Operational characteristics and power scaling of a transverse flow transversely excited CW CO2 laser

Khare, Jai; Sreedhar, R.; Paul, C. P.; Reghu, T.; Nath, Ashish Kumar

doi:10.1007/bf02705072

Cited by 17 publications

(7 citation statements)

References 12 publications

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“…Laser surface treatment (LST) experiments were performed on AISI 1040 steel specimens (3063065 mm) in normalised condition with a 2?5 kW continuous wave CO 2 laser. 17,18 The specimens exhibited typical ferrite pearlite microstructure with microhardness of 250-280 HV (200 g). Chemical composition (in wt-%) of the substrate was as follows: Fe-0?38C-0?2Si-0?7Mn-0?05P-0?04S.…”

Section: Methodsmentioning

confidence: 99%

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Microstructural characterisation of laser surface treated AISI 1040 steel with portable X-ray stress analyzer

Ganesh

Kumar

Kaul

et al. 2013

Surface Engineering

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An experimental study was performed for non-destructive microstructural characterisation of laser surface treated AISI 1040 steel specimens with a portable X-ray diffraction based residual stress analysis system. Laser treated specimens were characterised by residual stress and (211) ferrite peak width measurements, and results were compared with those obtained by optical microscopy. The techniques were sensitive enough to distinguish four different cases arising during laser surface treatment, namely, no transformation hardening, insufficient hardening, adequate transformation hardening and surface melting. On the laser treated surface, the extents of laser melted zone and various microstructural zones of solid state transformation hardened region could be clearly identified. Although both the techniques provided fair estimate of total width of laser treated region, ferrite peak width is a more sensitive parameter to record microstructural transitions involving change in tetragonality of martensite. The technique has a potential for in situ microstructural analysis of ferritic steel weldments.

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Section: Methodsmentioning

confidence: 99%

“…17,18 The specimens exhibited typical ferrite pearlite microstructure with microhardness of 250-280 HV (200 g). Chemical composition (in wt-%) of the substrate was as follows: Fe-0?38C-0?2Si-0?7Mn-0?05P-0?04S.…”

Section: Methodsmentioning

confidence: 99%

Microstructural characterisation of laser surface treated AISI 1040 steel with portable X-ray stress analyzer

Ganesh

Kumar

Kaul

et al. 2013

Surface Engineering

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“…Laser surface melting experiments were conducted in three sets. First set of experiment was conducted with pulsed 150 W average power Nd:YAG laser while subsequent sets of experiments were performed with indigenously developed 10 kW CO 2 laser [18][19][20] in continuous wave and pulse modulated modes respectively. Table 2 summarises experimental laser surface melting parameters.…”

Section: Laser Surface Meltingmentioning

confidence: 99%

Novel laser surface treatment approach to suppress sensitisation in modified type 316(N) stainless steel weld metal

Parvathavarthini¹,

Dayal²,

Kaul³

et al. 2008

Science and Technology of Welding and Joining

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Welded components are subjected to solution annealing heat treatment for achieving full stress relief and restoration of mechanical properties and corrosion resistance. During such heat treatments, optimum cooling rate has to be selected because very slow cooling rate will result in sensitisation and susceptibility to intergranular corrosion whereas fast cooling will result in reintroduction of residual stress. For 316 LN stainless steel which is welded using modified E316-15 electrodes (0?045-0?055%C), critical cooling rate above which there is no risk of sensitisation is 75 K h 21 . This paper presents a novel laser surface treatment which suppresses sensitisation in weld metal, even at a slower cooling rate of 65 K h 21 . Experiments involving laser surface melting were carried out with 150 W average power pulsed Nd:YAG laser and 10 kW CO 2 laser, in both continuous wave and pulse modulated (100 Hz) modes. Best results were obtained when surface melting was performed with high frequency pulse modulated CO 2 laser beam. The processed weld metal remained unsensitised after solution annealing followed by slower rate of cooling at 65 K h 21 . Numerical simulation study was performed with ANSYS 7?0 software to understand the physical reason behind the difference in sensitisation behaviour of CO 2 laser melted specimens under continuous wave and high frequency pulse modulated conditions and the predictions were validated using results of electron backscattered diffraction studies. Weld metal specimens treated with high frequency pulse modulated CO 2 laser clearly showed evolution of fine grains near the fusion boundary region which enhanced sensitisation resistance.

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“…Laser welding experiments were performed with an indigenously developed 10 kW continuous wave CO 2 laser. 23 Laser welding experimental set-up consisted of laser system, integrated with a beam delivery system and a computer controlled 3 axis workstation. Laser beam, emanating out of the laser system, was folded with a 45u plane gold coated copper mirror and subsequently focused with a 127 mm focal length planoconvex ZnSe lens, housed in a water cooled copper nozzle.…”

Section: Experimental Experimental Set-upmentioning

confidence: 99%

Effect of active flux addition on laser welding of austenitic stainless steel

Kaul¹,

Ganesh²,

Singh³

et al. 2007

Science and Technology of Welding and Joining

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The use of active flux in tungsten inert gas (TIG) welding is known to increase its weld depth. The present paper involves study of active flux laser beam welding (ALBW) of austenitic stainless steel sheets with respect to its effect on plasma plume, microstructure and mechanical properties of the resultant weldments. ALBW performed with SiO 2 as the flux significantly modified shape of the fusion zone (FZ) to produce narrower and deeper welds. Plasma plume associated with the process was considerably smaller and of lower intensity than that produced during bead on plate laser beam welding (LBW). Flux addition during LBW produced thin and rough weld bead associated with humping. The development of such a weld bead is cause by reversal in the direction of Marangoni flow by oxygen induced inversion of surface tension gradient, widely fluctuating plasma plume and presence of oxides on the weld pool surface preventing free flow of the melt. Active flux laser weldments exhibited lower ductility than that of bead on plate laser weldments.

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Operational characteristics and power scaling of a transverse flow transversely excited CW CO2 laser

Cited by 17 publications

References 12 publications

Microstructural characterisation of laser surface treated AISI 1040 steel with portable X-ray stress analyzer

Microstructural characterisation of laser surface treated AISI 1040 steel with portable X-ray stress analyzer

Novel laser surface treatment approach to suppress sensitisation in modified type 316(N) stainless steel weld metal

Effect of active flux addition on laser welding of austenitic stainless steel

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