Mechanical properties, carbon absorbance and melt pool analysis of laser melting of metal-polymer composite for metal additive manufacturing

Abstract

Metal Additive manufacturing using Powder Sheets (MAPS) is a recently proposed solution to various challenges in powder based additive manufacturing. Understanding of the interactions between carbon absorption, plume generation and keyholing is critical for successful utilisation of MAPS. MAPS feedstock is a metal powder and polymer composite sheet that can have a yield strength ranging from 0.3 ± 0.1 MPa to 1.7 ± 0.5 MPa depending on the polymer concentration, with higher concentrations experiencing more gradual and ligament type failure. This study presents that 27.8 ± 3.8 % of the carbon present in the powder sheet is absorbed by the bulk material during MAPS, irrespective of the polymer concentration in the composite. Most of the carbon is lost due to polymer vaporisation and the formation of gases, therefore generating significant plume and causes effects such as powder sheet detachment from the scan area and laser obstruction. At high laser scan speeds, carbon in the form of a black residue remains on the print surface. This interaction with the polymer leads to enhanced keyholing across a variety of laser scanning speeds and produces melt pools with larger depth-to-width ratios than typical powder. Across the energy densities studied there is an average 41 ± 18 % increase in depth-to-width variation between MAPS and loose powder printing.