冷喷涂工艺参数对CoNiCrAlY涂层沉积影响

Effect of process parameters on cold spray deposition of CoNiCrAlY coatings

摘要:

采用数值模拟和试验研究相结合的方法，研究了冷喷涂工艺参数对CoNiCrAlY涂层微观结构和力学性能的影响．运用Ansys CFD软件建立了冷喷涂CoNiCrAlY高速射流场三维模型，系统研究喷涂气体种类、温度、压力及粉末粒径分布对粉末粒子温度和速度变化的影响规律．采用高压冷喷涂系统，在镍基高温合金GH625基体上沉积CoNiCrAlY涂层，利用光学显微镜观察CoNiCrAlY涂层的微观结构，并且利用ImageJ软件检测涂层的孔隙率，随后通过硬度计及拉伸试验检测涂层的显微硬度和结合强度．结果表明：随着气体温度升高粉末在喷枪出口处的温度及速度也升高，随着喷涂气体压力的升高粉末在喷枪出口处的速度增大，但是对气体压力的变化对粉末温度影响较小；在氮气气氛和1000 ℃条件下获得的冷喷涂CoNiCrAlY涂层的孔隙率为1.9%左右、结合强度约为57 MPa，在氦气气氛和700 ℃条件下制备的CoNiCrAlY涂层的孔隙率约为0.4%左右、结合强度超过70 MPa；经真空热处理后涂层的孔隙率与热处理前的相比，其孔隙率稍有降低；喷涂态CoNiCrAlY涂层的维氏显微硬度约为550 HV0.3, 热处理后CoNiCrAlY涂层的维氏显微硬度约为350 HV0.3，明显低于热处理前的显微硬度．

Abstract:

In this study， numerical and experimental methods were used to study the effects of cold spraying parameters on the microstructures and mechanical properties. Ansys CFD software was adopted to establish the 3D model of particle acceleration process and study the effects of gas type， temperature， pressure and powder particle size distribution on the temperatures and velocities of powder particles. Following that， CoNiCrAlY coatings were deposited on GH625 substrates by high pressure cold spray system. Optical microscopy was used to analyze the microstructures and ImageJ software was used to measure the porosity level of the CoNiCrAlY coatings. The results showed that the particle velocity and temperature increased with the increase of gas temperature. As the spraying gas pressure increased， the speed of the powder particle at the spray nozzle outlet was also higher， but the change of gas pressure had less effect on the particle temperature. Besides， the cold sprayed CoNiCrAlY coating obtained under the conditions of nitrogen and 1000 ℃ had a porosity of about 1.9% and a bonding strength of about 57 MPa. The porosity of the CoNiCrAlY coating prepared at 700 ℃ using helium gas was about 0.4%， and the bonding strength exceeded 70 MPa. The porosity of the coating after the vacuum heat treatment was slightly lower than that before the heat treatment. The Vickers microhardness of the sprayed CoNiCrAlY was about 550 HV0.3， and it was about 350 HV0.3 after vacuum heat treatment， which was significantly lower than that of as-sprayed coating.