scholarly journals Evaluation and Control of Liquation Cracking Susceptibility for CM247LC Superalloy Weld Heat-Affected Zone via Visualization-Based Varestraint Test

2021 ◽  
Vol 59 (7) ◽  
pp. 445-458
Author(s):  
Ye-Seon Jeong ◽  
Kyeong-Min Kim ◽  
Hyungsoo Lee ◽  
Seong-Moon Seo ◽  
Eun-Joon Chun
Keyword(s):  
Laser Beam ◽  
Fossil Fuels ◽  
Cast Alloy ◽  
Laser Beam Welding ◽  
Aging Treatment ◽  
Liquation Cracking ◽  
Cracking Behavior ◽  
Temperature Range ◽  
Varestraint Test ◽  
Weld Heat

The metallurgical aspects of weld cracking in Ni-based superalloys remain relatively unexplored in existing research. The present study performed comprehensive metallurgical and manufactural investigations into the weldability of an Ni-based superalloy, CM247LC, from the viewpoint of the liquation cracking behavior and its susceptibility. Metallurgical solutions to suppress the liquation-cracking susceptibility were derived via the visualization-based Varestraint test, and the possibility of liquation crack-free welding was explored by employing pre-weld heat treatments and laser beam welding. The alloy that was subjected to aging treatment exhibited the lowest liquation-cracking susceptibility (liquation cracking temperature range: 66 K), while the as-cast alloy specimen exhibited the highest liquation-cracking susceptibility (liquation cracking temperature range: 620 K). The metallurgical mechanisms of the liquation cracking susceptibility of as-cast CM247LC weld were elucidated via microstructural analyses and thermodynamic calculations. The suppressed liquation cracking susceptibility of the aged CM247LC can be attributed to the MC-type carbide fraction and homogenized matrix phase, as compared with those of as-cast CM247LC. The aged CM247LC specimen was subjected to gas tungsten arc welding to validate its minimal liquation-cracking susceptibility. The results confirmed the suppression of liquation cracking, due to the low susceptibility of the specimen. However, crackfree welds could not be obtained. Finally, metallurgically sound welds without liquation cracks were successfully obtained via laser beam welding. The outcomes of the present study will facilitate the generation of electric power from fossil fuels via a clean and efficient gas turbine-based power generation cycle.

scholarly journals Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 985 ◽  
Author(s):  
Pedro Alvarez ◽  
Lexuri Vázquez ◽  
Noelia Ruiz ◽  
Pedro Rodríguez ◽  
Ana Magaña ◽  
...  
Keyword(s):  
Grain Size ◽  
Laser Beam ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Welding Parameters ◽  
Minor Effect ◽  
Alloy 718 ◽  
Material Source ◽  
Cross Sectional ◽  
Varestraint Test

Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 is usually welded in a solution annealed state. However, even with this thermal treatment, cracks can be induced during standard industrial manufacturing conditions, leading to costly and time-consuming reworking. In this work, the cracking susceptibility of wrought and investment casting alloy 718 is studied by the Varestraint test. The test is performed while applying different welding conditions, i.e., continuous tungsten inert gas (TIG), low frequency pulsed TIG, continuous laser beam welding (LBW) and pulsed LBW. Welding parameters are selected for each welding technology in order to meet the welding quality criteria requested for targeted aeronautical applications, that is, full penetration, minimum cross-sectional welding width and reduced overhang and underfill. Results show that the hot cracking susceptibility of LBW samples determined by the Varestraint test is enhanced due to extended center line hot cracking, resulting in a fish-bone like cracking pattern. On the contrary, the minor effect of material source (wrought or casting), grain size and pulsation is observed. In fact, casting samples with a 30 times coarser grain size have shown better performance than wrought material.

scholarly journals Effect of Cladding Conditions on Solidification Cracking Behavior during Dissimilar Cladding of Inconel Alloy FM 52 and 308L Stainless Steel to Carbon Steel: Evaluation of Solidification Brittle Temperature Range by Transverse−Varestraint Test

