scholarly journals Varestraint Testing of Selective Laser Additive Manufactured Alloy 718—Influence of Grain Orientation

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1113 ◽  
Author(s):  
Tahira Raza ◽  
Joel Andersson ◽  
Lars-Erik Svensson
Keyword(s):  
Weld Metal ◽  
Heat Affected Zone ◽  
Grain Orientation ◽  
Hot Cracking ◽  
Alloy 718 ◽  
High Angle ◽  
Electron Backscattered Diffraction ◽  
Varestraint Testing ◽  
Significant Difference ◽  
Haz Cracking

The effect of grain orientation on hot cracking susceptibility of selective laser additive manufactured Alloy 718 was investigated by Varestraint testing. Electron backscattered diffraction showed that cracks in heat affected zone (HAZ) of the welded samples occurred in high angle grain boundaries. The extent of HAZ cracking was smaller in samples tested parallel to the elongated grain orientation and larger in samples transverse to the elongated grain orientation. However, for solidification cracking in the weld metal, no significant difference with respect to grain orientation in the base metal was found.

scholarly journals Weldability Evaluation of Alloy 718 Investment Castings with Different Si Contents and Thermal Stories and Hot Cracking Mechanism in Their Laser Beam Welds

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 402
Author(s):  
Pedro Álvarez ◽  
Alberto Cobos ◽  
Lexuri Vázquez ◽  
Noelia Ruiz ◽  
Pedro Pablo Rodríguez ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Laser Beam ◽  
Hot Cracking ◽  
Laves Phase ◽  
Hot Ductility ◽  
Alloy 718 ◽  
Weldability Tests ◽  
Cracking Mechanism ◽  
Haz Cracking ◽  
Si Content

In this work, weldability and hot cracking susceptibility of five alloy 718 investment castings in laser beam welding (LBW) were investigated. Influence of chemical composition, with varying Si contents from 0.05 to 0.17 wt %, solidification rate, and pre-weld heat treatment were studied by carrying out three different weldability tests, i.e., hot ductility, Varestraint, and bead-on-plate tests, after hot isostatic pressing (HIP) and solution annealing treatment. Onset of hot ductility drop was directly related to the presence of residual Laves phase, whereas the hot ductility recovery behaviour was connected to the Si content and γ grain size. LBW Varestraint tests gave rise to enhanced fusion zone (FZ) cracking with much more reduced heat-affected zone (HAZ) cracking that was mostly independent of Si content and residual Laves phase. Microstructural characterisation of bead-on-plate welding samples showed that HAZ cracking susceptibility was closely related to welding morphology. Multiple HAZ cracks were detected in nail or mushroom welding shapes, typical in keyhole mode LBW, irrespective of the chemical composition and thermal story of castings. In all LBW welds, Laves phase with a composition similar to the eutectic of the pseudo-binary equilibrium diagram of alloy 718 was formed in the FZ. The composition of this regenerated Laves phase matched with the continuous Laves phase film observed along HAZ cracks. This was strong evidence of backfilling mechanism, which is described as wetting and infiltration of terminal liquid along γ grain boundaries of parent material. The current results suggest that this cracking mechanism was activated in three-point intersections resulting from perpendicular crossing of columnar grain boundaries with fusion line and was enhanced by nail or mushroom weld shapes and narrow and columnar γ grain characteristics of castings. Neither Varestraint nor hot ductility weldability tests can reproduce this particular cracking mechanism.

scholarly journals Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 881 ◽  
Author(s):  
Raza ◽  
Hurtig ◽  
Asala ◽  
Andersson ◽  
Svensson ◽  
...  
Keyword(s):  
Heat Affected Zone ◽  
Hot Isostatic Pressing ◽  
Heat Treatments ◽  
Alloy 718 ◽  
Gas Tungsten Arc ◽  
Material Condition ◽  
Heat Treated ◽  
Maximum Crack ◽  
Material Conditions ◽  
Haz Cracking

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

Weldability of superalloys alloy 718 and ATI® 718Plus™ – A study performed by Varestraint testing

2017 ◽  
Vol 59 (9) ◽  
pp. 769-773 ◽  
Author(s):  
Jonny Jacobsson ◽  
Joel Andersson ◽  
Anssi Brederholm ◽  
Hannu Hänninen
Keyword(s):  
Alloy 718 ◽  
Varestraint Testing

Hot Cracking Susceptibility of Nickel Base Alloy 718

1997 ◽  
Vol 30 (3) ◽  
pp. 14
Author(s):  
V. Shankar ◽  
G. Srinivasan ◽  
B. G. Muralidharan ◽  
T. P. S. Gill ◽  
V. K. Sethi
Keyword(s):  
Base Alloy ◽  
Hot Cracking ◽  
Alloy 718 ◽  
Nickel Base Alloy ◽  
Nickel Base

scholarly journals Mechanism of Hot Cracking in Multi-pass Weld Metal of Fe-36%Ni Invar Alloy. Welding of Fe-36%Ni Invar Alloy. (I).

