Role of elemental reduction in microstructure, microcrack, and mechanical properties of GH3230 by laser powder bed fusion

Two kinds of pre-alloyed GH3230 powders, each with different Si and Mn compositions, were employed to fabricate components through laser powder bed fusion (LPBF). Microstructural analysis reveals that microcrack formation in the GH3230 sample results from both microsegregation and thermal cycling-induced strain. Both samples with different contents of Si and Mn exhibit typical epitaxial growth of columnar dendrites with directional anisotropy, indicating minimal variation in microstructure under identical thermal cycling conditions. The occurrence of hot cracking is influenced by various factors, with chemical composition playing a crucial role. The presence of these cracks significantly impacts the mechanical properties of the component. The ultimate tensile strength and elongation of the GH3230-L sample, which has reduced Si and Mn content, show significant improvements compared to the GH3230 sample. The ultimate tensile strength increases from 735.0 MPa to 790.0 MPa, and elongation rises substantially from 11.3% to 35.2%. Thermodynamic simulations confirm that variations in Si and Mn content influence hot cracking sensitivity. Reducing Si and Mn levels narrows the solidification range, which helps to minimize the formation of hot cracks by enhancing liquid filling at grain boundaries.