Influence of Hot Isostatic Pressing on Different Crack Modes of Laser Powder Bed Fusion-Processed CM247LC: Alternative Process Parameters Considering Post-processing

Abstract

Nickel-based superalloys, including CM247LC, fabricated using laser powder bed fusion (LPBF) are prone to cracking. These induced cracks significantly reduce a manufacturability of the LPBF fabricated components; therefore, selecting appropriate process parameters is critical. Standard sample-scale LPBF parameters often lead to cracking in large-scale applications due to thermal energy accumulation and low thermal conductivity. Thus, it is important to explore industrial-scale parameters and post-processing methods, such as hot isostatic pressing (HIP), to mitigate cracking. However, the effectiveness of HIP can be reduced in samples fabricated under high volumetric energy density (VED) conditions. This study examines the impact of HIP on CM247LC samples fabricated under various VED conditions (43.65-159.72 J/mm3). Two distinct crack modes were identified, namely, solidification and liquation cracks at high and low VED conditions, respectively. A comparison of the pre- and post-HIP crack densities revealed that the crack healing effect of HIP under low and high VED conditions was approximately 90 and 47%, respectively. The mechanisms behind the healing of closed cracks, mostly liquation cracks, were analyzed. This study provides novel insight for selecting LPBF process parameters in the low VED range to mitigate cracks, with a quantitative analysis of HIP treatment for healing two types of cracks. These findings are crucial for practical applications in engineering fields such as the energy, aerospace, and automotive industries.