Fabrication of porous metallic materials by controlling the processing parameters in selective laser melting process

Abstract

Porous metallic materials are materials that have closed cell or open cell pores within their microstructure. These materials have high stiffness-to-weight ratios and serve as good heat exchanging materials due to the high surface area. Selective Laser Melting (SLM) method of additive manufacturing (AM) can manufacture these materials to save more time and provides more intricate designs compared to traditional manufacturing. The aim of this study was to manufacture porous materials by controlling the processing parameters (laser power, scanning speed, layer thickness, and hatch spacing) that affect the energy density applied on the metal powder during the melting. Lower energy density applied in the laser melting process leads to higher porosity. The experiments were designed using an L9 orthogonal array through Taguchi’s method to minimize the number of runs carried out. SLM Tool Steel 1.2709 specimens were manufactured with three levels of each processing parameters that contribute to a lower energy density compared to the standard energy density of 69.4 J/mm3. The relative density of each specimen was measured using Archimedes’ methods and converted to Signal-to-Noise (S/N) Ratios. The S/N ratios were used to analyze the ranking of parameters to the effect of relative density through MINITAB. The ranking of parameters was confirmed by conducting Analysis of Variance (ANOVA) analysis with the S/N ratios and comparing the percentage contribution of each parameter towards the relative density of the specimens. Hatch spacing was found to have the most effect on the relative density the most followed by laser power, layer thickness and scanning speed. Regression analysis was conducted to obtain a regression equation for relative density in terms of the four SLM processing parameters. Confirmation tests will be conducted by fabricating porous specimens with the regression equation with a targeted relative density and measuring the relative density of the fabricated specimen.