Effect of Post Laser Shock Peening on Microstructure and Mechanical Properties of Inconel 718 by Selective Laser Melting

2019 ◽  
Author(s):  
Kuldeep Singh Sidhu ◽  
Yachao Wang ◽  
Jing Shi ◽  
Vijay K. Vasudevan ◽  
Seetha Ramaiah Mannava
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Inconel 718 ◽  
Compressive Residual Stress ◽  
High Energy ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Laser Melting ◽  
Heat Treated ◽  
Shock Peening

Abstract This study investigates the effects of laser shock peening (LSP) on residual stress, near surface modification, and hardness of Inconel 718 (IN718) specimens manufactured by selective laser melting (SLM) technique. Optical microscope and electron backscattered diffraction (EBSD) is used to characterize the microstructures of both heat-treated and as-built specimens. A nanoindentation test is performed to determine the properties such as the hardness of as-built and heat-treated specimens. Afterward, the hardness along the distance from the LSP treated surface is also defined. To investigate the effect of LSP energy on the mechanical properties of specimens, two levels of LSP energy, e.g., low energy LSP (6.37 GW/cm2) and high energy LSP (8.60 GW/cm2), are carried out on selected samples. With the increase in laser energy density, it is found that both compressive residual stress and hardness increase after LSP treatment. The as-built specimens after high energy LSP treatment show the compressive residual stress of −875 MPa, and the surface hardness increases from 468 HV to 853 HV.

scholarly journals Effects of Laser Shock Peening on Microstructure and Properties of Ti–6Al–4V Titanium Alloy Fabricated via Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3261
Author(s):  
Liang Lan ◽  
Ruyi Xin ◽  
Xinyuan Jin ◽  
Shuang Gao ◽  
Bo He ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Titanium Alloy ◽  
Grain Refinement ◽  
Selective Laser Melting ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Laser Melting ◽  
Α Phase ◽  
Shock Peening

Laser shock peening (LSP) is an innovative surface treatment process with the potential to change surface microstructure and improve mechanical properties of additively manufactured (AM) parts. In this paper, the influences of LSP on the microstructure and properties of Ti–6Al–4V (Ti64) titanium alloy fabricated via selective laser melting (SLM), as an attractive AM method, were investigated. The microstructural evolution, residual stress distribution and mechanical properties of SLM-built Ti64 samples were characterized before and after LSP. Results show that the SLM sample was composed of single hcp α’ phase, which deviates from equilibrium microstructure at room temperature: α + β phases. The LSP significantly refines the grains of α’ phase and produces compressive residual stress (CRS) of maximum magnitude up to −180 MPa with a depth of 250 μm. Grain refinement of α’ phase is attributed to the complex interaction of dislocations and the intersection of deformation twinning subjected to LSP treatment. The main mechanism of strength and micro-hardness enhancement via LSP is ascribed to the effects of CRS and α’ phase grain refinement.

Massive Parallel Laser Shock Peening: Simulation, Verification, and Analysis

2005 ◽  
Author(s):  
A. W. Warren ◽  
Y. B. Guo ◽  
S. C. Chen
Keyword(s):  
Residual Stress ◽  
Surface Integrity ◽  
Compressive Residual Stress ◽  
Laser Intensity ◽  
Shock Pressure ◽  
Laser Shock Peening ◽  
Massively Parallel ◽  
Laser Shock ◽  
Laser Material ◽  
Shock Peening

Laser shock peening (LSP) is a surface treatment process to improve the surface integrity of metallic components. The nearly pure mechanical process of LSP results in favorable surface integrity such as compressive residual stress and improved surface material properties. Since LSP is a transient process with laser pulse duration time on the order of 40 ns, real time in-situ measurement of laser/material interaction is very challenging, if not impossible. A fundamental understanding of laser/material interactions is essential for LSP planning. Previous finite element simulations of LSP have been limited to a single laser shock location for both two and three dimensional modeling. However, actual LSP are performed in a massively parallel mode which involves almost simultaneous multi-laser/material interactions in order to induce uniform compressive residual stress across the entire surface of the workpiece. The massively parallel laser/material interactions have a significant compound/interfering effect on the resulting surface integrity of the workpiece. The numerical simulation of shock pressure as a function of time and space during LSP is another critical problem. The purpose of this paper is to investigate the effects of parallel multiple laser/material interactions on the stress/strain distributions in the workpiece during LSP of AISI 52100 steel. FEA simulations of LSP in single and multiple passes were performed with the developed spatial and temporal shock pressure model via a subroutine. The simulated residual stresses agree with the measured data in nature and trend, while magnitude can be influenced by the interactions between neighboring peening zones and the locations of residual stress measurement. Design-of-experiment (DOE) based simulations of massive parallel LSP were also performed to determine the effects of laser intensity, laser spot size, and peening spacing on stresses and strains. Increasing the laser intensity increases both the stress magnitude and affected depth. The use of smaller laser spot sizes decreases the largest magnitude of residual stress and also decreases the depth affected by LSP. Larger spot sizes have less energy attenuation and cause more plastic deformation. Spacing between peening zones is critical for the uniformity of mechanical properties across the surface. The greatest uniformity and largest stress magnitudes are achieved by overlapping of the laser spots.

