Laser power influence on track's geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition

Additive manufacturing of metal matrix composite (MMC) is a challenging field to explore. Besides components' geometric constitution, requirements related to final microstructures must be met. Depending on the application, such as tribology, machining, or magnetism related, there is a need to preserve a specific phase, which is generally responsible for the engineering function of the fabricated component. This work analyzes the laser power (P) parameter influence on track's geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition (DED). Objectives are observing the interaction between Fe-alpha and Sn-based alloy as a function of P and, then, define a processing window that allows the MMC microstructure. Experimental methodology relied on single-tracks bead-on-plate deposits with P variations. To assess track's geometry and microstructure changes, postprocessing analyses were performed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Results show that P influences positively on tracks' height, width, and cross section area. Greater laser power resulted in higher geometric aspects. Microstructure evolution was observed as P was enhanced from 150 to 700 W. In lower P ranges, Fe particles are not strongly affected by the heat source, resulting in an MMC microstructure mainly composed by Fe-alpha dispersed on a Sn-rich alloying matrix. When more thermal energy is provided due to higher laser power levels, Fe and Sn diffuse to a greater extent, resulting in an increased quantity of Fe-Sn phases and a more homogeneous microstructure. EDS mapping suggests that formed phases are Fe solid solutions containing Sn. Then, it is concluded that MMC microstructures are possible to be achieved around a P window of 150 W.