A comparing study of defect generation in IN738LC superalloy fabricated by laser powder bed fusion: Continuous-wave mode versus pulsed-wave mode

Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes. Microstructure, surface quality and mechanical properties were compared to evaluate the printing quality between these 2 laser beam modes. The results show that the application of pulsed wave could effectively eliminate cracking in the as-fabricated sample, despite 0.046% porosity generated. Further microstructure analysis revealed that the refinement of grains by the pulsed-wave laser beam was the main contributor in eliminating the cracks. And this refinement was ascribed to the higher cooling rate under the discontinuous radiation of laser beam proofed by the numerical simulation. And the pore formation was related to Rayleigh instability and residual bubbles in the sample under the pulsed-wave mode, while pores were less detrimental to the mechanical properties than cracks. Therefore, the part under the pulsed-wave mode exhibited superior mechanical performance compared to that under the continuous-wave mode.