超音速激光沉积Ti-6Al-4V合金结合界面特征数值模拟及试验验证

目的探究超音速激光沉积(SLD)过程中激光辐照温度和颗粒撞击速度对Ti-6Al-4V合金结合界面特征的影响规律,并通过试验对数值模拟结果进行验证。方法基于Johnson-cook材料模型,利用ABAQUS 2017软件并采用欧拉-拉格朗日耦合CEL(Coupled Euler-Lagrange)计算模型和Lagrange计算模型,进行Ti-6Al-4V单颗粒和多颗粒的撞击行为数值模拟,并结合超音速激光沉积试验验证模拟结果。采用扫描电镜(SEM)和光镜(OM)对涂层的界面结合特征进行观察和分析。结果单颗粒撞击温度场模拟结果表明,当激光辐照温度为1073 K时,随着撞击速度的增加,颗粒界面结合温度不断升高。当撞击速度为800 m/s和900 m/s时,颗粒与基体局部最高温度分别为1876.7 K和1874.8 K,界面发生微熔。800 m/s时,颗粒压缩率为34.3%,扁平率为1.27,有效塑性应变为2.6,基体的凹坑深度为7.88μm,该参数下的超音速激光沉积涂层界面结合良好。多颗粒撞击温度场模拟结果表明,当撞击速度为800 m/s时,随着激光辐照温度的升高,孔隙逐渐减少。激光辐照温度为1073 K时,颗粒撞击界面的温度高达3463.7 K,但颗粒内部的温度还未达到熔点并保留在1073~1676.8 K。随着激光功率的升高,钛合金涂层的孔隙率降低为0.67%(SLD 700W),约为同条件下CS涂层孔隙率(8.31%)的1/12。结论激光辐照的热能使颗粒与基体以及颗粒间界面处的温度达到了材料熔点,实现颗粒表面微熔形成冶金结合。冷喷涂Ti-6Al-4V涂层中,颗粒与基体以及颗粒间均存在明显的孔隙,超音速激光沉积Ti-6Al-4V涂层颗粒与基体以及颗粒间的界面结合良好,试验结果与数值模拟结果大致吻合。

Numerical Simulation and Experimental Verification of Interfacial Bonding Behavior of Ti-6Al-4V Alloy via Supersonic Laser Deposition

The work aims to investigate the effects of laser irradiation temperature and particle impact velocity on the interfacial bonding characteristics of Ti-6Al-4V particles in the Supersonic Laser Deposition(SLD),and verify the numerical simulation results by experiments.Based on Johnson cook material model,coupled Euler Lagrange Model and Lagrange model were used to simulate the impact behavior of single and multiple Ti-6Al-4V particles by ABAQUS 2017 software,and the simulation results were further verified via supersonic laser deposition technology.The interfacial bonding characteristics of the coating were observed and analyzed by Scanning Electron Microscopy(SEM)and Optical Microscope(OM).The simulation results of the temperature field for single particle impact showed that the interfacial temperature of particles increased with the increase of impact velocity when the laser irradiation temperature was 1073 K.When the impact velocity was 800 m/s and 900 m/s,the local maximum temperature of particles and matrix was 1876.7 K and 1874.8 K respectively,and micro melting occurred at the interface.When the impact velocity was 800 m/s,the compression rate of particles was 34.3%,the flattening rate was 1.27,the effective plastic strain was 2.6,and the crater depth of matrix was 7.88μm.Therefore,a good interfacial bonding was achieved under such conditions.It was found by simulating the temperature field of multi-particles impact that when the impact velocity was 800 m/s,the pores gradually decreased with the increase of laser irradiation temperature.When the laser irradiation temperature was 1073 K,the temperature of particle impact interface reached 3463.7 K,but the temperature inside the particle did not reach the melting point and remained at 1073~1676.8 K.With the increase of laser power,the porosity of titanium alloy coating decreased to 0.67%(SLD 700 W),which was 12 times lower than that of CS coating(8.31%).The thermal energy of laser irradiation makes the interfacial temperature between particles and matrix as well as the interfacial temperature between particles reach the melting point of materials,and realize the micro-melting on the surface of particles,thus resulting in metallurgical bonding.There are obvious pores between the particles and the matrix in the cold spray coating,but in the Ti-6Al-4V coating by supersonic laser deposition,the interface between the particles and the matrix is well bonded.The experimental results are in good agreement with the numerical simulation results.