Study on Strengthening Mechanism of Microscale Laser Shock Peening

2010 ◽  
Vol 431-432 ◽  
pp. 221-224
Author(s):  
Yu Jie Fan ◽  
Jian Zhong Zhou ◽  
Shu Huang ◽  
Min Wang ◽  
Yin Bo Zhu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Energy ◽  
Grain Boundary ◽  
Compressive Residual Stress ◽  
Influence Factors ◽  
Strengthening Mechanism ◽  
Point Of View ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Shock Peening

Microscale laser shock peening (μLSP) is a novel surface treating technology which oriented to microscale metal components in MEMS. Beneficial compressive residual stress is induced at the shocked region to improve the performance of microstructure based on wave-solid interactions. In this paper, the basic principle of μLSP and mechanism of wave-solid coupling were introduced, the influence factors on strengthening effects, such as micro-size effect, anisotropy, dislocation, stacking fault, grain boundary and surface energy were discussed from the microscopic point of view, the results provide theoretical guidance for further study.

scholarly journals A parametric neutron Bragg edge imaging study of additively manufactured samples treated by laser shock peening

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Matteo Busi ◽  
Nikola Kalentics ◽  
Manuel Morgano ◽  
Seth Griffiths ◽  
Anton S. Tremsin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Compressive Residual Stress ◽  
Laser Shock Peening ◽  
Powder Bed Fusion ◽  
Laser Shock ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Shock Peening

AbstractLaser 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.

Prediction of Residual Stress Random Fields for Selective Laser Melted A357 Aluminum Alloy Subjected to Laser Shock Peening

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Mohammad I. Hatamleh ◽  
Jagannathan Mahadevan ◽  
Arif Malik ◽  
Dong Qian ◽  
Radovan Kovacevic
Keyword(s):  
Residual Stress ◽  
Random Fields ◽  
Joint Probability ◽  
High Energy ◽  
Laser Shock Peening ◽  
Model Parameters ◽  
Laser Shock ◽  
Near Surface ◽  
Numerical Predictions ◽  
Shock Peening

Abstract Residual stress (RS) is a major processing issue for selective laser melting (SLM) of metal alloys. Postprocessing by way of heat treatment or hot isostatic pressing is usually required for acceptable mechanical properties. In this work, laser shock peening (LSP) treatment on both SLM and cast aluminum A357 alloys are compared with regard to the development of beneficial near-surface compressive RS. Experiments are conducted using high energy nanosecond pulsed laser, together with a fast photodetector connected to a high-resolution oscilloscope and high-speed camera to identify detailed temporal and spatial laser pulse profiles to improve numerical predictions. Constitutive modeling for SLM A357 alloy is performed using finite element simulation and data obtained from X-ray diffraction (XRD) measurements. Since XRD-RS measurements are accompanied with significant machine-reported error, an effective method is introduced to quantify the material constitutive model uncertainty in terms of a joint probability mass function. Conventionally, most constitutive behavior research for LSP involves deterministic material modeling. Predicted RS using deterministic approaches fail to reflect real-world variations in the materials, laser treatment, or RS measurements. A discretized Bayesian inference is used to quantify the rate-dependent plasticity material model parameters as a joint probability function. RS are then characterized as random fields, which provides far greater insight into the practical ability to attain desired residual stresses. Moreover, for identical LSP treatments, it is determined that the material models are significantly different for the SLM and the conventional cast A357 aluminum alloys, resulting in much lower magnitude of compressive RS in the SLM alloy.

Plastic Deformation in Silicon Crystal Induced by Heat-Assisted Laser Shock Peening

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Gary J. Cheng ◽  
M. Cai ◽  
Daniel Pirzada ◽  
Maxime J.-F. Guinel ◽  
M. Grant Norton
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Compressive Residual Stress ◽  
Silicon Crystal ◽  
Brittle Materials ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Electron Backscattered Diffraction ◽  
Transmission Electron ◽  
Shock Peening

The response of solid to shock compression has been an interesting topic for more than a century. The present work is the first attempt to experimentally show that plastic deformation can be generated in brittle materials by a heat-assisted laser shock peening process, using silicon crystal as a sample material. Strong dislocation activity and large compressive residual stress are induced by this process. The dislocation structure is characterized with transmission electron microscopy and electron backscattered diffraction. The residual stress is measured using Raman scattering. This work presents a fundamental base for the application of laser shock peening in brittle materials to generate large compressive residual stress and plastic deformation for better mechanical properties, such as fatigue life and fracture toughness.

Fabrication and Finite Element Simulation of Sequential Laser Shock Peening of Biodegradable Mg-Ca Implants

2009 ◽  
Author(s):  
M. P. Sealy ◽  
Y. B. Guo ◽  
M. Salahshoor ◽  
R. Caslaru
Keyword(s):  
Residual Stress ◽  
Compressive Residual Stress ◽  
Bone Growth ◽  
Internal State ◽  
Treatment Method ◽  
The Body ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Negative Effect ◽  
Shock Peening

Current biocompatible metals such as steel and titanium alloys have excellent corrosive properties and superior strengths. However, their strengths are often too high and as a result have a negative effect on the body. Therefore, Magnesium (Mg) alloys with relatively low strengths are ideal biocompatible metallic materials. The problem with Mg implants is how to control corrosion rates so that the degradation of Mg implants may match with bone growth. The high compressive residual stress induced by laser shock peening (LSP) has a great potential to slow down the corrosion rate. LSP is a known surface treatment method to impart compressive residual stress in subsurface of a metal. Therefore, LSP was initiated in this study to investigate surface topography and integrity produced by peening a Mg alloy. A 3D semi-infinite simulation has also been developed to predict the topography and residual stress fields produced by sequential peening. The dynamic mechanical behavior was modeled using a user material subroutine of the internal state variable plasticity model. The temporal and spatial peening pressure was modeled using a user load subroutine. The simulated dent agrees with the measured dent topography in terms of profile and depth. Sequential peening was found to increase the tensile pile up region which is critical to tribological applications. The predicted residual stress profiles are also presented.

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