Microstructural Characterization and Corrosion Behavior of Activated Flux Gas Tungsten Arc-Welded and Multipass Gas Tungsten Arc-Welded Stainless Steel Weld Joints in Nitric Acid

CORROSION ◽  
10.5006/0515 ◽  
2012 ◽  
Vol 68 (8) ◽  
pp. 762-773 ◽  
Author(s):  
A. Ravi Shankar ◽  
S. Niyanth ◽  
M. Vasudevan ◽  
U. Kamachi Mudali
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Delta Ferrite ◽  
Thick Sample ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Gtaw Process ◽  
Gas Tungsten

AISI Type 304L (UNS S30403) austenitic stainless steels are widely used in spent nuclear fuel reprocessing plants, and welding is an indispensable tool used for joining these materials. In the present study, manual gas tungsten arc-welded (M-GTAW) and activated gas tungsten arc-welded (A-GTAW) weldments of Type 304L stainless steel were prepared to examine the microstructural and corrosion behavior of the weldments. A total of 6 passes were required to complete the 6 mm thick sample welding, and 16 passes were required for 12 mm thick sample welding using the M-GTAW process, compared to single-pass A-GTAW welding. Characterization of weld joints was done by radiography, optical microscopy, microhardness tester, a feritscope, and scanning electron microscopy (SEM). The optical microstructure of the fusion zone of weld joints showed delta ferrite in various morphologies. The presence of delta ferrite stringers were observed in the weld joints, extending from the weld metal to the base metal. The corrosion rate results showed that the M-GTAW sample showed only a marginal increase in the corrosion resistance when compared to those welded by the single-pass A-GTAW process. SEM examination revealed the morphology of attack in the base metal was predominantly intergranular while in the weld metal it was interdendritic. The SEM micrograph also showed preferential attack of the delta ferrite stringers.

Role of welding processes on microstructure and mechanical properties of nuclear grade stainless steel joints

2019 ◽  
Vol 233 (11) ◽  
pp. 2335-2351 ◽  
Author(s):  
R Rajasekaran ◽  
AK Lakshminarayanan ◽  
M Vasudevan ◽  
P Vasantharaja
Keyword(s):  
Stainless Steel ◽  
Base Metal ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Nuclear Grade ◽  
Lower Percentage ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Welding Processes

Nuclear grade 316LN austenitic stainless steel weld joints were fabricated using conventional gas tungsten arc welding (GTAW), activated flux gas tungsten arc welding (AGTAW), laser beam welding (LBW) and friction stir welding (FSW) processes. Assessment of weld beads was done by mechanical and metallurgical characterizations. Bead geometry and weld zones were studied by taking macrographs along the transverse side of the weld joints. Metallurgical features of different weld joints were carried out using optical microscopy and scanning electron microscopy. Microhardness distribution across four weld joints was recorded and hardness variations were compared. All weld zone, heat affected zone (HAZ) of GTAW and LBW, thermo-mechanically affected zone (TMAZ) of FSW processes, exhibited higher hardness values than the base metal. Reduced hardness was recorded at HAZ of AGTAW process. This was the result of a considerable grain growth. LBW joint showed the highest hardness value at the center of the fusion zone due to fine equiaxed dendrite morphology. Tensile and impact properties of different welding processes were evaluated and comparisons were made at room temperature. All weld samples displayed high yield strength (YS) and ultimate tensile strength (UTS) with a lower percentage of elongation compared to that of the base metal. FSW joint showed improved YS, UTS and impact toughness compared to other weld joints. This is attributed to the formation of strain-free fine equiaxed grains at stir zone around 5 µm in size with subgrains of 2 µm in size by severe dynamic recrystallization mechanism. Among the fusion welding techniques, AGTAW process exhibited improved toughness, besides almost equal toughness of the base metal due to low δ-Ferrite with high austenite content. Fractography studies of the base metal and different weld samples were carried out by SEM analysis and features were compared.