2020 ◽  
Vol 58 (6) ◽  
pp. 403-412
Author(s):  
Yookyung Kim ◽  
Byungrok Moon ◽  
Namhyun Kang ◽  
Eun-Joon Chun
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Arc Welding ◽  
Differential Method ◽  
Solidification Cracking ◽  
Cracking Behavior ◽  
Factors Affecting ◽  
Inconel Alloy ◽  
Temperature Range ◽  
Varestraint Test

In this study, solidification cracking behavior and susceptibility in dissimilar cladding of Inconel alloy FM 52, 308L stainless steel to carbon steel, was investigated by submerged arc welding and transverse−Varestraint testing with gas tungsten arc welding. The effect of cladding conditions on cracking behavior and susceptibility was extensively evaluated, and metallurgical factors affecting susceptibility were clarified. Depending on the cladding sequence (cladding combination A: Inconel 52→308L, cladding combination B: 308L→Inconel 52), opposite types of solidification cracking behavior were observed. Specifically, solidification cracking was observed only for cladding combination A. Using transverse−Varestraint tests, the solidification brittle temperature range (BTR) was determined to be 298 K for cladding combination A and 200 K for cladding combination B. The reason for solidification cracking in cladding combination A could be its higher solidification susceptibility (i.e., a larger BTR (298 K)) compared with cladding combination B (BTR: 200 K). To elucidate differences in solidification cracking susceptibility, a numerical simulation of non−equilibrium solidification segregation for impurity elements (P, S) was performed, based on velocity dependent solidification theories and the finite differential method. Different segregation behaviors were calculated upon the cladding combinations. The severe segregation of P and S during solidification was found to be one of the important metallurgical factors for the large BTR of cladding combination A, compared with cladding combination B.

scholarly journals Investigation of Metallurgical and Mechanical Properties of Laser Beam Welded and Post-weld Heat Treated DP1400 Steel

2021 ◽  
Author(s):  
Raghawendra P. S. Sisodia ◽  
Marcell Gáspár
Keyword(s):  
Mechanical Properties ◽  
Laser Beam ◽  
Diode Laser ◽  
Lath Martensite ◽  
Laser Beam Welding ◽  
Sheet Thickness ◽  
Ductile Failure ◽  
Tensile Tests ◽  
Coarse Grained ◽  
Weld Heat

AbstractIn this paper, the effect of autogenous diode laser beam welding (LBW) and the influence of post weld heat treatment (PWHT) on microstructural changes and mechanical properties of dual phase DP1400 high strength steel (HSS) butt welded joint are studied and presented. LBW and PWHT were performed on 1 mm sheet thickness using 3 and 5 kW diode laser systems, respectively. The technology ensures high quality welded joints in HSS and facilitate the welding and PWHT by same process and equipment. Microstructure evaluation was performed using optical and scanning electron microscopy. Related to the mechanical properties, tensile tests, fractography of fractured tensile specimens and three-point bending tests were carried out. The microstructural examination presented the constituents of martensite and ferrite in the heat affected zone (HAZ) and fusion zone (FZ) consists of predominantly lath martensite with ferrite and some bainite. Tempered martensite was observed after PWHT in HAZ and FZ. The hardening peaks observed in coarse-grained and fine-grained subzones were significantly reduced by the novelty technology, i.e. PWHT and thereby cold cracking sensitivity. The fractography of the fractured tensile specimens showed characteristic features of ductile failure.

scholarly journals Hot-cracks reduction during Laser Beam Welding in vacuum of conventionally cast Alloy-247 LC

Procedia CIRP ◽  
2020 ◽  
Vol 94 ◽  
pp. 632-637
Author(s):  
Aleksej Senger ◽  
Torsten Jokisch ◽  
Simon Olschok ◽  
Uwe Reisgen ◽  
Thomas Fischer
Keyword(s):  
Laser Beam ◽  
Cast Alloy ◽  
Laser Beam Welding ◽  
Conventionally Cast
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