Effect of scanning strategy on microstructure and mechanical properties of GH5188 alloy fabricated by laser powder bed fusion

This study systematically investigates the effects of long-line and short-line scanning strategies on the microstructure and mechanical properties of GH5188 superalloy fabricated by laser powder bed fusion (LPBF). Metallography and SEM results reveal that both strategies produce mixed microstructures composed of columnar and equiaxed grains. Due to the shallower melt pool and insufficient remelting, the short-line strategy retains finer grains at the melt-pool center, leading to further grain refinement (17.17 μm). In contrast, the long-line strategy provides a more stable heat-flow direction, resulting in stronger〈001〉texture development along the build direction and a slightly larger average grain size (20.86 μm). Mechanical testing shows that the two strategies lead to similar tensile strength and ductility at room temperature. At 980 ℃, the tensile strengths are comparable, while the elongation of the long-line specimens is 28.6% higher than that of the short-line specimens. Under the 927 ℃/90 MPa stress rupture condition, the long-line specimens exhibit a significantly longer rupture life (50.2 h±1.8 h) and higher ductility (10.1%±0.5%) than the short-line specimens (45.3 h±2.1 h; 7.6%±0.4%). Cross-sectional analysis shows that the short-line specimens contain more densely distributed cracks, along with pronounced carbide precipitation and coarsening at grain boundaries, indicating higher grain-boundary damage sensitivity. Fractographic analysis further confirms that cracks preferentially propagate along grain boundaries. These findings clarify the microstructural origins of high-temperature performance differences and provide guidance for optimizing LPBF scanning strategies for GH5188 alloy.