Effect of Filler Alloy on Microstructure, Mechanical and Corrosion Behaviour of Dissimilar Weldment between Aisi 201 Stainless Steel and Low Carbon Steel Sheets Produced by a Gas Tungsten Arc Welding

2012 ◽  
Vol 581-582 ◽  
pp. 808-816 ◽  
Author(s):  
Chuaiphan Wichan ◽  
Srijaroenpramong Loeshpahn
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Weld Metal ◽  
Base Metal ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Delta Ferrite ◽  
Steel Sheets ◽  
Gas Tungsten Arc ◽  
Weld Metals

The joining of austenitic stainless steel (AISI 201) to low carbon steel sheets (CS) was attempted by gas tungsten arc welding (GTAW) with four types of consumables. The studied consumables were ER308L, ER309L, ER316L stainless steel wires, and AWS A5.18 carbon steel wire. The welding parameters – i.e. the current of 90 A and the welding speed of 62 mm.min-1 – were fixed in all welding operations. The microstructure of weld metal produced by stainless steel consumables consisted of delta ferrite in austenite matrix. The delta ferrite in the form of continuous dendrite was observed in weld metals produced by 308L and 309L fillers. The dendrite of delta ferrite was relatively discontinuous in weld metal produced by 316L filler. The microstructure of weld metal produced by carbon steel filler consisted of equiaxed ferrite and pearlite, similar to that of carbon steel. The corrosion behavior of weld metal was investigated by potentiodynamic method. Specimens were tested in 0.35-wt% NaCl solution saturated by laboratory air at 27°C. It was found that the corrosion potential of weld metal produced by carbon steel filler was considerably lower than those of AISI 201 base metal and weld metals welded using stainless steel consumables. Weld metals produced by stainless steel fillers –308L,309L and316L– exhibited the similar corrosion potentials as that of 201 base metal. The pitting potentials of weld metals produced by 309L, 316L fillers were higher than those of 201 base metal and weld metal produced by 308L filler respectively. It was discussed that the increase of Cr content in weld metals by using 309L filler contained with 24.791 wt% of Cr, or the addition of Cr and Mo in weld metals by using 316L filler contained with 21.347 wt% of Cr and 2 wt% of Mo, promoted the pitting corrosion resistance of weld metal to be comparable with that of Fe-17Cr-3Ni (201) base metal. An emission spectroscopy was applied to quantify the amount of elements in weld metals. By considering the contents of Cr and Mo, the pitting resistance equivalent number (PREN) of each weld metal was calculated. The discussion of the corrosion resistance of weld metals related to PREN and microstructure was made in the paper.

scholarly journals Correlation between Tensile Deformation Behavior and Microstructural Morphology of Nuclear Grade Austenitic Stainless Steel Weld Joints using Infrared Thermography Technique

2020 ◽  
Vol 92 (1) ◽  
pp. 7-15
Author(s):  
A.K. Lakshminarayanan ◽  
R. Rajasekaran ◽  
M. Menaka
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Infrared Thermography ◽  
Base Metal ◽  
Arc Welding ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Tensile Deformation Behavior

Tensile deformation behavior of nuclear grade Austenitic Stainless Steel (SS) and its weld joints fabricated by Gas Tungsten Arc Welding (GTAW) and Activated flux Gas Tungsten Arc Welding (AGTAW) processes were studied and correlated with relevant microstructural morphologies using Infrared Thermography (IRT) technique. The microstructure of base metal showed a complete austenite phase. GTAW Fusion Zone (FZ) exhibited both primary ferrite and primary austenite mode of solidification. Meantime, AGTAW FZ exhibited only primary austenite mode of solidification A strain rate of 4.4x10-4 s-1 was used during the tensile test of the base metal and weld samples. The failure locations of the base metal, GTAW and AGTAW samples were noticed at the center of the gauge portion, the base metal side away from Fusion Line (FL) and Heat Affected Zone (HAZ) respectively. Temperature variations of the base metal and weld zones were recorded in the form of thermograms using the IR camera at the different stages of the tensile deformation. During deformation study, peak temperatures of 39.2 oC, 38.8 oC and 34 oC were observed at the base metal, GTAW and AGTAW samples respectively. The lesser peak temperature of the AGTAW sample compared to the base metal and GTAW samples indicated that the AGTAW sample undergone lesser deformation. Moreover, tensile deformation behaviors of the base metal and weld samples were correlated with their microstructural morphologies using corresponding temperature curves.

