Kalainathan S

Department of Physics

School of Advanced Sciences

Vellore Campus

Sathyajith S

Fulltext

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

Effect of Laser Peening without Coating on 316L austenitic stainless steel

IOP Conference Series: Materials Science and Engineering

In the present study, a binary component flux (50% SiO2 + 50% MoO3) has been used to join 6.67 mm thick plates of Nb stabilized austenitic stainless steel AISI 347, using activated flux tungsten inert gas (A-TIG) welding. Trials were performed to investigate the effect of the flux and the welding current on the depth of penetration of AISI 347. Microstructure studies revealed the formation of very fine, intimate skeletal delta ferrite along the centreline of the AISI 347 welds. It was corroborated from the tensile studies that the fracture had been experienced at the fusion zone of the ATIG weldments. The joint efficiency of ATIG welds of AISI 347 was ascertained to be 83.5% in the as-welded conditions. In the unpeened condition, the tensile stresses were predominated in the fusion zone. Low energy, double sided laser shock peening was carried out at the fusion zone of the ATIG weldments by varying pulse densities. There was a slight increment in the tensile properties, while varying the pulse densities. Furthermore, the trials were conducted by varying the number of shots for the optimal pulse density. The studies envisaged that on increasing the number of shots for a pulse density of 5000 pulses/cm2, the yield and tensile strength improve considerably by 11.8%, due to the accrued residual compressive stresses. X-ray diffraction sin2ψ method is employed to compute the residual stresses in the fusion zones to correlate the mechanical properties. It is attested from the present studies that the filler-less ATIG welding along with laser shock peening resulted in better mechanical properties. © 2017 The Society of Manufacturing Engineers

Journal of Manufacturing Processes

Effect of pulse density and the number of shots on hardness and tensile strength of laser shock peened, activated flux TIG welds of AISI 347

Laser peening without coating (LPwC) was performed on austenitic stainless steel AISI 321 with a power density of 5.97 GW cm-2 and pulse densities of 1600, 2500 and 3900 pulses cm-2. A large compressive residual stress resulted for 1600 pulses cm-2. Surface roughness was found to have increased to a relatively smaller extent with lesser number of valleys or peaks. Micro-hardness increased after the process with the depth of hardened layer extending up to 900 μm. LPwC induced martensitic phase transformation (about 18% in volume fraction) was observed near treated surface. Microstructures confirmed the phase transformation effect. The grains were not refined as a result of single LPwC scan. Thermal relaxation of residual stresses at 700 °C for 2 h were 41% in longitudinal and 140% in transverse (relative to LPwC scanning) directions. The influential factors on stress relaxation were discussed. No significant reduction in hardness was seen after thermal treatment. Followed by the thermal treatment, fully austenitic phase was recovered. © 2016 Elsevier B.V.

Surface and Coatings Technology

Laser peening without coating induced phase transformation and thermal relaxation of residual stresses in AISI 321 steel

Optics and Lasers in Engineering

Effect of laser shot peening on precipitation hardened aluminum alloy 6061-T6 using low energy laser

Overlapping rate effect on laser shock processing of 1045 steel by small spots with Nd:YAG pulsed laser

Journal of Materials Science

Influence of thermal and mechanical surface modifications induced by laser shock processing on the initiation of corrosion pits in 316L stainless steel

Materials Science and Engineering: A

Retardation of crack initiation and growth in austenitic stainless steels by laser peening without protective coating

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Open Access	Yes