Abstract
The susceptibility of nickel-based superalloys to processing-induced crack formation during laser powder-bed additive manufacturing is studied. Twelve different alloys—some of existing (heritage) type but also other newly-designed ones—are considered. A strong inter-dependence of alloy composition and processability is demonstrated. Stereological procedures are developed to enable the two dominant defect types found—solidification cracks and solid-state ductility dip cracks—to be distinguished and quantified. Differential scanning calorimetry, creep stress relaxation tests at 1000 °C and measurements of tensile ductility at 800 °C are used to interpret the effects of alloy composition. A model for solid-state cracking is proposed, based on an incapacity to relax the thermal stress arising from constrained differential thermal contraction; its development is supported by experimental measurements using a constrained bar cooling test. A modified solidification cracking criterion is proposed based upon solidification range but including also a contribution from the stress relaxation effect. This work provides fundamental insights into the role of composition on the additive manufacturability of these materials.
| Original language | English |
|---|---|
| Pages (from-to) | 962–983 |
| Number of pages | 22 |
| Journal | Metallurgical and Materials Transactions A |
| Volume | 53 |
| Early online date | 8 Jan 2022 |
| DOIs | |
| Publication status | Published - Mar 2022 |
Bibliographical note
Acknowledgments:The financial support of this work by Alloyed Ltd. and the Natural Sciences and Engineering Research Council of Canada (NSERC) in the Chemical, Biomedical and Materials Science Engineering division award number 532410. The authors acknowledge funding from Innovate UK, under project number 104047, specifically the Materials and Manufacturing Division. The authors thank sincerely the referees and editors for their fair-minded critique of our manuscript, which has restored our faith in the reviewing process and the scientific method more broadly.