热障涂层弹性模量和残余应力测试研究

Experimental measurement of elastic modulus and residual stress of thermal barrier coatings

采用数字图像相关法实验研究了热喷涂制作的热障涂层的弹性模量和残余应力。首先,采用三点弯测试方法对热障涂层试件进行加载,并利用二维数字图像相关方法对热障涂层试件加装过程中的弯曲变形进行了精确的测量,进而获得了热障涂层在受拉和受压两种状态下的弹性模量,结果表明,受拉时热障涂层试件陶瓷层的弹性模量为31GPa,而受压时其弹性模量为34GPa。其次,基于内力平衡,推导了考虑曲率变化的涂层残余应力计算公式;利用三维数字图像相关法测量了喷涂前后基体曲率的变化,进而获得了涂层残余应力的大小,结果表明,热喷涂后的热障涂层残余应力为压应力,大小为-86^-70MPa。

The elastic modulus and residual stress of thermal-sprayed coating are experimentally measured by the digital image correlation method.Firstly,three-point bending testing method is used to measure the elastic mudulus of thermal barrier coating specimens.Meanwhile,the 2 D digital image correlation method is employed to measure the bending deformation of the specimens.The elastic moduli of the coating in tension and compression stresses states are obtained.The results indicate that the elastic mudulus is 31 GPa when the ceramic layer is tensiled and 34 GPa when the ceramic layer is compressed,respectively.Secondly,a formula for calculating the residual stress of thermal barrier coating based on the internal force equilibrium and curvature change is deduced and the 3 D digital image correlation method is used to obtain the curvature change of the substrate before and after thermal spraying.Then,the residual stress of the coating specimens is calculated.The results demonstrate that the residual stress of thermal-sprayed coating is compressive with magnitude of-86^-70 MPa.