Evaluation of Mechanical and Corrosion Properties of Base Metal and HAZ Having ASS 304L Forgings Containing Ferrite

2020 ◽  
Author(s):  
Ritesh Patel ◽  
Hardik Shah ◽  
Jimmy Dutt
Keyword(s):  
Base Metal ◽  
Hardness Test ◽  
Mechanical Tests ◽  
Delta Ferrite ◽  
Corrosion Properties ◽  
Gas Tungsten Arc ◽  
Significant Difference ◽  
Gtaw Process ◽  
Microstructure Examination ◽  
Mechanical And Corrosion Properties

Abstract Austenitic Stainless Steel type 304L is being widely used for fabrication due to excellent corrosion resistance and good weldability. Ferrite (3–10%) is needed in weld metal to prevent hot cracking during welding, however, base metal should preferably not contain any ferrite. It is observed that thick forged SS304L components may have small percentage of ferrite depending on the chemical composition, forging parameters including intermediate soaking cycle and final solution annealing heat treatment cycle. Little study or information is available on effect of ferrite in base metal on weld/Heat Affected Zone (HAZ) properties. Present study is aimed to evaluate mechanical and corrosion properties of weldment produced with base metal containing 2–4% of ferrite. Forged tubes with two different levels of delta ferrite, with < 0.5% & 2–4%, were welded to Plates with < 0.5% delta ferrite using Mechanized Gas Tungsten Arc Welding (GTAW) process with Inner Bore Welding Technique. Tensile test, Impact test and Hardness test were performed on base metal & HAZ in as-welded condition for both the cases. Microstructure examination in HAZ and Intergranular Corrosion (IGC) test were also performed for both the cases. Results of mechanical tests, microstructure examination and IGC test have been compared between base metal/HAZ of < 0.5% and 2–4% Ferrite base metal. No significant difference has been observed in test result of tubes with 2–4% delta ferrite as compared to tubes with < 0.5% delta ferrite.

Characterization of Duplex Stainless Steel/Cold Reduced Low Carbon Steel Dissimilar Weld Joints by GTAW

2015 ◽  
Vol 766-767 ◽  
pp. 780-788
Author(s):  
D. Devakumar ◽  
D.B. Jabaraj ◽  
V.K. Bupesh Raja ◽  
P. Periyasamy
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Carbon Steel ◽  
Duplex Stainless Steel ◽  
Base Metal ◽  
Arc Welding ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Weld Joints ◽  
Gas Tungsten Arc

The purpose of this study is to evaluate the mechanical and metallurgical properties of dissimilar metal weld joints between duplex stainless steel/Cold Reduced low carbon Steel (CRS) by Gas Tungsten Arc Welding (GTAW) process. The dissimilar 2 mm thickness plates of duplex stainless steel and cold reduced low carbon steel, conforming to AISI 2205 and IS 513_2008 CR2_D were butt welded by means of gas tungsten arc welding using argon as shielding gas. The butt welding joint arrangement was used for this experiment using E 309L electrode as filler metal. The joints were investigated for mechanical properties and microstructure. Tensile, Hardness and bend tests were carried out to evaluate the mechanical properties. Optical microscopy was used to explore the microstructure. The micro structural examination of the weld region revealed dendritic delta ferrite. Micro examination of DSS base metal revealed elongated grains of austenite (white) with ferrite (Brown). Micro examination of CRS base metal discloses deformed grains of ferrite present in the matrix. Fracture analysis was conducted for the failure part with Scanning Electron Microscope (SEM) and found ductile fracture occurred at CR steel side.

