Additive manufacturing of porous metals using laser melting of Ti6AI4V powder with a foaming agent

Recent years have seen researchers paying attention to the fabrication of porous structures by using additive manufacturing techniques suitable for the production of small batches. This paper focuses on the fabrication process and the compressive characteristics of a porous metal manufactured using the direct energy deposition (DED) process, which is a 3D printing technology for metals. Materials with structures containing internal pores were manufactured by spraying a mixture consisting of Ti6Al4V powder and a foaming agent (Na2CO3) onto a Ti6Al4V substrate, and subsequently fused with the substrate using a high-power laser beam. The ensuing molten pool undergoes rapid solidification, resulting in the formation of a metal layer. Before the molten metal solidifies, the carbon dioxide gas generated from Na2CO3 created pores inside the deposited layer. In this study, pored structures fabricated under various conditions were analyzed and compared from the viewpoint of compressive behavior. The results showed that the densities of the layered porous structures could be controlled by varying process parameters such as the laser power, scanning speed, powder feed rate, and mix ratio of the foaming agent. The most dominant parameters to obtain a pored structure were the amount of foaming agent and powder feed rate. The compression tests revealed that the porous materials manufactured using DED collapsed due to fracturing of the internal porous structures. After these structures fractured, the materials experienced densification, followed by crumbling. In addition, decreasing the laser power and scanning speed caused the compressive strength to decrease due to the high number of internal pores. Furthermore, before finally fracturing, the compressive strain decreased for specimens with increased porosity. The compression tests proved that the porous structure was able to effectively absorb compression loads.