• Journal of Welding and Joining
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• v.15 no.5
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.93-104
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• 1996

This study evaluated relative hot cracking susceptibility of commercial aluminum alloy welds, and then suggested possible mechanisms operated in the weld fusion zone and in the heat affected zone based on the observed cracking morphologies, fractography and microstructural features. The fusion zone solidification cracking was found to be mainly due to a microsegregation of Cu, Si, and Mg in grain boundaries, while liquation cracking in the HAZ was by the incipient melting of the segregated grain boundaries and the consitutional liquation of large aging precipitates and intermetallic compounds in the partially melted zone adjacent to the fusion line which experienced a rapid thermal excursion during welding.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.65-72
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• 2004

The tendency and degree of hot cracking of high strength 5083, 6N01 and 7N01 Al alloy welds by using DCSP-GTAW through modified Varestraint test and autogenous butt welding were investigated. In hot cracking test, 6N01 alloy showed the highest susceptibility to hot cracking in the weld metal and HAZ. Cracking susceptibilities generally increased with increase of solidification temperature range of the base metal and bead penetration-to-width ratio of the weld metal. The cracks in welds of the alloys vertically formed to solid-liquid interface and propagated along with columnar grain boundaries. The fracture facets of cracks showed the typical morphology of solidification crack observed as dendritic structures. Especially, in 6N01 alloy, liquation cracks which were due to elements of Si, Fe and Mg also observed in HAZ near fusion boundary. In butt welding of different Al alloys, the bead crack was mainly occurred in the welds of 6N01, 7N01 and other Al alloys together with 6N01 or 7N01. In the butt welds of 7N01, it was found that the component of Cu had an effect on the higher susceptibility to the hot cracking.

• Journal of Welding and Joining
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• v.13 no.3
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• pp.65-76
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• 1995

Weldability of DS100 and HY type high strength-toughness steel plates, tentatively produced as domestic production, was investigated. DS100 and DS130A had nearly same hardenability in HAZ in spite of its difference in Ceq. Based upon the y-groove test results, cold cracking susceptibility of DS130 was superior to that of DS100 because of its lower hydrogen level in weld metal. Solidification cracking tested by the Trans-Varestraint test was occured in all of the weld metals, and its susceptibility was high in the row of DS100, DS130A and DS130B. However, no liquation cracking and ductility-dip cracking tested by the Longi-Varestraint test with 6.0% augmented strain were detected in base metal and reheated weld metal. Toughness in the GMA welding joint was satisfied with the relative Mill Spec, even though welded joint of DS100 had relatively low impact energy especially at the weld metal.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.73-78
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• 2011

Weldability, especially HAZ cold cracking, weld metal solidification cracking, and HAZ liquation cracking susceptibilities, of ASTM A356 CA6NM martensitic stainless steel casting was investigated and compared with that of 9-12% Cr ferritic steel castings. Irrespective of the Cr and Ni content in the castings, the HAZ maximum hardness increased with an increase of carbon content. CA6NM steel, which has the lowest carbon content, had the lowest HAZ hardness and showed no cold cracking in y-slit cracking tests. CA6NM steel, meanwhile, showed the largest weld metal solidification cracking susceptibility in varestraint tests because of its higher amount of impurity elements, phosphorus, and sulfur. All castings investigated had good high temperature ductility in hot ductility tests and showed little difference in liquation cracking susceptibility.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.31-38
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• 2013

The transition of serrated grain boundary and its effect on liquation behavior in the simulated weld heat-affected zone (HAZ) have been investigated in a wrought Ni-based superalloy Alloy 263. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse ${\gamma}^{\prime}$ particles or $M_{23}C_6$ carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. The present study was initiated to determine the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a hot-cracking resistant microstructure. A crystallographic study indicated that the serration led to a change in grain boundary character as special boundary with a lower interfacial energy as those terminated by low-index {111} boundary planes. It was found that the serrated grain boundaries are highly resistant to boron enrichment, and suppress effectively grain coarsening in HAZ. Furthermore, the serrated grain boundaries showed a higher resistance to susceptibility of liquation cracking. These results was discussed in terms of a significant decrease in interfacial energy of grain boundary by the serration.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.52-55
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• 1998

• Journal of Welding and Joining
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• v.20 no.3
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• pp.74-83
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• 2002

In order to investigate the hot cracking phenomena of the Inconel 690 overlay welds, the hot cracking test(modified Varestraint test) was performed by varying augmented strain and welding speed in GTAW. A total of five kinds of specimens was used in the hot cracking test. The specimens used were two kinds of one layer specimens that were composed of just Inconel 690 deposited metal and three kinds of double layer specimens that were composed with as upper part of Inconel 690 weld metal and lower part of SA508 cl.3 or STS 309L. The main results are as fo11ows: In the welds composed of just Inconel 690, as the augmented strain was more increased and the welding speed was more decreased, the extent of cracking was more increased. And these cracks were mainly solidification cracks, and liquation cracks were also observed partially in HAZ. And hot cracking susceptibily of Inconel 690 welds by using filler metals containing Nb were higher than that of the welds with Nb free. The hot cracking susceptibility of Inconel 690 weld metal was increased with dilution of SA 508 cl.3 and STS 309L, and the influence of SA 508 cl.3 was higher than that of 575 309L. The results of calculation of $TSC\Delta$ and $TLC\Delta$ in Inconel 690 weld metal changed by dilution with base metal or neighboring welds were agreed well with the results of hot cracking test in this study. Therefore, it was expected that the hot cracking was considerably decreased or prevented by using proper welding conditions such as lower heat input, filler metals, base metal and neighboring welds.

• Journal of Welding and Joining
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• v.20 no.2
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• pp.82-89
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• 2002

In order to clarify hot cracking phenomena occurred in Inconel 690 welds and it's prevention, in this study, the cracking behavior and the influence of welding variables on cracking in Inconel 690 overlay welds on Mn-Ni-Cr-Mo steel(SA 508 cl.3) for pressure vessel were investigated by using mock-up test. The main results are as follows: The cracks in Inconel 690 overlay welds were mainly generated near the start and the end part of welding beads adjacent to STS 309L welded outside of Inconel 690 welds. Most of the cracks showed typical solidification crack, and also it was assumed that there was possibility of liquation cracking in HAZ. The existence of Nb constituents or concentration of Nb was recognized on the fracture facets of the solidification cracks in the welds by SMAW. Therefore Nb was considered to be the main factor of the solidification cracking. As the weld heat input was more increased and the weld bead length was longer, the extent of cracking was more increased. Moreover the extent of cracking was considerably decreased by changing of welding sequence to the start and the end part of welds. Hot cracking in welds by GTAW was considerably decreased as compared with that of SMAW. And cracks were well generated in the Inconel 690 overlay welds adjacent to 575 309L welds. This means that the hot cracking susceptibility of Inconel 690 welds was largely varied by chemical components and/or compositions of filter metals, base metals and neighboring welds.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.7-7
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• 2008