The Effect of Sodium Chloride Concentration on Corrosion Resistance of Austenitic Stainless Steel 316L and SMA Weldment

2017 ◽  
Vol 263 ◽  
pp. 120-124
Author(s):  
Andi Rustandi ◽  
Suganta Setiawan ◽  
Ihsan Fathurrahman
Keyword(s):  
Stainless Steel ◽  
Sodium Chloride ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Stainless Steel 316L ◽  
Impedance Magnitude

Austenitic stainless steel 316L has been widely used in marine environment which containing sodium chloride solution (NaCl). In order to provide matching properties with parent metal, filler metal SMA 316L is commonly produced with slightly over alloyed composition. This work investigated the corrosion behavior of base metal 316L and SMA 316L weld metal by using Electrochemical Impedance Spectroscopy (EIS) to evaluate the mechanism of corrosion behavior based on impedance magnitude measurement at room temperature (27°C ). Various concentrations of sodium chloride solution i.e 1%,2%,3.5%,4% ,and 5% NaCl were prepared. Optical Metallography was also conducted to compare microstructure of base and weld metal. By using Nyquist graphs and its related equivalent circuit parameters showed that impedance magnitude of weld metal was higher which compared to base metal at any NaCl concentration. Metallography examination revealed that weld metal 316L had dendritic austenitic with delta ferrite and 316L base metal had austenite with typical twin boundaries structure. Higher chromium and nickel content in weld metal 316L was the key variable that control passive film characteristic rather than its microstructure. The lowest impedance magnitude of both 316L and all-weld metal 316L at various concentration was at 3.5% NaCl. Dissolved oxygen at 3.5% NaCl reach maximum solubility which causes severe pitting corrosion.

scholarly journals Study of Microstructure 304L Austenitic Stainless Steel Weld Deposited by GTAW for Root Pass and SMAW for Filler Passes

2018 ◽  
Vol 7 (2) ◽  
pp. 21-25
Author(s):  
Harsimranjit Singh Randhawa
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Arc Welding ◽  
Rear Side ◽  
Gas Tungsten Arc ◽  
Metal Arc Welding ◽  
Gtaw Process

In the present experimentation, a 10mm thick austenitic stainless steel plate type 304L is welded using single V-joint configuration and approaching the joint from one side. Back purging has been employed to protect the rear side of the root pass weld metal against oxidation. The root pass has been deposited by gas tungsten arc welding (GTAW) process. The filler passes are deposited by shielding metal arc welding (SMAW) process at 90A and 120A welding currents giving heat inputs of the order of 0.679 and 0.933 kJ/mm respectively while the speed of weld deposition was kept practically constant. The results of experimentation show that the micro-hardness of weld metal and heat affected zone (HAZ) of weldments produced at lower heat input is higher whereas impact toughness value of weld metal and HAZ is lower than that of joints produced at higher heat input. The microstructure of weld metal and heat affected zone developed at lower weld heat input has been observed finer in comparison to that resulted at higher heat input. This has primarily happened due to a higher rate of cooling at low heat input.

Effect of current pulsing on super 304HCu weld joints

2019 ◽  
Vol 16 (6) ◽  
pp. 814-822
Author(s):  
Vinoth Kumar M. ◽  
Balasubramanian V.
Keyword(s):  
Tensile Properties ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Constant Current ◽  
Delta Ferrite ◽  
Content Type ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Super Austenitic Stainless Steel

Purpose Super 304HCu super austenitic stainless steel tubes containing 2.3 to 3 (Wt.%) of copper (Cu) is used in superheaters and reheater tubings of nuclear power plants. In general, austenitic stainless steels welded by conventional constant current gas tungsten arc welding (CC-GTAW) produce coarse columnar grains, alloy segregation and may result in inferior mechanical properties. Pulsed current gas tungsten arc welding (PC-GTAW) can control the solidification structure by altering the prevailing thermal gradients in the weld pool. Design/methodology/approach Super 304HCu tubes of Ø 57.1 mm and the wall thickness of 3.5 mm were autogenously welded using CC and PC-GTAW processes. Joints are characterized using optical microscopy, electron microscopy, energy dispersive spectroscopy and electron backscatter diffraction (EBSD) techniques. Hot tensile properties of the weld joints were evaluated and correlated with their microstructural features. Findings Current pulsing in GTAW has resulted in minimal eutectic film segregation, lower volume % of delta ferrite and appreciable improvement in tensile properties than CC-GTAW joints. Originality/value The EBSD boundary map and inverse pole orientation map of Super 304HCu weld joints evidence the grain refinement and much frequent high angle grain boundaries achieved using weld current pulsing.

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