Microstructure evolution and mechanical properties of high-chromium superalloy manufacturing by extreme high-speed laser metal deposition at different aging temperatures

Extreme High-Speed Laser Metal Deposition (EHLMD) is an efficient additive manufacturing technology that can quickly form difficult-to-machine materials. However, the rapid melting and solidification of EHLMD has the characteristic of forming a metastable microstructure. This study examines the effect of different aging temperatures on the microstructure and properties of EHLMD K648 superalloy. It is found that the formation of long needle-like alpha-Cr phase and gamma' phase at lower aging temperatures (750 degrees C and 800 degrees C) is more beneficial for improving the strength of EHLMD K648 superalloy. The tensile strength was highest at 750 degrees C (1236 MPa) but its elongation was low (9.4 %). As the aging temperature increased (850-900 degrees C), the alpha-Cr phase transformed into rods and small particles, resulting in a decrease in tensile strength and an increase in elongation. At 900 degrees C, the tensile strength was 918 MPa and the elongation was 21.0 %. With further increase in aging temperature (>900 degrees C), coarse carbide and alpha-Cr phase precipitated in EHLMD K648 superalloy, causing its tensile strength and elongation to decrease. When the aging temperature reached 1000 degrees C, the tensile strength and elongation decreased to 790 MPa and 13.3 %, respectively.