Selective Laser Melted Inconel 718
Selective Laser Melting (SLM) of Inconel 718, a high-strength nickel-based superalloy, is highly sensitive to scanning strategies, which significantly influence the material’s mechanical properties. Research combining Digital Image Correlation (DIC) with micro-tensile testing and microstructural analysis reveals that the scanning strategy affects cooling rates, grain structure, and surface characteristics, leading to distinct mechanical behaviors in bulk versus thin-wall samples. For instance, bulk samples exhibit statistically different strength and ductility compared to thin-wall samples, even when printed with identical parameters, due to variations in microstructure and surface roughness driven by the scanning approach.
The aligned scanning strategy in thin-wall samples results in slower cooling rates and abundant nucleation sites from surrounding powder, producing smaller grain sizes and lower texture compared to bulk samples. This leads to greater variability in mechanical properties, with thin-wall samples showing locally high surface roughness that triggers multiple crack formations and premature failure under load. In contrast, a rotated scan strategy disrupts multi-layer grain formation in thin-wall samples, further altering the microstructure. These findings highlight that complex SLM parts with thin-wall features require careful design, as local geometry and scanning strategy directly impact microstructure and mechanical performance, and thin-wall properties cannot be inferred solely from thickness.
Read more on this project:
a. T. C. Varney, T. Oldham, M. I. Noor, and P. F. Rottmann, “Quantifying the Microstructure and Mechanical Property Differences between Bulk and Thin-wall Additively Manufactured Inconel 718″, Materialia, vol. 31, 2023.