Reducing cracking sensitivity of CM247LC processed via laser powder bed fusion through composition modification

Abstract

CM247LC, a Ni-based superalloy widely used in the aerospace industry due to its exceptional high-temperature performance, faces severe cracking issues in laser powder bed fusion (L-PBF) processing. This study investigates the effects of removing Hf and reducing Al content on the cracking and mechanical behaviors of LPBF-processed CM247LC. Microstructure characterization and thermodynamic calculation reveal that removing Hf narrows the solidification interval, reduces the fraction and size of inter-dendritic MC carbides, and thereby lowers its susceptibility to hot cracking. Decreasing Al content reduces the fraction and size of the γ'/γ eutectic phase and γ′ phase, alleviates local stress concentration, and enhances resistance to solid-state cracking. After chemical modification, the alloy exhibits a remarkable 96% reduction in crack density, a 75% reduction in crack length, and an 86% reduction in porosity, but displays comparable or even higher mechanical properties compared to LPBF-processed CM247LC. The effects of composition modification on the distribution of other elements, the precipitation of MC carbides and γ′ phase, the formation of annealed twins, the room and high temperature strength and ductility, are analyzed in detail. This study demonstrates that conventionally designed alloys can be adapted to the L-PBF process through compositional modification, achieving reduced defects and retained mechanical properties. The findings in this work are also instructive for alloy design tailored for the L-PBF process.

Keywords

• CM247LC
• Laser powder bed fusion
• Additive manufacturing
• Cracking sensitivity