Crack mitigation in selective laser melting of CM247LC superalloy via post-heating laser tracks: Influence on microstructure and cracking behavior

Abstract

The selective laser melting (SLM) process for fabricating CM247LC nickel-based superalloy components is often limited by severe cracking. This study explores the use of a post-heating laser track as a method to mitigate cracks during SLM processing by providing localized pre-heating. The effects of post-heating energy input on density, microhardness, cracking characteristics, microstructure, and cracking mechanisms were systematically analyzed. Results show that without post-heating, there was a weak correlation between volumetric energy density (VED) and material density, with densities ranging from 8.18 to 8.60 g/cm³ and peaking at 107.1 J/mm³. Microhardness remained largely unaffected by VED, but a weak positive correlation was observed when post-heating was applied. Cracking characteristics, including crack length and frequency, were significantly influenced by the post-heating energy input, with 80 % energy input yielding the best results in reducing crack lengths. Furthermore, the post-heating process induced grain refinement, increasing grain equiaxity and altering the dominant cracking mechanism from intergranular to ductility dip cracking at lower energy inputs. Although cracks were not entirely eliminated, reducing crack lengths typically offers promising improvements for the fatigue performance of the material. This study highlights the potential of post-heating laser tracks as a practical solution for crack mitigation in SLM-fabricated CM247LC components.