Cracking mitigation of additively manufactured Inconel 738LC through addition of micro-TiC particles

Abstract

The widespread application of Inconel 738LC in laser additive manufacturing is limited due to its poor formability, inferior weldability, and heightened crack susceptibility resulting from its high titanium + aluminum content. In this study, we propose adding micro-sized TiC particles into Inconel 738LC to improve its printability and cracking resistance. Inconel 738LC and Inconel 738LC-1 wt% TiC samples were fabricated by laser powder bed fusion with varying processing parameters. The microstructural characteristics, crack characterization, crack suppression mechanisms, and microhardness properties were comprehensively investigated. Results reveal that solidification cracking and liquation cracking predominate in Inconel 738LC samples. Severe micro-segregation at grain boundaries and continuous oxide-rich liquid films contribute to grain boundary embrittlement and promote cracking. The addition of TiC particles markedly reduces defects such as lack of fusion and cracks. Added TiC particles play a crucial role in refining microstructures and facilitating the precipitation of nano-sized MC carbide particles. A more equiaxed grain shape with tortuous grain boundaries is conducive to impeding crack propagation. Reduced local strain concentration and diminished micro-segregation also contribute to crack suppression. The principal mechanisms for microhardness enhancement in Inconel 738LC-TiC samples encompass densification behavior, grain boundary strengthening, and Orowan strengthening.