Effect of ERNiFeCr-2 Filler Metal on Solidification Cracking Susceptibility of CM247LC Superalloy Welds

Solidification cracking during lithium-ion battery packaging was metallurgically investigated, specifically for Cu-steel dissimilar materials. To this end, single-mode fiber and green lasers were employed under heat input conditions ranging from 1.3 to 8.0 J/mm. For both laser welds, solidification cracking was concentrated in the steel region of the fusion zone, particularly in the locally Cu-depleted region, regardless of the welding condition. Modified self-restraint tests were performed for overlapping dissimilar material combinations to elucidate the mechanism of solidification cracking. Analysis of the solidification cracking surface revealed that approximately 15?30 mass% Cu existed on the surface. Cu was highly enriched with a droplet shape, formed during solidification within the miscibility gap. By calculating the non-equilibrium weld mushy zone range based on the diffusion-controlled Scheil’s model, the solidification cracking in the Cu-depleted region was estimated at 453 K. It was strongly affected by the severe segregation of Cu (95.7 mass%) in the residual liquid at the terminal stage of the solidification path. Therefore, from a welding metallurgical perspective, homogeneous Cu distribution and minimization of Cu segregation within the fusion zone are essential for suppressing or minimizing the solidification cracking susceptibility of Cu?steel dissimilar laser welding.

Section: Estimation Of Non-equilibrium Mushy Zone Rangementioning

confidence: 97%

Hot Cracking Characteristics During Single-Mode Fiber and Green Laser Welding Processes in Lithium-Ion Battery Pack Manufacturing

Park,

Kim,

Kang

et al. 2023

“…본 연구에서 주목하고 있는 블레이드 소재 는 일방향응고용 247LC 초내열합금으로, 해당 소재는 용접 고온균열(응고 및 액화균열)에 취약한 소재로 잘 알려져 있다 6,7) . 본 저자는 247LC 초내열합금 용접부 의 응고 및 액화균열 민감도 최소화를 위한 용접야금학 적 인자 규명에 대한 다양한 선행연구 결과를 보고한 바 있다 4,5,[7][8][9][10][11] . 가스텅스텐아크용접(Gas Tungsten Arc Welding, GTAW)을 이용한 Varestraint 시험으로부터,…”

Section: 서 론unclassified

Strategy of Suppressing the Solidification Cracking Susceptibility of 247LC Superalloy Weld Metals using Commercial Ni-Based Fillers

Chun¹

2023

The solidification cracking susceptibility of 247LC superalloy dissimilar welds with ERNiCrCoMo-1, ERNiCrMo3, and ERNiFeCr-2 commercial fillers was quantitatively evaluated using Varestraint testing for the sound weld geometries of gas turbine blades. We confirmed that the solidification brittle temperature range (BTR) of the 247LC/ ERNiCrMo-3 dissimilar weld was 217 K, which was measured using a thermo-vision camera during the Varestraint testing, and the BTR increased to 260, and 485 K with the ERNiCrCoMo-1 and ERNiFeCr-2 fillers, respectively, Based on theoretical calculations of the weld solidification path (i.e., using Scheil’s model; performed via the software Thermo-Calc) for each dissimilar weld, the variation in the BTR can be considered to be highly dependent on the solid-liquid coexistence temperature range of the dissimilar welds, and it is also correlated with the low-temperature formation of topologically closed packed phases during the terminal stage. Based on the experimental and theoretical results, the commercial Ni-based filler ERNiCrMo-3 is expected to be an effective welding material for 247LC dissimilar welding and the successful manufacturing of high-soundness blades.

“…대한용접․접합학회지 제41권 제4호, 2023년 8월 255 향응고 및 단결정 니켈계 초내열합금을 기반으로 한 각 종 고부가 소재부품의 제조기술 국산화 연구개발이 활 발하게 진행되고 있다. 해당 부품(예: 가스터빈 블레이 드, 베인 등)들은 신품 제조 [1][2][3][4] 및 유지보수 [5][6][7] 시 용 접 및 적층제조 공정의 적용이 필수적이며, 따라서 용 접 야금학적 현상의 이해를 바탕으로 한 용접 건전성 확보는 해당 부품의 성능, 내구성과 직결되는 주요 핵심 공정기술이다. 하지만 일방향응고 및 단결정 초내열합 금들은 용접 시 고온균열이 발생하는 난용접(Difficultto-weld) 소재들로 잘 알려져 있어, 용접 건전성 확보 에 상당한 어려움이 있다 1,6,[8][9][10] .…”

unclassified

“…해당 함금에 대한 Varestraint 균열 시험 결과로부터, 응고균열발생 온도범위(Solidification Brittle Temperature Range, BTR)는 400 K 1) , 액화 균열발생 온도범위(Liquation Cracking Temperature Range, LCTR)는 620 K 11) 으로 보고된 바 있으며, 이는 용접 승온 및 냉각 과정 상의 1,000 K이라는 넓 은 온도범위에 걸쳐 고온균열이 발생될 수 있음을 의미 한다. CM247LC 합금의 용접 응고균열 만감도를 저 감시키기 위해, 용접성이 우수한 상용 용가재 적용 2,3) , 응고모드 제어 1) 그리고 저입열 급속용융 레이저 공정 의 적용 12) 등이 검토된 바 있으며, 특히 최근에는 용융 부에서의 응고결정립계 형성 억제를 통한 무균열 용접 가능성을 제시한 연구결과도 보고되고 있다 13) . 한편 CMSX-4, CMSX-10 등의 대표적인 단결정 초내열합 금에서도 적층제조 시 응고균열이 발생하는 등, 상당한 난용접 소재로 알려져 있으나, CM247LC 합금과 같 이 균열 민감도의 정량평가 등 용접 야금학적 검토에 대해서는 그 선행 결과가 부족한 실정이다 9) .…”

unclassified

Solidification Crack Free Welding Strategy via Ultra High Precision Laser Scanning at a Single Grain of Directionally Solidified and Single Crystal Superalloys

Lee,

Kim,

Kang

et al. 2023

In this study, possibility of solidification crack-free welding of directionally solidified CM247LC and single crystal CMSX-4 superalloys was metallurgically investigated using single-mode fiber laser scanning. The key metallurgical factors of solidification cracking have been identified as the formation of highly misoriented solidification grain boundaries (low level of epitaxial growth behavior) at the fusion zone that affects the repulsive force between two adjacent dendrites and dendrite coalescence undercooling at the terminal stage of weld solidification. In particular, under extremely low heat input and ultra-high-speed laser beam scan conditions (welding speed: 1,000 mm/s, heat input: 2 J/mm, and energy density: 65 J/mm<sup>2</sup>), an effective fusion zone could be achieved within a single directionally solidified grain of CM247LC alloy owing to the characteristics of single-mode fiber laser. The fusion zone successfully showed a 99.9% of epitaxial growth achievement ratio (that is, low fraction of highly misoriented solidification grain boundaries at the fusion zone) without solidification cracking. Based on these results on CM247LC alloy, solidification crack-free welds could be successfully achieved using quadruple-pass and square-type weld geometries.