The liquation cracking behavior of IN738LC superalloy during low power Nd:YAG pulsed laser welding

The Evolution of Cast Microstructures on the HAZ Liquation Cracking of Mar-M004 Weld

“…The induced microcracks were strongly related to inherent metallurgical factors of the Mar-M004 superalloy. As reported in previous works [20,21,24,25], constitutional liquation of MC carbides, M 3 B 2 borides, M 2 SC sulfocarbides, γ particles, and γ-γ eutectic accounts for the HAZ liquation cracking of IN 738 superalloy weld. The cracks were prone to propagate along the interfaces between the MC carbide and the matrix (Figure 5b), owing to substantial amount of MC carbides in the cast Mar-M004 superalloy.…”

“…Liquidation cracking in the HAZ is one of the most noticeable problems in welding or repair-welding of Ni-based superalloys such as IN 738 [7][8][9], Rene 80 [10][11][12][13], IN 939 [14,15], RR 1000 [16], IN 713C [17], and K465 [18]. Grain boundary liquation results from incipient melting of MC carbides, Cr-Mo borides, γ-γ eutectic and Ni-Zr intermetallics along the solidified boundaries [18][19][20][21][22][23][24]. The use of filler metals with (a) slower aging response, (b) smaller lattice mismatch between the precipitates and the matrix, (c) lowered (Ti + Al) concentrations and (d) softer weld metal have been reported to reduce the HAZ cracking susceptibility of IN 738LC welds [25].…”

“…The use of filler metals with (a) slower aging response, (b) smaller lattice mismatch between the precipitates and the matrix, (c) lowered (Ti + Al) concentrations and (d) softer weld metal have been reported to reduce the HAZ cracking susceptibility of IN 738LC welds [25]. Moreover, preweld heat treatments [10,14,15,[22][23][24] have been conducted to modify the microstructures of precipitate-strengthened Ni-based superalloys to decrease the sensitivity of liquidation cracking in the HAZ.…”

Liquation Cracking in the Heat-Affected Zone of IN738 Superalloy Weld

“…The terminal solidification products also consist of Ni 7 Zr 2 and M 3 B 2 formed in front of γ-γ' eutectic in IN738 superalloy [14]. Furthermore, these boride particles decrease the solidus temperature at which non-equilibrium intergranular liquation is induced in the HAZ during the heating cycle of welding, thereby enhancing the cracking susceptibility of the weld [38]. In prior studies, the borides and intermetallics at the interdendritic boundaries are more likely to melt during repair-welding of Mar-M004 superalloy [39,40].…”

Research on the Grain Boundary Liquation Mechanism in Heat Affected Zones of Laser Forming Repaired K465 Nickel-Based Superalloy

“…The main reason for cracking phenomenon is the generation of constitutional liquation and tensile stresses in the heat affected zone (HAZ) during LFR. When the stresses exceed the ability of the material's intrinsic resistance to cracking, cracks appear at grain boundaries in HAZ [9] and then spread into the repaired area along the grain boundaries. It is well known that the formation of liquation cracks depends in the presence of a continuous or Metals 2016, 6, 64; doi:10.3390/met6030064…”