Composition modification and experimental verification of Hastelloy X superalloy with superior mechanical properties fabricated by laser powder bed fusion

Hastelloy X superalloy has been extensively utilised in the aerospace industry owing to its exceptional high-temperature stability. Nevertheless, this material exhibits significant cracking susceptibility during laser powder bed fusion (LPBF) process. This investigation presents a d-electron alloy design approach to mitigate cracking sensitivity and enhance the printability of Hastelloy X superalloy. Comprehensive microstructural analysis and mechanical evaluations revealed that increasing solid solution strengthening elements (Cr, Co, Mo, and W) while reducing trace elements (C, Ti, and Si) effectively narrowed the solidification temperature range by 45.9% and diminished liquid film formation, thereby alleviating cracking propensity. Post-modification characterization demonstrated a remarkable reduction in defect density, with total volumetric defects (including pores and cracks) decreasing from 0.96% to 0.07% in LPBF-processed specimens. Detailed microstructural analysis identified two distinct cracking mechanisms: solidification cracking along interdendritic regions and liquation cracking associated with secondary phases. The modified alloy showed a remarkable reduction in liquation cracking due to suppressed carbide precipitation and reduced elemental segregation. The modified alloy exhibited superior high-temperature performance at 900°C, demonstrating 20% enhancement in ultimate tensile strength (from 210.2 MPa to 252.2 MPa) and 370% improvement in elongation (from 6.0% to 28.2%) along the building direction compared to conventional counterparts. This study systematically elucidates the interplay between chemical composition, solidification dynamics, phase evolution, and mechanical performance through characterization techniques and thermodynamic modelling. The successful implementation of this alloy design strategy provides a methodological framework for developing crack-resistant nickel-based superalloys with enhanced high-temperature capabilities for additive manufacturing (AM) applications. • A novel alloy design approach suitable for Hastelloy X superalloy was proposed. • The influence of chemical composition on cracking sensitivity was discussed. • A modified alloy with improved tensile strength and ductility was developed.