Evaluation of solidification cracking of Ni-based alloy dissimilar welds based on Trans-Varestraint test

The hot cracking (solidification cracking) susceptibility in the weld metals of duplex stainless steels were quantitatively evaluated by Transverse-Varestraint test with gas tungsten arc welding (GTAW) and laser beam welding (LBW). Three kinds of duplex stainless steels (lean, standard and super duplex stainless steels) were used for evaluation. The solidification brittle temperature ranges (BTR) of duplex stainless steels were 58K, 60K and 76K for standard, lean and super duplex stainless steels, respectively, and were comparable to those of austenitic stainless steels with FA solidification mode. The BTRs in LBW were 10-15K lower than those in GTAW for any steels. In order to clarify the governing factors of solidification cracking in duplex stainless steels, the solidification segregation behaviours of alloying and impurity elements were numerically analysed during GTAW and LBW. Although the harmful elements to solidification cracking such as P, S and C were segregated in the residual liquid phase in any joints, the solidification segregation of P, S and C in LBW was inhibited compared with GTAW due to the rapid cooling rate in LBW. It followed that the decreased solidification cracking susceptibility of duplex stainless steels in LBW would be mainly attributed to the suppression of solidification segregation of P, S and C.

Download Full-text

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

Materials Science Forum ◽

10.4028/www.scientific.net/msf.782.3 ◽

2014 ◽

Vol 782 ◽

pp. 3-7

Author(s):

Kenji Shinozaki ◽

Motomichi Yamamoto ◽

Kohta Kadoi ◽

Peng Wen

Keyword(s):

High Speed ◽

Video Camera ◽

Solidification Cracking ◽

In Situ Observation ◽

High Speed Video Camera ◽

Varestraint Test ◽

Solidification Cracks ◽

Observation Method ◽

Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

Download Full-text

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

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2020.58.6.403 ◽

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.

Download Full-text

Studies on Susceptibility of Alloy 617 to Solidification Cracking

Materials Science Forum ◽

10.4028/www.scientific.net/msf.969.34 ◽

2019 ◽

Vol 969 ◽

pp. 34-40

Author(s):

R. Ravibharath ◽

K. Devakumaran ◽

V. Muthupandi

Keyword(s):

High Temperature ◽

Gas Turbines ◽

Hot Cracking ◽

Solidification Cracking ◽

High Temperature Strength ◽

Test Results ◽

Alloy 617 ◽

Creep Properties ◽

Varestraint Test ◽

Super Alloy

Ni based super alloy 617 is widely used in transition liners in both aircraft and land-based gas turbines, power plant applications because of its high temperature strength, oxidation resistance and creep properties. Ni based alloys are highly susceptible to hot cracking like solidification and liquation racking issues. In this present work, the susceptibility of alloy 617 to solidification cracking is studied based on the varestraint test. Results of this weldability test proved that in addition to the solidification cracking susceptibility alloy 617 is prone to liquation cracking also. Keywords: Varestraint test, Alloy 617, Solidification cracking, Liquidation cracking.

Download Full-text