The underwater laser cladding layers of Ti-6Al-4V titanium alloy were prepared using underwater wire-feeding laser cladding (UWLC) technology under different heat inputs and gas flow rates. At optimum process parameters, the uniform underwater cladding layer without oxidation was obtained, and the cracks inside layer were restrained successfully. The deposition morphology, grain characteristics, microstructure and properties of the cladding layer were analyzed, and the mechanism of crack elimination was investigated. With the increase of heat input, the grain size and thickness of the α lath increased, while the amount of α' decreased, and the oxidation phenomenon had also improved. The sizes of columnar β-crystal grains and spherical β-crystal grains both increased. The microstructure of the different heat input layers was composed of lamellar α phase and acicular α′ phase with different sizes. Besides, the reduction of the cooling rate inhibited the unidirectional growth of acicular martensite, so that the martensite arrangement was close to a disordered state, and the deformation of the cladding layer was more uniform, which effectively prevented the cracks and melt expansion. The corrosion resistance of the coating was improved, and the microhardness was reduced.

采用水下送丝激光熔覆（UWLC）技术在不同热输入和气体流量下制备Ti-6Al-4V钛合金水下激光熔覆层。在最佳工艺参数下，获得了均匀无氧化的水下熔覆层，并成功抑制了层内裂纹。分析了熔覆层的沉积形貌、晶粒特征、显微组织和性能，研究了裂纹消除机制。随着热输入的增加，α板条的晶粒尺寸和厚度增加，而α'的量减少，氧化现象也有所改善。柱状β-晶粒和球形β-晶粒的尺寸均增大。不同热输入层的微观结构由不同尺寸的层状α相和针状α'相组成。此外，冷却速度的降低抑制了针状马氏体的单向生长，使马氏体排列接近于无序状态，熔覆层的变形更加均匀，有效地防止了裂纹和熔体膨胀。涂层的耐蚀性提高，显微硬度降低。