Formation and Control of Microcracks in K477 Superalloy Fabricated by Selective Laser Melting

FANG Lijia; SUN Bingbing; ZHAO Haisheng; ZHANG Qiang; HE Ruikai

doi:10.3969/j.issn.1674-6457.2026.02.016

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (2) : 169-182. DOI: 10.3969/j.issn.1674-6457.2026.02.016

Additive Manufacturing

Formation and Control of Microcracks in K477 Superalloy Fabricated by Selective Laser Melting

FANG Lijia^1,*, SUN Bingbing^1,2, ZHAO Haisheng^1,2, ZHANG Qiang^1,2, HE Ruikai³

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Abstract

The work aims to investigate the formation causes of micro-defects during the forming process of K477 nickel- based superalloy via selective laser melting, as well as the evolution rules of microstructure with respect to process parameters, thereby providing theoretical support and practical guidance for achieving high-quality forming processes. With K477 alloy formed under two typical SLM (Selective Laser Melting) process parameters of high power and low power as the research objects, the affecting factors of microcracks were analyzed by observing their microscopic morphology, as well as the distribution and content of various elements. Subsequently, K477 alloy specimens were formed by adjusting different laser scanning speeds (700, 800, 900, 1 000, 1 100, and 1 200 mm/s) and laser powers (150, 200, 250, 300, 350, and 400 W). Optical microscopy was employed to analyze internal defects, X-ray diffraction (XRD) was used to examine the phase composition, and scanning electron microscopy (SEM) was combined to investigate the evolution rules of the microstructure. Under two typical process parameters, a γ+γ° eutectic phase was observed at crack sites within the materials formed by selective laser melting. The distribution maps of aluminum (Al) at the cracks corresponded to those of carbon (C) and oxygen (O). Moreover, notable local enrichment of carbon and oxygen elements was observed near the cracks. By adjusting different laser powers and scanning speeds, it was found that as the laser scanning speed increased to 800 mm/s, the relative density reached 99.970%. When the laser power increased to 350 W, the relative density reached 99.977%. The presence of the γ+γ° eutectic phase within the selective laser melted K477 material is the primary cause of crack formation. During the solidification process, aluminum (Al) elements contribute to the formation of carbides, oxides, as well as nickel-chromium oxides, which acts as crack initiation sites near the grain boundaries. The variation in heat flow distribution caused by differences in laser scanning energy indicates that optimizing process parameters can suppress crack formation to a certain extent.

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selective laser melting / laser forming / superalloy / additive manufacturing / 3D printing

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FANG Lijia, SUN Bingbing, ZHAO Haisheng, ZHANG Qiang, HE Ruikai. Formation and Control of Microcracks in K477 Superalloy Fabricated by Selective Laser Melting[J]. Journal of Netshape Forming Engineering. 2026, 18(2): 169-182 https://doi.org/10.3969/j.issn.1674-6457.2026.02.016

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