Microstructural characteristics and mechanical properties of carbon nanotube reinforced Inconel 625 parts fabricated by selective laser melting

Highlights: • Carbon nanotube reinforced Inconel 625 produced by selective laser melting shows improved strength with reduced elongation. • Electron backscattering diffraction patterns revealed the grain refinement for carbon nanotube reinforced Inconel 625. • The Inconel 625 composite recovered its elongation after heat treatment while maintaining its ultimate tensile strength. Selective laser melting (SLM) was used for additive manufacturing multi-wall carbon nanotube (MWCNT) reinforced Inconel 625 composites. The MWCNTs were coated on Inconel 625 powder through molecular-level mixing. Compared to the SLM fabricated Inconel 625 sample, the composite sample showed significant improvement in ultimate tensile and yield strength with less elongation. Heat-treatment on the composite sample recovered its elongation to the level of pure Inconel 625 while maintaining its ultimate tensile strength but reducing its yield strength. The microstructures of the composite sample had a slightly faster cooling rate than the pure metallic sample during SLM fabrication. The electron backscatter diffraction graphs revealed the grain refinement induced by MWCNTS in the alloy matrix. The Raman spectra and TEM micrographs revealed the presence of MWCNT in the metal matrix after SLM fabrication.