Minor Elements and Solidification Cracking During Laser Powder-Bed Fusion of a High γ CoNi-Base Superalloy

Evan B. Raeker, Kira M. Pusch, Stéphane A.J. Forsik, Ning Zhou, Austin D. Dicus, Qing Qiang Ren, Jonathan D. Poplawsky, Michael M. Kirka, Tresa M. Pollock

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The cracking behavior of a high γ volume fraction CoNi-base superalloy fabricated via laser powder bed fusion (LPBF) is studied in relation to the content of carbon and boron. Severe cracking occurred with the increase in boron content from 0.08 to 0.16 at. pct (0.015 to 0.029 wt pct), while compositions with 0.1 to 0.36 at. pct C (0.02 to 0.076 wt pct) and 0.08 at. pct B exhibited minimal cracking. Assessment of cracks in the high-boron composition shows a variation in crack density with printing parameters, and alignment of the cracks with the build direction. Scanning electron microscopy (SEM) of the crack surfaces shows evidence of a solidification cracking mode. Differential thermal analysis (DTA) reveals a decreased incipient melting temperature for the high-boron composition, and atom probe tomography (APT) is used to measure the enrichment at grain boundaries, revealing distinct boron segregation. Scheil-Gulliver solidification simulations for the different C and B levels are consistent with the incipient melting behavior observed with DTA. Evaluation of the solidification cracking susceptibility from the simulations allow for comparison of the CoNi alloy behavior to Ni-base superalloys studied for LPBF fabrication and displays how such metrics may aid in the design of new precipitation-strengthened superalloys for additive manufacturing (AM).

Original languageEnglish
Pages (from-to)1744-1757
Number of pages14
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume54
Issue number5
DOIs
StatePublished - May 2023

Funding

The research reported here made use of shared facilities of the National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara, DMR-172025. The UC Santa Barbara MRSEC is a member of the Materials Research Facilities Network (www.mrfn.org). A portion of this research was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC and performed in partiality at the Oak Ridge National Laboratory’s Manufacturing Demonstration Facility, an Office of Energy Efficiency and Renewable Energy user facility. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to acknowledge James Lamb for developing the python script used to analyze the DTA heating curves. The data that support the findings of this study are available from the corresponding author upon reasonable request. UCSB has a pending patent (T.M.P. as one of the inventors) on the CoNi alloys investigated: High Temperature Oxidation Resistant Co-based Gamma/Gamma Prime Alloys DMREF-Co, US patent application number US16/375,687, publication number US20200140978A1, international patent application number PCT/US2019/025882, international publication number WO2019195612A1. All other authors declare no competing interests. The research reported here made use of shared facilities of the National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara, DMR-172025. The UC Santa Barbara MRSEC is a member of the Materials Research Facilities Network ( www.mrfn.org ). A portion of this research was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC and performed in partiality at the Oak Ridge National Laboratory’s Manufacturing Demonstration Facility, an Office of Energy Efficiency and Renewable Energy user facility. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to acknowledge James Lamb for developing the python script used to analyze the DTA heating curves.

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