The influence of different ultrasonic impact treatment modes on microstructure and mechanical properties of 18Ni-300 steel fabricated by wire arc additive manufacturing

Abstract

This study investigates the introduction of ultrasonic impact treatment (UIT) during the wire arc additive manufacturing process to refine the microstructure and enhance the properties of 18Ni-300 maraging steel components. It was found that interlayer ultrasonic impact treatment (I-UIT) and synchronous ultrasonic impact treatment (S-UIT) applied to the deposited metal can refine the grains, alter grain growth orientation, and reduce anisotropy. At the top of the formed component, compared to directly deposited specimens, significant grain refinement and the appearance of a 20μm nanocrystalline zone were observed in I-UIT-WAAM samples, while S-UIT-WAAM samples similarly exhibited the effects of ultrasonic impact, with a deeper nanocrystalline zone of 230μm. In the middle of the formed component, due to subsequent remelting and heating effects, the ultrasonic effect was weakened, resulting in the disappearance of the nanocrystalline zone. Compared to I-UIT-WAAM S-UIT-WAAM samples samples, S-UIT-WAAM samples showed better ultrasonic assistance effects due to the ultrasonic impact on the molten pool, with significantly reduced austenite content, average grain size, and texture density. In terms of mechanical properties, for S-UIT-WAAM samples, the horizontal tensile strength was 1401.3 ± 57.6 MPa, and the vertical tensile strength was 1327 ± 9.5 MPa. Compared to directly deposited specimens, the horizontal and vertical tensile strengths of I-UIT-WAAM samples increased by 14.6% and 11.3%, respectively.

Keywords

• 18Ni-300 Martensitic aging steel
• ultrasonic impact treatment
• additive manufacturing
• microstructure
• mechanical properties