Multi-Material Metal Powder Bed Binder Jetting Using PVA Binder

Abstract

This research presents a study of a novel multi-material deposition system developed for the deposition of powder and the creation of components using the Binder Jetting approach to print stainless steel and copper multi-material parts that can be used in thermal management applications. Experimental investigations into deposition nozzle diameter, head movement speed, and ultrasonic power levels of the novel multi-material deposition system reveal the effects on powder deposition heaps, establishing a correlation between ultrasonic power levels and powder heap characteristics. The derived regression equation is validated, affirming its accuracy. Polyvinyl Alcohol (PVA) is explored as a binder material, with emphasis on concentration, wettability, and thermal behaviour. Optimal structural strength and rapid powder bed infiltration are achieved with a 5% PVA concentration dissolved in deionized water. Furthermore, 38 sintering cycles have been conducted to study the dynamic interaction between 316L stainless steel and copper. Iterative adjustments in temperature and dwelling times ensure precision in parameter control, addressing challenges and maintaining structural integrity. The study extends to the evaluation of porosity as a process response, highlighting the critical importance of optimizing sintering conditions for different materials. An examination of the 316L and Cu bonding interface reveals good metallurgical bonding, supported by compositional analysis through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Tensile testing underscores high bond strength, with brittleness in 316L and Cu components attributed to insufficient sintering. The result of this research endeavour materialized in the successful development of a pioneering multi-material deposition system, consequently achieving a milestone in the fabrication of metal multi-material binder jetted components. Moreover, the thorough optimization of building process parameters encompassing speed, nozzle diameter, and ultrasonic power, coupled with judicious binder optimization and improved heating cycles, led to the fabrication of solid binder-jetted components made of two distinct materials characterized by disparate thermal properties. The study resulted in outcomes that show a good bonding interface between the two distinct materials. The multi-material components exhibited nearly 98% density, good interlayer connection, and improved tensile properties to copper itself, affirming the success of the proposed approach.