Cracking inhibition of nano-TiC reinforced René 104 superalloy fabricated by selective laser melting

Highlights: • Nano-TiC reinforced René 104 superalloy with reduced defects and improved mechanical properties has been prepared by SLM. • Nano-TiC provides heterogeneous nucleation, which promotes the grain refinement and columnar-to-equiaxed grain transition. • The cracking inhibition is due to the refined grain, reduced HAZ area and equiaxed microstructure. • The improved tensile performance is attributed to the grain refinement and the reduction of cracking density. -- Abstract: The introduction of ceramic nanoparticles enables to inhibit the cracking of additively manufactured "hard-to-weld" nickel-based superalloy. Nevertheless, the mechanisms of cracking elimination have not been formed a consensus understanding. Additionally, the nanoparticles are difficult to be uniformly dispersed due to their high specific surface energy. In this study, TiC-René 104 nanocomposite powder was produced using micron-sized TiC particles by ball milling, and nano-TiC reinforced René 104 superalloy was fabricated by selective laser melting (SLM). The grain refinement and columnar-to-equiaxed grain transition of René 104 superalloy are effectively promoted as a result of the heterogeneous nucleation provided by TiC nanoparticles. The cracking density of as-printed TiC-René 104 is reduced by 83.3%, and the ultimate tensile strength and elongation are improved by 31.3% and 113.9%, respectively. The cracking inhibition is ascribed to the significant grain refinement, the diminishment of HAZ area and the formation of fine equiaxed microstructure. The research supplies a prospective approach to inhibit cracking and strengthen mechanical properties in the additively manufactured nickel-based superalloys with poor weldability.