2001 ◽  
Vol 19 (4) ◽  
pp. 664-672 ◽  
Author(s):  
Hiroyuki HIRATA ◽  
Kazuhiro OGAWA ◽  
Susumu HONGOU ◽  
Hiroshi IWAHASHI ◽  
Taketo YAMAKAWA ◽  
...  
Keyword(s):  
Weld Metal ◽  
Hot Cracking ◽  
Invar Alloy

Complex Monitoring Programme for WWER Reactor Pressure Vessels Lifetime Assessment in the Czech Republic

2008 ◽  
Author(s):  
Milan Brumovsky ◽  
Milos Kytka ◽  
Petr Novosad ◽  
Jiri Brynda
Keyword(s):  
Czech Republic ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Neutron Fluence ◽  
Pressure Vessels ◽  
Surveillance Program ◽  
The Czech Republic ◽  
Complex Monitoring ◽  
Metal Weld ◽  
Reactor Pressure

Lifetime of reactor pressure vessels practically depends on a level of degradation of RPV material properties during operation. The most important degradating mechanism of RPV materials is usually radiation damage, characterized by values on neutron fluence on one side and radiation embrittlement of RPV materials on the second side. WWER reactor pressure vessels in the Czech Republic are a subject of a very thorough and complex monitoring program, that includes: • Standard material surveillance program containing of WWER-440 RPV materials — base metal, weld metal, heat affected zone, but irradiated with high lead factor (13 to 18), • Supplementary surveillance program of WWER-440 RPV materials, including additionally austenitic cladding materials, IAEA reference material JRQ irradiated with low lead factor (2 to 3) with parts subjected to annealing and re-irradiation after annealing, • Modified surveillance program of WWER-1000 RPV materials — base metal, weld metal, heat affected zone, cladding materials, IAEA reference JRQ material irradiated in low lead factor (2 to 3) near RPV inner beltline region, • Integrated surveillance specimen program for WWER-1000 reactor including materials from NPP Temelin (Czech Republic), Belene (Bulgaria), Kalinin (Russia) and Ukranian NPPs, • Continous exvessel monitoring of neutron fluence on outer RPV surface for both WWER-440 and WWER-1000 plants, • Neutron fluence determination on inner RPV surface (austenitic cladding) using special technique for removal of specimens from cladding for Nb activity measurements, • Ex-vessel temperature measurements during RPV operation. All these programs serve for precision of operation conditions and determination of degradation of RPV materials for RPV integrity and lifetime assessment.

Effect of Post Weld Heat Treatment on Fusion and Heat Affected Zone Microstructure and Mechanical Properties of Inconel X-750 Welds

2011 ◽  
Vol 214 ◽  
pp. 108-112 ◽  
Author(s):  
Prachya Peasura ◽  
Bovornchok Poopat
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Aging Temperature ◽  
Post Weld Heat Treatment ◽  
High Aging Temperature ◽  
Zone Microstructure

The Inconel X-750 indicates good hot corrosion resistance, high stability and strength at high temperatures and for this reason the alloy is used in manufacturing of gas turbine hot components. The objective of this research was study the effect of post weld heat treatment (PWHT) on fusion zone and heat affected zone microstructure and mechanical properties of Inconel X-750 weld. After welding, samples were solutionized at 1500 0C. Various aging temperature and times were studied. The results show that aging temperature and time during PWHT can greatly affect microstructure and hardness in fusion zone and heat affected zone. As high aging temperature was used, the grain size also increased and M23C6 at the grain boundary decreased. This can result in decreased of hardness. Moreover excessive aging temperature can result in increasing MC carbide intensity in parent phase (austenite). It can also be observed that M23C6 at the grain boundary decreased due to high aging temperature. This resulted in decreasing of hardness of weld metal and heat affected zone. Experimental results showed that the aging temperature 705 0C aging time of 24 hours provided smaller grain size, suitable size and intensity of MC carbide resulting in higher hardness both in weld metal and HAZ.

scholarly journals Evaluation of Liquation Cracking Behavior and Susceptibility in Heat-Affected Zone of CM247LC Superalloy Welds for Turbine Blade Application

2020 ◽  
Vol 58 (12) ◽  
pp. 875-886
Author(s):  
Ye-Seon Jeong ◽  
Kyeong-Min Kim ◽  
Uijong Lee ◽  
Hyungsoo Lee ◽  
Seong-Moon Seo ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Heat Affected Zone ◽  
Solidus Temperature ◽  
Hot Cracking ◽  
Liquation Cracking ◽  
Cracking Behavior ◽  
Gas Tungsten Arc ◽  
Constitutional Liquation ◽  
Gas Tungsten ◽  
Eutectic Colony

In this study, the weldability of the as-cast CM247LC superalloy for turbine blade applications was metallurgically evaluated in terms of its hot cracking behavior and susceptibility. For this purpose, a real blade was manufactured using a directional solidification casting process, and gas tungsten arc welding was performed at the tip and cavity of the upper blade. Hot cracking was confirmed in the heat-affected zone (HAZ) of gas tungsten arc welds, and the cracks were characterized as liquation cracks, since a cobble or dropletshaped crack surface consistent with a liquid film was clearly confirmed. Microstructural analysis of the cracking surface and thermodynamic calculations helped elucidate the metallurgical mechanisms of the liquation cracking. In other words, the cracking was attributed to liquation of the γ-γ’ eutectic colony and the constitutional liquation of the MC-type carbides: these phases existed in the as-cast microstructure. In particular, it was calculated that liquation of the γ-γ’ eutectic colony during welding occurs at least at 1488 K and that constitutional liquation of MC-type carbides begins at 1411 K, while the equilibrium solidus temperature of the CM247LC alloy is 1530 K. Finally, the liquation cracking susceptibility was quantitatively evaluated through a spot-Varestraint test, and it was confirmed for the first time that the higher susceptibility of as-cast samples can be suppressed by employing a pre-weld heat treatment such as solution treatment.

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