Investigation on keyhole mode fiber laser welding of SS 316 in a self-protected atmosphere

Chowdhury, Sohini; Nirsanametla, Yadaiah; Muralidhar, M.

doi:10.1177/0954406219864137

Cited by 5 publications

(4 citation statements)

References 31 publications

(37 reference statements)

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“…A similar enhanced weld bead was revealed on 316 austenitic stainless steel welded joint through the LBW process. 24 The microstructure of base metal revealed complete austenite morphology with randomly presented annealing twins (Figure 2(b)). The average size of the grains at the base metal was recorded around 54 µm.…”

Section: Resultsmentioning

confidence: 99%

Probing the stress corrosion cracking resistance of laser beam welded AISI 316LN austenitic stainless steel

Rajasekaran

Lakshminarayanan

2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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The stress corrosion cracking (SCC) resistance of the laser beam welded (LBW) AISI 316LN austenitic stainless steel (SS) was assessed and compared to the base metal (BM). The weld joint was produced using a 2.5 kW laser power source at 1500 mm/min welding speed. Microstructural characterization of the base metal and weld joint were done by the following techniques: (i) Optical Microscopy (OM), (ii) Scanning Electron Microscopy (SEM) and (iii) Transmission Electron Microscopy (TEM). The primary mechanical properties such as strength, toughness and hardness of the welded joint were evaluated and compared with the base metal. Stress Corrosion Cracking (SCC) assessment was done in boiling 45 wt% MgCl2 solution at constant load condition as per American Society for Testing and Materials (ASTM) standard G36-94. From the SCC experiment data, steady-state elongation rate ([Formula: see text]), transition time ([Formula: see text]) and time to failure ([Formula: see text]) were found and generalized equations to predict the time to failure of the base metal and LBW joint were successfully derived. The passive film rupture mechanism majorly influenced the SCC failure for 316LN and welded joint. The formation of the discontinuous δ-ferrite network, residual stress and nitrogen pore nucleation at the fusion zone of the LBW joint deteriorated the SCC resistance. The metallographic and fractographic studies revealed brittle transgranular SCC failure of the base metal as well as the LBW joint in all the stress conditions.

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Section: Resultsmentioning

confidence: 99%

Probing the stress corrosion cracking resistance of laser beam welded AISI 316LN austenitic stainless steel

Rajasekaran

Lakshminarayanan

2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…This approach is often matched with the assumption of a rotational keyhole symmetry [24][25][26][27], which generally makes the modeling suitable only for low welding speeds. Instead, the keyhole shape modeling for higher welding speeds, which are much more commonly employed in manufacturing processes, needs the consideration of an asymmetric profile which could be achieved differentiating the balance calculations at the front keyhole wall (i.e., the half of the liquid-vapor interface which precedes the laser beam) from those at the rear keyhole wall (i.e., the other half which follows the laser beam) [7,[28][29][30][31][32][33][34][35]. All the applications of the asymmetric keyhole model consider the plasma absorption through inverse Bremsstrahlung assuming a constant value of the related absorption coefficient, which is temperature-dependent.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on the Influence of the Plasma Properties on the Keyhole Geometry in Laser Beam Welding

2022

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Keyhole laser welding is the benchmark for deep-penetration joining processes. It needs high incident laser beam power densities at the workpiece surface to take place. The gaseous phase plays a fundamental role to keep the deep and narrow keyhole cavity open during the process. The plasma created in this process is a mixture of ionized metal vapors and the environmental gas and it develops inside the keyhole (keyhole plasma) and above the workpiece surface (plasma plume). The presence of plasma implicates absorption, scattering, and refraction of laser beam rays. These phenomena alter the power density of the laser beam irradiating the workpiece surface and thus affect the resulting welding process. In this work, a mathematical and numerical model has been developed to calculate the keyhole shape taking into account the plasma absorption effects. The model considers the keyhole walls as the liquid-vapor interface and computes the keyhole geometry applying a local energy balance at this interface. In addition, the model takes into account the multiple reflections effects inside the cavity through an iterative ray-tracing technique, and calculates the absorption mechanism due to inverse Bremsstrahlung for each ray along its segmented path inside the keyhole. Results show the effect of plasma properties on the keyhole shape and depth.

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“…9 HEDW process has some notable advantages over conventional arc welding processes such as (i) Increased weld penetration depth (ii) Capable of producing the weld at high speeds (iii) Producing narrow weld metal and small heat-affected zones (HAZ's). 10 Compared to the EBW process, LBW can be utilized at various atmospheres and in the difficult approach areas of the nuclear reactors. Serizawa et al 11 reported that in the F82H-SUS316L dissimilar combination, the weld metal phases are changed from martensite to austenite by shifting the beam positions.…”

Section: Introductionmentioning

confidence: 99%

Decisive impact of Filler-free joining processes on the Microstructural evolution, tensile and impact properties of 9Cr-1Mo-V-Nb to 316 L(N) dissimilar joints

Venkatakrishna

Lakshminarayanan

Vasantharaja

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part C:

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Filler-free (FF) welding processes namely, Activated Tungsten Inert Gas welding (ATIG), Laser Beam Welding (LBW), and Friction Stir Welding (FSW) were utilized for joining the nuclear grade 9Cr-1Mo-V-Nb ferritic-martensitic steel and 316 L(N) austenitic stainless steel. A comparative investigation was made by assessing the weld geometries, metallurgical features, material mixing proportions, carbon diffusion behaviour, and mechanical properties of the post-weld heat-treated (PWHT) dissimilar weld joints. Geometries of the weld zones were observed with the transverse and longitudinal macrographs. Metallurgical features were examined by optical microscopy (OM) and Scanning electron microscopy (SEM). Three-phase microstructures were identified in the dissimilar weld zones (DWZ). The elemental distributions were identified by Energy-dispersive X-ray spectroscopy (EDAX). The mixing proportions of the dissimilar alloys and the formation of δ-ferrite in the dissimilar heat-affected zones (HAZ) and DWZ were analytically quantified. Moreover, the diffusion activity of carbides/interstitial carbon atoms was examined by Secondary ion mass spectroscopy (SIMS). In the FSW joints, the intermingled microstructures are recorded with high and stabilized hardness values as compared to the DWZ of the ATIG and LBW joints. In the transverse tensile test, all FF joints were failed at the 316 L(N) base metal (BM) region. Tensile and impact testing of all weld metal indicated that, the weld metal region of the LBW joint exhibited higher strength and lower toughness as compared to the ATIG and FSW joints. The presence of untransformed, recrystallized fine equiaxed austenite along and refined martensitic structure arranged in an alternate layers within the weld metal region of FSW joint caused the higher toughness property than the ATIG and LBW joints.

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Investigation on keyhole mode fiber laser welding of SS 316 in a self-protected atmosphere

Cited by 5 publications

References 31 publications

Probing the stress corrosion cracking resistance of laser beam welded AISI 316LN austenitic stainless steel

Probing the stress corrosion cracking resistance of laser beam welded AISI 316LN austenitic stainless steel

Numerical Study on the Influence of the Plasma Properties on the Keyhole Geometry in Laser Beam Welding

Decisive impact of Filler-free joining processes on the Microstructural evolution, tensile and impact properties of 9Cr-1Mo-V-Nb to 316 L(N) dissimilar joints

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