Effect of TiC on the microstructure of GTD-111 superalloy processed by laser powder bed fusion

Abstract

• TiC particles cause heterogeneous nucleation by altering the diffusion field in LPBF. • GBs liquation and GBs cracking is the most important LPBF problem in GTD-111. • The addition of TiC to GTD-111 causes the formation of equiaxed grains and zigzag of GB. • The favorable thermal conductivity of TiC prevents crystal formation in the GTD-111 matrix. • GTD-111 composite with TiC reduces the tendency of GB cracking by increasing C-GBLD. In this study, the microstructure of specimens made of GTD-111 superalloy was modified by laser powder bed fusion with TiC nanoparticles. The results showed that TiC particles acted as heterogeneous nucleation for solidification and caused grain refinement, equiaxed grain formation, grain boundary length reduction, increase of large angle grain boundaries, zigzagging of grain boundary, reduction of cracks and porosity and also reduces the segregation of elements sensitive to melting cracks. The combination of the above factors reduced the grain size by adding TiC by 40%.