The effect of boron and zirconium on the microcracking susceptibility of IN-738LC derivatives in laser powder bed fusion

The effect of boron (<0.01 to 0.03 wt%) and zirconium 0.07 on the microcracking susceptibility γ’-strengthened Ni-base superalloy IN-738LC during laser powder bed fusion (LPBF) was studied using custom designed grades. It found that both elements have a strong susceptibility, microcracks are located at high angle grain boundaries based EBSD measurements crack density increases with content elements. High in material corresponds large fraction intergranular decohesion facets exhibiting dendritic morphology fracture surface, typical for solidification cracking. Investigation surface chemistry by X-ray photoelectron spectroscopy (XPS) indicates considerable amounts B Zr present oxide state. Auger electron (AES) confirms segregated surface. Thin layers B- Zr-containing microcrack surfaces were indicated atom probe tomography (APT) as well. Hence, it is suggested cracking alloying system caused formation high-angle solidification.