CAJ | 학술논문

激光熔覆时熔池对流运动对熔覆层成分和气孔缺陷分布具有较大影响。通过在灰铸铁和45钢两种基体上进行激光熔覆NiCuFeBSi系合金的工艺试验，对熔池的对流运动形式进行了机理分析与试验验证。结果表明，受熔池强对流运动影响，熔覆层气孔呈均匀弥散化分布趋势；且自熔覆层底部向顶部方向合金元素分布均匀，无缓慢过渡特征。根据YAG激光光斑能量的高斯分布特征，获得了熔池对流运动的驱动力是熔池温度分布不均形成的熔池表面张力梯度。而且熔池表面张力梯度与激光能量密度，熔池温度，熔体对流运动速度是彼此密切相关的。熔池对流运动机理分析表明，热流密度越高，温度越高，表面张力梯度越大，熔体对流运动速度越大。
격광용복시용지대류운동대용복층성분화기공결함분포구유교대영향。통과재회주철화45강량충기체상진행격광용복NiCuFeBSi계합금적공예시험，대용지적대류운동형식진행료궤리분석여시험험증。결과표명，수용지강대류운동영향，용복층기공정균균미산화분포추세；차자용복층저부향정부방향합금원소분포균균，무완만과도특정。근거YAG격광광반능량적고사분포특정，획득료용지대류운동적구동력시용지온도분포불균형성적용지표면장력제도。이차용지표면장력제도여격광능량밀도，용지온도，용체대류운동속도시피차밀절상관적。용지대류운동궤리분석표명，열류밀도월고，온도월고，표면장력제도월대，용체대류운동속도월대。
The molten pool convection has a great impact on elements and pores distribution during the laser cladding process. In this paper, the form of molten pool convection was investigate in terms of laser cladding NiCuFeBSi alloys on the substrate of gray cast iron and 45 steel. Results indicated that the distribution forms of pores and elements in the clad layer are uniform and dispersive due to the molten pool convection. Moreover, element distribution is also uniform without any slow transition from the bottom of clad layers to the top by means of electron probe microanalysis (EPMA). And according to the Gaussian distribution of energy in the YAG laser beams, it can be concluded that the driving force of convection is the surface tension gradient due to the non-uniform distribution of molten pool temperatures. Those of the laser thermal density, the molten pool temperature, the convective speed and the surface tension gradient are closely related with each other. It indicates that the temperature increases as the laser thermal density rising. The higher temperature is, the larger surface tension gradient will be as well as the convective speeds.