This paper discusses the results of laser peening without coating on low carbon austenitic stainless steel 316L. Unlike typical experiments on laser peening without coating (LPwC) performed with frequency doubled (green) laser and underwater irradiation, the present study reports LPwC with infrared radiation using thin layer of water as confinement medium. The dependence of laser pulse density on properties such as surface roughness, surface residual stress, microhardness, and corrosion behavior of LPwC specimen were investigated. The magnitude of surface compressive residual stress on laser peened specimen showed appreciable improvement compared to unpeened base material. Microhardness of the specimen improved by 3040% after LPwC. However, the potentiodynamic polarization study indicated that though there is an enhancement of corrosion potential (E corr), the corrosion current density (I corr) increased with increase in laser pulse density. © 2012 Elsevier Ltd.

Kalainathan S

Department of Physics

School of Advanced Sciences

Vellore Campus

Sathya Swaroop N-R

Sathyajith S

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Optics and Lasers in Engineering

The pulsating current approach in <a href="https://www.sciencedirect.com/topics/engineering/tungsten">tungsten</a> <a href="https://www.sciencedirect.com/topics/engineering/inert-gas">inert gas</a> (TIG) welding is adapted for joining <a href="https://www.sciencedirect.com/topics/engineering/hastelloy">Hastelloy</a> C-276. <a href="https://www.sciencedirect.com/topics/engineering/microstructure">Microstructure</a> examination revealed the absence of micro-segregation while employing UNS N06022 filler. Due to the prevalence of <a href="https://www.sciencedirect.com/topics/engineering/high-tensile-stress">higher tensile stresses</a> in the un-peened conditions, tensile failures were observed in the weld regions of both the joints irrespective of fillers. Low <a href="https://www.sciencedirect.com/topics/engineering/energy-engineering">energy</a> <a href="https://www.sciencedirect.com/topics/engineering/laser-shock-peening">laser shock peening</a> without coating (LSPwC) was carried out on the weld zones on both the sides of the joints with the pulse densities 2500 and 7500 pulses per cm2. This <a href="https://www.sciencedirect.com/topics/engineering/laser-surface-treatment">laser surface treatment</a> had remarkably increased the <a href="https://www.sciencedirect.com/topics/engineering/tensile-strength">tensile strength</a> of the welded joints by shifting the location of tensile failures well away from the fusion zones for all the cases. Similarly, a considerable increase is observed in the <a href="https://www.sciencedirect.com/topics/engineering/notch-toughness">notch toughness</a> of both the joints in the LSPwC condition. The enhancement in tensile strength and notch <a href="https://www.sciencedirect.com/topics/engineering/impact-toughness">impact toughness</a> of the welds could be ascribed to the <a href="https://www.sciencedirect.com/topics/engineering/compressive-residual-stress">residual compressive stresses</a> induced which were then confirmed by Sin2ψ method in <a href="https://www.sciencedirect.com/topics/engineering/x-ray-diffraction">X-ray diffraction</a> (XRD) technique.

Journal of Materials Processing Technology

Effect of low energy laser shock peening on the mechanical integrity of Hastelloy C-276 welds

The titanium alloy Ti-6Al-4V was subjected to laser peening (without coating) at power densities of 3, 6 and 9 GW cm−2. The cross sectional profiles of microhardness and residual stress indicated softening in the bulk (away from the surface) at power density of 9 GW cm−2. This behavior was analyzed using a combination of Zerilli-Armstrong phenomenological model in conjunction with the concept of adiabatic heating. The implications of this analysis was supported by structural changes in terms of α → β transition (analyzed through synchrotron radiation) and microstructural changes in terms of primary α (equiaxed) to secondary α (lamellar) transformation, which is observed for the first time here. Based on this, optimum levels of peening to improve fatigue lives are suggested through relevant experiments. © 2019 Elsevier Ltd

Optics & Laser Technology

Mechanical properties of a laser peened Ti-6Al-4V

The residual stress distribution due to laser peening without coating (LPwC) was measured by using the synchrotron radiation X-rays from BL-11 at INDUS-2, RRCAT, Indore, India. This was accomplished by using the effective and quick method of angle-dispersive X-ray diffraction (AD-XRD). LPwC was performed on the titanium TC6 and Ti-6Al-4V alloys with a laser wavelength of 1064 and 532 nm and samples were peened with three different laser power densities of 3, 6 and 9 GW cm −2 and subjected to multiple impacts (1/3/5). Followed by that, the residual stress measurements using synchrotron radiation beam energy (SRBE) of 20 and 30 keV were carried out. The results show that LPwC induces higher and deep residual stress depending upon the titanium alloy. The change of residual stress with laser power densities and impact times are calculated and discussed. Although a compressive residual stress (CRS) was observed in majority of the cases, the more detrimental tensile residual stress (TRS) was observed in few cases only, especially with the TC6 alloy. TC6 showed TRS with peening radiations of 532 nm (power density of 3 GW cm −2 ) and 1064 nm (power density of 9 GW cm −2 ). Besides, TRS was observed in multiple peened samples (5 times) at both radiations. In each of the instances the residual stress was measured at SRBE of 20 keV. It is suggested that for beneficial CRS, peening may be employed in conditions other than these. © 2019 Elsevier Ltd

Measurement

Measurement of residual stresses in titanium alloys using synchrotron radiation

Laser shock peening (LSP) is a modern and efficient thermo-mechanical approach to engineer and modify the surface and subsurface related properties of materials which has been frequently opted by contemporary researchers in the field of peening. The main objective of this review article is to emphasize LSP as a post weld treatment method which may help in the commercialization of LSP which is considered a challenge till date. Combining laser welding and laser shock peening could be an alternative and promising approach for improving weld quality over different conventional methods of post weld treatments. With this hindsight, reports incorporating welding and peening in last decades are reviewed. The notable effects of LSP on the mechanical properties and microstructure of different weldments are also discussed along with the classification and important parameters of LSP. We conclude that LSP can indeed be used as an effective post weld treatment (PWT) method in industrial manufacturing process. © 2018

Journal of Manufacturing Processes

Review: Laser shock peening as post welding treatment technique

Laser peening without coating (LPwC) was done on the titanium TC6 alloy at a wavelength of 532 nm using an Nd:YAG laser. The laser power densities of 3, 6 and 9 GW cm−2 were used to peen the samples. Samples were also peened multiple times (1, 3 and 5 passes) at 6 GW cm−2. Microhardness showed an overall 23% increase from the baseline value. Further, softening of α phase in the bulk was observed above 6 GW cm−2 in the samples peened once and above 1 pass in multiply peened samples. A similar trend was observed from the residual stress analysis of the samples. The maximum compressive residual stress was −1780 MPa at a depth of 50 μm at 9 GW cm−2. The observed softening of α phase was proposed due to adiabatic heating. Microstructural changes due to adiabatic heating resulting in increased β volume fractions were observed and confirmed by synchrotron radiation measurements. © 2017 Elsevier Ltd

Journal	Data powered by TypesetOptics and Lasers in Engineering
Publisher	Data powered by TypesetElsevier BV
ISSN	0143-8166
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