Effect of parameters for dul-contours on the surface forming of nickel-based superalloys fabricated by LPBF

Although, laser powder bed fusion (LPBF) is widely used in the integrated manufacturing of nickel-based superalloy parts with complex structures in aerospace industry, it’s a relatively rough surface limits its application. In this paper, the surface forming quality was optimized by dual-contours scanning strategy. Meanwhile, the influences of the dual-contours parameters on the surface forming quality, microstructure and microhardness were investigated. The results show that the upper surface roughness S_a gradually decreases with the increase of the heat input of the dual-contours parameters. The roughness S_a reaches the optimal value of 3.1 μm when the power is 220 W and the scanning speed is 0.1 m/s. However, under high heat input, keyhole-induced hole defects will be formed on the near surface. Thus, surface roughness optimization requires comprehensive consideration of the keyhole-induced hole defects. In addition, there is no obvious correlation between the heat input of dual-contours parameters and the roughness of the lower surface. The lower surface roughness S_a of sample prepared under different contour parameters ranges from 13.5 μm to 16.5 μm. The unidirectional scanning strategy of the contour parameter results in the formation of coarse columnar grains, and the microhardness of the upper contour layer increases significantly with the increase of heat input.