The paper presents a study of the surface and subsurface characteristics induced by laser peening without coating (LPwC) and dual shot peening (DSP) on the duplex aged Ti-15 V-3Al-3Cr-3Sn alloy. In 3D-optical topography analysis, DSP resulted in a six-fold enhancement in the surface roughness (Sa). Whereas, LPwC resulted in unaltered surface roughness (Sa) compared to the polished/unpeened sample. In cross-sectional microstructure studies, deformed grains and heat affected zones were observed in the near surface region of shot peened, and laser peened samples respectively. Moreover, compared to bulk hardness, shot peening and laser peening has resulted in maximum increment of ~28% and ~12% in microhardness of the near peened surface region respectively. © 2020, Springer Nature Singapore Pte Ltd.

Nageswara Rao M

Department of Manufacturing Engineering

School of Mechanical Engineering

Vellore Campus

Sathya Swaroop N-R

Department of Physics

School of Advanced Sciences

Sudhagara Rajan 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

A Comparison of Surface and Sub-surface Features Induced by Shot Peening vs. Laser Peening on a Duplex Aged Beta Ti Alloy

Lecture Notes in Mechanical Engineering Advanced Surface Enhancement

In the present study, Ti-15V-3Al-3Cr-3Sn (Ti-15-3), a beta titanium aerospace alloy in solution treated condition (850 °C/1 h) was subjected to Laser Peening without Coating (LPwC) with a wavelength of 532 nm and power density of 8.96 GW cm−2. Surface roughness was analysed using 3D optical topography. Curiously, in the near peened surface, peening induced precipitation (i.e. 19% of α precipitation) and increased fraction of low angle boundaries (∼123%) was revealed through the Electron Back Scattered Diffraction (EBSD) analysis. Through depth nanohardness measurement was carried out along the cross-section of the peened sample right from the near peened surface. Peak hardness of 4.6 GPa is observed at a depth of 100 µm from the peened surface while the base/bulk hardness of the material is 4 GPa. In addition, X-Ray Diffraction (XRD) based analysis confirmed the presence of compressive residual stress in the near surface region of the peened sample. To understand the effect of the peening induced microstructural changes and residual stresses in fatigue behaviour, staircase method of fatigue analysis was adopted and observed that the more number of run out samples belonged to laser peened condition when compared to the unpeened condition. Despite this favourable indication, fatigue limit remains more or less unaltered even after peening. Fractography studies revealed the least influence of the surface roughness induced by laser peening over the crack initiation. Irrespective of the condition (i.e. unpeened and laser peened), crack initiation was predominantly influenced by the stress concentration co-existing at the sharp corners. © 2018 Elsevier Ltd

Optics & Laser Technology

Influence of laser peening without coating on microstructure and fatigue limit of Ti-15V-3Al-3Cr-3Sn

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

Beta titanium (β-Ti) alloys have been a subject area of intense interest since 1980s. By virtue of their unique properties, β-Ti alloys very well compliment the alpha and alpha + beta alloys. Heat treatment of β-Ti alloys is the crux to their technology and application. Over the last two decades, a number of researches have been carried out on issues related to heat treatment of these alloys—sub-transus solution treatment, duplex aging and heating rate to aging temperature. Improved understanding resulting from these studies has enabled designing optimum heat treatments to achieve refined microstructures free from deleterious features with improved mechanical properties under static and dynamic loading conditions. The purpose of this overview is to take stock of progress made in recent years in understanding the heat treatment of β-Ti alloys for a better commercial exploitation. © 2016, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

Recent Developments in Heat Treatment of Beta Titanium Alloys for Aerospace Applications

In this article, an attempt has been made to investigate the effect of fillers on the pulsed current gas tungsten arc welding (PCGTAW) of Inconel 625 and Inconel 718. Two different Ni-Mo rich fillers namely ERNiCrMo-4 and ERNiCrMo-10 were employed for joining 5 mm thick plates of Ni based super alloys. The deleterious Laves phase was completely suppressed, while using these fillers. Mo rich segregation was observed in the fusion zones for both the fillers without much depletion of Mo in the fusion matrix. Tensile failures were observed at the parent metal of Inconel 718 in both the cases. It was attested from the notch tensile studies that the notch strength ratio was greater than unity, which attested that the weldments were ductile in all conditions. Impact studies showed that the weldments employing ERNiCrMo-10 exhibited better impact toughness at room temperature conditions. Hot corrosion studies were performed on the coupons exposed in the synthetic molten salt environment of 60%Na2SO4–40%V2O5 at 900 °C. Studies showed that both the parent metal Inconel 625 followed by the fusion zone of ERNiCrMo-10 exhibited better corrosion resistance in the high temperature environment. Surface analytical techniques were adopted to investigate the hot corroded species. © 2017 The Society of Manufacturing Engineers

Investigations on the microstructure, tensile strength and high temperature corrosion behaviour of Inconel 625 and Inconel 718 dissimilar joints

The goal of the present study is to investigate residual stress distributions and the accompanying deformation mechanisms during the process of laser peening without coating (LPwC), carried out on a Ti-2.5Cu alloy at a fixed power density of 6.97 GW cm− 2 with overlap rates from 50 to 90% (in steps of 10%). Thermal softening near surface (confined to a depth of 50 μm) from laser beam-material interaction was observed. Work-hardening increased with increase in overlap percentage till 80%. The maximum residual stress was found to be − 889 MPa for an optimal 70% overlap. Twinning was found to increase with the increase in overlap rates, indicating the hardening of the sample. The combined effect of adiabatic heating and thermal effects at the surface due to laser beam-material interaction (propagating inside the material), results in the softening of the material. The softening was found to be only in the onset stage, without flow localization. Softening predominates hardening beyond the overlap rates of 80% and the implications for this towards multiple peening are discussed. © 2016 Elsevier B.V.

Journal	Data powered by TypesetLecture Notes in Mechanical Engineering Advanced Surface Enhancement
Publisher	Data powered by TypesetSpringer Singapore
ISSN	2195-4356
Open Access	0