Effect of powder reuse on powder characteristics and properties of Inconel 718 parts produced by selective laser melting

Abstract

Recycling metallic powders used in the selective laser melting (SLM) process is beneficial to reduce the manufacturing cost and promote resource sustainability. However, current research about the effect of powder reuse on the final SLM part is still limited. In this work, a systematic study was made to explore the recycled powder characteristics, microstructures and mechanical properties of the SLM Inconel 718 (In718) part. Results show that the powder reuse cycles can increase the particle size but not change its chemical composition. With the increase of reuse times, the apparent density increases and the flowability becomes better. The In718 parts fabricated by the recycled powder exhibit similar microstructure characteristic with dark austenite matrix and some white Laves phases. X-ray computed tomography (CT) was used to characterize the pores inside the parts. More tiny pores (deq≤50) and higher pore sphericity (ϕs≥0.6) are formed as the reuse times increase. More importantly, powder reuse between 1st-14th times has no negative effect on the mechanical properties of the SLM In718 parts. Room-temperature tensile test on both virgin and recycled powders shows a similar room-temperature tensile properties, such as 1025 MPa ultimate tensile strength, 750 MPa yield strength and 27%–30% elongation, achieving the application requirements of In718 alloy in the ASTM standard. This work provides a useful insight into the powder reuse of In718 alloy for SLM process.

Keywords

• Selective laser melting
• Powder reuse
• Inconel 718 alloy
• Pore defects