Laser peening

Summary

Laser peening (LP), or laser shock peening (LSP), is a surface engineering process used to impart beneficial residual stresses in materials. The deep, high-magnitude compressive residual stresses induced by laser peening increase the resistance of materials to surface-related failures, such as fatigue, fretting fatigue, and stress corrosion cracking. Laser shock peening can also be used to strengthen thin sections, harden surfaces, shape or straighten parts (known as laser peen forming), break up hard materials, compact powdered metals and for other applications where high-pressure, short duration shock waves offer desirable processing results. History Discovery and development (1960s) Initial scientific discoveries towards modern-day laser peening began in the early 1960s as pulsed-laser technology began to proliferate around the world. In an early investigation of the laser interaction with materials by Gurgen Askaryan and E.M. Moroz, they documented pressure meas

Official source

https://en.wikipedia.org/wiki/Laser_peening

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3D laser shock peening - A new method for improving fatigue properties of selective laser melted parts

Nikola Kalentics, Christian Leinenbach, Roland Logé, Manuel Ortega Varela De Seijas

Although Selective Laser Melting (SLM) currently revolutionizes the way parts are being manufactured, certain process inherent limitations such as accumulation of residual stresses and increased porosity content can lead to a decrease in fatigue life of produced parts. 3D Laser Shock Peening is a new hybrid additive manufacturing process whereby a periodic Laser Shock Peening (LSP) treatment is added to the standard SLM process. LSP can be applied selectively in the 3D volume of metallic parts, and is shown to influence the bulk internal stress state and hardness, as well as the distribution of porosities in the material. Here, a decoupled 3D LSP process was used, i.e. LSP treatments were applied during the SLM process, by removing the sample from the SLM chamber whenever needed. We report fatigue lives of 316 L stainless steel multiplied by more than 15 times compared to standard SLM parts, and more than 57 times compared to conventional manufacturing, with a significant improvement over other state-of-the art methods. The effect of the 3D LSP treatment on SLM parts and the consequence on crack initiation and propagation is investigated by measuring the near surface residual stresses, imaging the fractured surface, measuring the porosity content and analyzing the microstructure and microhardness.

ELSEVIER2020

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Laser powder bed fusion is an additive manufacturing technique extensively used for the production of metallic components. Despite this process has reached a status at which parts are produced with mechanical properties comparable to those from conventional production, it is still prone to introduce detrimental tensile residual stresses towards the surfaces along the building direction, implying negative consequences on fatigue life and resistance to crack formations. Laser shock peening (LSP) is a promising method adopted to compensate tensile residual stresses and to introduce beneficial compressive residual stress on the treated surfaces. Using neutron Bragg edge imaging, we perform a parametric study of LSP applied to 316L steel samples produced by laser powder bed fusion additive manufacturing. We include in the study the novel 3D-LSP technique, where samples are LSP treated also during the building process, at intermediate build layers. The LSP energy and spot overlap were set to either 1.0 or 1.5 J and 40% or 80% respectively. The results support the use of 3D-LSP treatment with the higher LSP laser energy and overlap applied, which showed a relative increase of surface compressive residual stress (CRS) and CRS depth by 54% and 104% respectively, compared to the conventional LSP treatment.

NATURE PORTFOLIO2021

Healing cracks in selective laser melting by 3D laser shock peening

Andreas Burn, Hossein Ghasemi Tabasi, Jamasp Jhabvala, Nikola Kalentics, Christian Leinenbach, Roland Logé, Navid Sohrabi

Selective Laser Melting (SLM) of Ni-based superalloys such as CM247LC is prone to weld-cracking. This paper investigates how to suppress cracks by repeatedly applying Laser Shock Peening (LSP) during the building phase of SLM. Samples made of CM247LC were processed with different LSP parameters, and the influence on bulk crack density has been quantified. It was observed that for all chosen conditions, a significant decrease of up to 95% could be achieved, demonstrating the potential of the new hybrid 3D LSP method in improving SLM processability of alloys sensitive to cracking.

ELSEVIER2019