No potential conflict of interest was reported by the author(s).