Solidification Structure Evolution and Temperature Field Study of Iron-based Alloys with Synchronous Powder-feeding Underwater Laser Additive
To address the requirements for surface damage repair and underwater in-situ remanufacturing of iron-based structural materials prevalent in the marine environment,this paper implemented a coaxial powder-feeding submerged laser additive manufacturing(SUAM)technology using a layer-by-layer molding method.Due to the unstable temperature gradients from multiple heat inputs,the grain growth in the upper region of the additive structure resembles that of a planar coating,with no distinct columnar grains in the region close to the substrate.EBSD results show that the grain size and dislocation density changed between the additive interface,and epitaxial growth phenomenon occurs,and a periodic fine-grained band appears in the middle of the block,and the average hardness of the fine-grained band is 805 HV0.025,while the hardness of the larger equiaxed grain zone is 770 HV0.025.Further the temperature field of the SUAM laser heating process was obtained using numerical simulations by introducing a protective air and boiling model.The maximum temperature of underwater laser heating is about 16％lower than that in air,and the boiling model has no effect on the temperature distribution.This study provides theoretical support for for advancing the development and application of SUAM.
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