表面技术2025，Vol.54Issue(9)：138-151,14.DOI:10.16490/j.cnki.issn.1001-3660.2025.09.012
TiNbZr难熔中熵合金激光熔覆过程温度场和流场模拟
Simulation of Temperature and Flow Fields in Laser Cladding Process of TiNbZr Refractory Medium-entropy Alloy
摘要
Abstract
Laser cladding of refractory alloys on titanium alloy surfaces has the potential to enhance surface properties,expanding applications under high-temperature and wear-intensive conditions.By precisely controlling energy distribution and melt pool dynamics,laser cladding can improve the solidification characteristics and compositional distribution of coatings.However,due to the complexity of the rapid melting and solidification process,real-time monitoring of melt pool behaviors is challenging,making numerical simulation an essential tool for investigating melt pool evolution. In this study,a numerical simulation with experimental validation is integrated using the COMSOL Multiphysics platform to develop a three-dimensional finite element model that incorporates heat transfer,fluid dynamics,and free surface movement in the laser cladding process.This model simulates the cladding of TiNbZr refractory medium-entropy alloy onto a TC4 titanium alloy substrate.Comparing the model with experimental results shows an average deviation of 5.15%and a maximum deviation of 8.88%in key forming parameters such as clad height,width,and depth,validating the model's accuracy,with peak temperatures exceeding 2 500 K and maximum flow velocities reaching 257 mm/s. The analysis on the effects of the laser heat source,convective heat transfer,radiative heat loss,and substrate heat conduction on the melt pool temperature field and profile indicates that heat conduction within the substrate is the primary mode of heat loss in the laser cladding process.The further analysis on the solidification interface shows that from the bottom to the top of the melt pool,the morphology parameter(G/R)gradually decreases,while the cooling rate(G×R)increases,confirming the transition in solidification microstructures from planar to columnar to equiaxed grains,along with a reduction in grain size observed in physical experiments.The quantitative analysis of the melt pool's surface temperature field,velocity field,surface tension,and Marangoni forces demonstrates that although the flat-top laser source provides a more uniform energy distribution,its unique edge effects cause significant variations in the melt pool temperature,Marangoni force,and surface tension at the edges of the laser spot.These variations lead to accelerated melt flow in these regions.According to findings in comparing the roles of different forces within the melt pool,it is evident that Marangoni forces and surface tension govern the liquid surface morphology.Outward-directed Marangoni forces pull molten material toward the edges of the melt pool,resulting in a depression.Finally,the elemental analysis combined with physical experiments shows that Marangoni convection creates inflection points in the flow field at the sides and the bottom of the melt pool,obstructing element mixing.This results in the segregation of V elements from the substrate at the center of the melt pool and Zr elements from the powder at the upper edge,leading to macrosegregation that affects coating performance. Overall,the quantitative assessment of temperature and velocity fields from both numerical simulations and physical experiments reveals that heat conduction in the laser melt pool significantly influences the solidification morphology of the coating.Additionally,the unique energy distribution of the flat-top laser source affects mass transfer within the melt pool,further impacting the compositional distribution of the coating.关键词
激光熔覆/数值模拟/激光熔池/温度场/流场模拟Key words
laser cladding/numerical simulation/laser melt pool/temperature field/flow field simulation分类
航空航天引用本文复制引用
陈育钒,刘晋,刘艳,胡登文,杨川,王雷..TiNbZr难熔中熵合金激光熔覆过程温度场和流场模拟[J].表面技术,2025,54(9):138-151,14.基金项目
国家自然科学基金(5237053678) National Natural Science Foundation of China(5237053678) （5237053678）
