Nickel-based superalloys(Haynes 230)fabricated by laser powder bed fusion suffer from high cracking suscepti-bility,leading to a decrease in mechanical performance.In this study,the cracking mechanism of Haynes 230 wa...Nickel-based superalloys(Haynes 230)fabricated by laser powder bed fusion suffer from high cracking suscepti-bility,leading to a decrease in mechanical performance.In this study,the cracking mechanism of Haynes 230 was investigated based on microstructural and thermodynamic calculations.It was found that C and carbide-forming elements(such as Mo and Cr)were segregated at the grain boundaries,which increased the solidification range and impeded liquid film backfalling by forming nano-carbides.Additionally,the coalescence of high-angle grain boundaries(>15°)requires a higher undercoolingΔT_(b)than that of low-angle grain boundaries(2-15°),which increases the susceptibility to hot cracking.Through gradually reducing laser energy input,the grain size is sig-nificantly decreased from 27.86μm(47.40 J/mm^(3))to 14.66μm(31.81 J/mm^(3)).Moreover,the calculated cooling rate|dT∕dt|and temperature gradient|dT∕ds|gradually increase with decreasing energy input,which reduces the duration of dendrite merging and shortens the length of the liquid film.Compared with cracked samples,the optimized sample showed superior mechanical properties,including high yield strength(678 MPa),ultimate tensile strength(943 MPa),and elongation to failure(19.2%),which increased by 16.1%,9.7%,and 77.7%,respectively.展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFB3707405)National Natural Science Foun-dation of China(Grant Nos.U22A20113,52371135,52201156)+2 种基金Hei-longjiang Provincial Natural Science Foundation of China(Grant No.TD2020E001)Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001)Heilongjiang Touyan Team Program.
文摘Nickel-based superalloys(Haynes 230)fabricated by laser powder bed fusion suffer from high cracking suscepti-bility,leading to a decrease in mechanical performance.In this study,the cracking mechanism of Haynes 230 was investigated based on microstructural and thermodynamic calculations.It was found that C and carbide-forming elements(such as Mo and Cr)were segregated at the grain boundaries,which increased the solidification range and impeded liquid film backfalling by forming nano-carbides.Additionally,the coalescence of high-angle grain boundaries(>15°)requires a higher undercoolingΔT_(b)than that of low-angle grain boundaries(2-15°),which increases the susceptibility to hot cracking.Through gradually reducing laser energy input,the grain size is sig-nificantly decreased from 27.86μm(47.40 J/mm^(3))to 14.66μm(31.81 J/mm^(3)).Moreover,the calculated cooling rate|dT∕dt|and temperature gradient|dT∕ds|gradually increase with decreasing energy input,which reduces the duration of dendrite merging and shortens the length of the liquid film.Compared with cracked samples,the optimized sample showed superior mechanical properties,including high yield strength(678 MPa),ultimate tensile strength(943 MPa),and elongation to failure(19.2%),which increased by 16.1%,9.7%,and 77.7%,respectively.
