On the measurement of effective powder layer thickness in laser powder-bed fusion additive manufacturing of metals

In laser powder-bed fusion (LPBF), the actual thickness of powder particles that spread on solidified zones, so-called effective layer thickness (ELT), is higher than the nominal layer thickness. The source cause of this discrepancy is the fact that powder particles substantially shrink after selective melting, followed by solidification. ELT, as an unknown parameter, depends on process parameters and material properties. In this study, an effective method to measure ELT is proposed and applied to 17-4 PH stainless steel for a nominal build layer thickness of 20 µm. The measured ELT was larger than 100 µm, which is far beyond the values reported in the literature. Results obtained from the current study show the effect of applying the ELT rather than the nominal build layer thickness in numerical modeling studies as well as understanding the governing physics in the LPBF process.