等离子喷涂8YSZ涂层在铝熔体作用下热冲击行为的数值模拟

Numerical Simulation of Thermal Shock Behavior of Plasma Sprayed 8YSZ Thermal Barrier Coatings Subjected to Molten Aluminum

目的定量理解等离子喷涂8YSZ热障涂层浸入铝熔体中的热冲击行为。方法基于热-力耦合计算方法有限元数值模拟,研究等离子喷涂8YSZ热障涂层浸入铝熔体时涂层中的瞬态温度场和瞬态应力场,以及涂层预热温度、陶瓷层厚度对应力分布的影响。结果温度场计算表明,在涂层浸入铝熔体0.1 s时,涂层表面就达到了铝熔体温度。随着涂层浸入铝熔体的时间增加,涂层内的温度分布逐渐由指数分布转变为近线性分布,而且涂层内的温度梯度也随着时间的增加而减小。相应涂层中的应力在相当短的时间内就达到了最大值,并随着加热时间的增加,最大应力值逐渐减小。涂层预热温度越高,在陶瓷层中的轴向应力和环向应力均越小,预热温度对轴向应力的影响更加明显。随着陶瓷层厚度的增加,陶瓷层内的轴向应力和环向应力值均增加,粘结层内的轴向应力和环向应力值均减小。结论对热障涂层进行预热处理可以有效降低涂层中的热应力值。涂层厚度增加,陶瓷层内应力随之增加,粘结层内应力随之减小,且陶瓷层厚度对粘结层中的应力影响更加明显。

The work aims to deeply understand the thermal shock behavior of plasma sprayed 8YSZ thermal barrier coating subjected to molten aluminum. Finite element numerical simulation was carded out by thermal-mechanical coupling method in transient temperature field and transient stress field when the plasma sprayed 8YSZ thermal barrier coating was immersed in molten aluminum, and effects of preheating temperature and thickness of top coat on stress distribution were studied. Through calculation of temperature field, the coating surface temperature reached up to a molten aluminum temperature as the coating was immersed into the molten aluminum for only 0.1 s. Temperature distribution in the coating changed gradually from exponential distributions to nearly linear distributions as the immersion time increased, but, the temperature gradient in the coating decreased as the immersion time increased. The stress in corresponding coating reached up to the maximum in a short time and the maximum stress decreased as the heating time increased. As preheating temperature of the coating increased, both the max- imum axial stress and the maximum hoop stress in the top coat decreased, and effects of the preheating temperature on the axial stress became more obvious. As the top coat thickness increased, the axial stress and the hoop stress in the top coat increased accordingly, but all the stresses decreased in the bond coat （BC）. The preheating treatment to thennal barrier coating can effectively reduce the thermal stress value in the coating. As the coating thickness increases, the stress in top coat and bond coat respectively increases and decreases and the effect of top coat thickness on stress in bond coat is more obvious.