Selective Laser Melting of Crack-Free Ti-48Al-2Cr-2Nb Alloy: Improved Manufacturability by Powder Surface Modification Using Graphene Oxide

Abstract

Intermetallic γ-TiAl based alloys have been developed for high-temperature lightweight applications in aerospace and automotive industries. However, their fabrication via selective laser melting (SLM) remains a great challenge due to the severe cracking issue and unsatisfied mechanical properties. In this study, we present a novel manufacturing strategy to significantly improve the printability of a Ti-48Al-2Cr-2Nb (Ti-4822, at.%) alloy for SLM by powder surface modification. Specially, graphene oxide (GO) sheets were decorated onto the metallic powder surface via the electrostatic adsorption process. Results indicated that crack-free samples could be fabricated by adding 0.1–0.5 wt.% GO during SLM experiments. The microstructure as affected by GO addition was characterized by backscatter electron imaging and electron backscatter diffraction, showing that the dual-phase (α2 + γ) cellular structure was refined at both grain and sub-grain scales. Further characterization by a three-dimensional focused ion beam-scanning electron microscopy tomography demonstrated the increased volume fraction of γ phase and the reduced porosity with GO addition. Finally, the surface strength of as-fabricated Ti-4822 was evaluated by microhardness test, demonstrating a maximal enhancement of 21.9% when modified using 0.3 wt.% GO. We envision that the proposed manufacturing strategy has provided new perspectives for the design and production of high-performance γ-TiAl based alloys via SLM.