Figure 2 identifies key differences between SLM manufactured ring parts using Inconel 718 and Aluminium powders. Aluminium still exhibits unmelted or partially melted particles resulting from too low laser power or too fast laser scanning, while Inconel reveals a uniform melting front confirming optimised laser settings.
In addition to providing a powerful 3D visualisation of morphology differences, the Contour optical profiler quantifies and ranks process quality through advanced roughness S parameters from ISO norm 25178. This drives iterative optimisation of process conditions. The following specific parameters best discriminate between Al and Inconel based process:
- Ssk (Skewness) quantifies degree of symmetry above/below the mean plane characterizing the number of extreme peaks or valley structures. Zero value stands for perfect symmetry while a negative value indicates a higher number of cavities/pores and a positive value emphasizes a predominance of unmelted particles
- Sdr expresses how corrugated/porous the surface is
- Ssc is the Mean Summit Curvature for the various peak structures revealing presence of aggregated or partially melted particles
- Sm represents the mean spacing between asperities or spikes
The surface from the Inconel ring is indeed smoother (Figure 2) due to better optimised process conditions delivering improved fusion of the particle bed. Specifically, it exhibits (a) lower corrugation evidenced from Sdr differences, (b) a flatter surface with longer radius of curvature proved by 60% higher Ssc, and (c) contains longer spacing between asperities/spikes proved by the 57% larger Sm value.
Bruker’s Vision64 Map software enables immediate databasing of all those key roughness parameters making it possible to build custom experimental models. Modelling then provides a faster time to accurate results without blind trial & error process changes.
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