等离子喷涂过程基体温度场分布的数值模拟

Numerical Simulation on Temperature Distribution of Substrate During Plasma Spraying

等离子喷涂的热源温度高,涂层成形区域温度梯度大、热量累积快,涂层中常存在较大的残余应力。研究通过数值模拟并辅以必要的试验测试研究了等离子喷涂过程基体表面热量累积行为:建立了二维静态喷枪加热模型,研究了在不同喷涂距离时基体表面温度场分布规律;建立了移动热源加热模型,研究了在不同喷枪移动速度和扫描遍数时基体热量累积规律。结果表明:在静态喷枪加热作用下,基体温度场呈中间高两端低的对称分布状态;随着喷涂距离减小,基体表面最高温度与平均温度显著升高,温度梯度变化明显,高温区域半径显著增大。在动态喷枪加热过程中,基体左右边界热量累积现象明显,且喷枪移动速度越快,基体表面热量累积越少,温度分布梯度越小;随着喷枪扫描遍数的增加,基体中心区域温度呈波浪式上升,温度增长幅度逐渐变小。

The temperature of heat sources is high during plasma spraying. Coating forming area has the feature of large temperature gradient and fast heat accumulation, therefore, large residual stress is often induced by this factor in coatings. The numerical simulation and experimental measurement were implemented to investigate the heat accumulation behavior on the substrate surface during plasma spraying. A 2 D model of static heating model was established by numerical simulation, and the temperature distribution was studied at different spraying distances. The moving heat model was established and the heat accumulation was studied at different moving speeds and scanning numbers. The results show that the subsrate temperature presents symmetrical distribution. The temperature in the middle is high and the two sides are low in the static heating model.With the decrease of spraying distance, the maximum and average temperature significantly increases. The temperature gradient also significantly changed, and the radius of the high-temperature region increases. In the move heating model, the heat accumulation is obvious at the left and right boundaries of the substrate. The faster the spray gun moves, the less heat accumulation and the smaller temperature gradient on the substrate. With the increase of the scanning number of the spray gun,the temperature in the central region rises in a wavy manner and the temperature increment gradually declines.