Origin of hot cracking formation and suppression method in laser additive manufactured nickel-based superalloys

Although laser additive manufacturing is a promising technique for fabricating nickel-based single crystal superalloy components, reducing hot cracking during the deposition is still a challenge. In this study, the cracking susceptibility and microstructures with different substrates are investigated. Results show that samples exhibit much lower cracking susceptibility when using the directional solidified substrates than the cast polycrystalline substrates. Hot cracking is attributed to a stable liquid film dependent on the misorientation angle. Besides, liquation cracking first occurs in the substrate and could propagate by extension into solidification cracks along the high angle grain boundaries. Based on these findings, a crack-free nickel-based superalloy with a polycrystalline substrate is successfully prepared using a continuous scanning strategy.