喷涂距离对Fe基非晶涂层孔隙影响的研究

Spraying distance effect on the porosity of Fe-based amorphous coatings

热喷涂涂层中孔隙的存在会降低涂层的耐蚀性,减少涂层寿命,而热喷涂工艺参数很大程度上影响涂层的孔隙率。本文采用计算机数值模拟和设计验证实验的分析方法,重点研究了JP-8000超音速火焰喷涂系统(HVOF)制备Fe基非晶涂层工艺参数中喷涂距离与涂层孔隙的关联性。利用商用计算软件Fluent计算平台,研究加入粉末粒子前,喷枪内火焰温度和速度的变化规律,以及加入非晶粉末后,不同喷涂距离条件下颗粒飞行过程的温度和速度的变化规律。仿真结果表明,喷涂距离为360~380 mm时,非晶粉末颗粒在撞击基板时处于半融化状态,颗粒在基板上具有良好的流动性,可获得孔隙率较低的涂层。验证实验结果与仿真结果一致。X射线衍射结果表明,粉末、不同喷涂距离所制备的涂层以及同成分的非晶条带均为完全非晶态结构。SEM和孔隙率统计结果表明,喷涂距离为370 mm时,涂层截面的孔隙较少,且孔隙率最低,为0.57%,验证了计算模拟优化的最佳喷涂距离范围。

With the presence of porosity,the corrosion resistance of thermal spray coating can be reduced and the life of the coating can be shortened,while the thermal spray process parameters greatly affect the porosity of the coating.Therefore,the analytical method of computer simulation and design verification experiment was adopted to study the correlation between spraying distance and coating porosity in the process parameters of Fe-based amorphous coating prepared by JP-8000 high-velocity oxygen-fuel spray system(HVOF).The temperature and velocity change rules of the flame before the addition of the powder particles,and the temperature and velocity change rules of the particles during the flight process after the addition of the powder particles were investigated respectively using the commercial computing software Fluent.Simulation results show that when the spraying distance was at the range of 360~380 mm,the amorphous powder particles exhibited a semi-melting state at the time of the powder particles impacting the substrate,the particles had good fluidity on the substrate,and a coating with lower porosity could be obtained.The experimental results were consistent with the simulation results.X-ray diffraction results showed that the powders and the coatings prepared with different spraying distances as well as the ribbons of the same elemental composition were all amorphous structures.SEM images and porosity statistic results suggested that when the spraying distance was 370 mm,the coating had less porosity and the lowest porosity(0.57%),verifying the optimal spraying distance for the simulation results,which was of great significance for the preparation of Fe-based amorphous coatings with excellent performance.