摘要
大气等离子喷涂制备的LaMgAl_(11)O_(19)(LMA)热障涂层无定型相含量较高,会严重影响涂层服役寿命。通过900~1600℃不同温度热处理12 h,研究晶粒尺寸和孔隙率等微观结构和无定形相含量对LMA涂层力学、热物理以及抗热震性能的影响。结果表明:喷涂态LMA涂层具有900和1163℃两个结晶温度点。900℃热处理后,LMA涂层中含有较多的无定形相以及最高的孔隙率((18.88±2.15)%),1000℃测试时,具有最低的热扩散系数(0.53 mm^(2)/s);由于重结晶和烧结作用使得无定型相含量和孔隙率降低,1100~1400℃之间热处理的涂层具有较高的硬度(1100℃时达到最高值(12.08±0.58)GPa);1300℃热处理的涂层中含有大量微米级片状晶,具有较高的应变容限以及平均热循环寿命(588次);热处理温度达到1500℃时,由于片状晶平行堆叠,晶粒厚度迅速增加,孔隙率增加,力学性能显著降低。热震过程中由于热应力的反复作用,涂层内出现晶粒破碎和裂纹扩展等现象,导致涂层最终失效。
LaMgAl_(11)O_(19)(LMA)coating prepared by atmospheric plasma spraying has large amounts of amorphous phase,which seriously affects the service life of coating.Effects of microstructure,such as grain size,porosity and amorphous phase content,on mechanical,thermophysical and thermal shock resistance properties of LMA coatings after heat-treatement at 900–1600℃for 12 h were investigated.The results show that the as-sprayed LMA coating possesses two crystallization temperature points,900 and 1163℃.After heat-treatement at 900℃,the lowest thermal diffusivity of 0.53 mm^(2)/s was obtained for LMA coating at 1000℃due to the large amount of amorphous phase and the highest porosity of(18.88±2.15)%.LMA coatings,heat-treated at 1100–1400℃,exhibited higher hardness owing to reduced amorphous content and porosity through recrystallization and sintering with the maximum hardness of(12.08±0.58)GPa at 1100℃.After heat-treatement at 1300℃,the coating displayed the highest average thermal cycling life(588 times),which was attributed to abundant micron flake crystals with high strain tolerance.When the heat-treatment temperature reached 1500℃,the grain thickness increased rapidly due to parallel stacking of lamellar crystals,porosity increased and mechanical properties significantly decreased.During the thermal shock,grain breaking and crack propagation occurred in the coating due to the repeated thermal stress,resulting in final failure of the coating.
作者
安文然
黄晶琪
卢祥荣
蒋佳宁
邓龙辉
曹学强
AN Wenran;HUANG Jingqi;LU Xiangrong;JIANG Jianing;DENG Longhui;CAO Xueqiang(State Key Laboratory of Silicate Materials for Architectures,Wuhan University of Technology,Wuhan 430070,China)
出处
《无机材料学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第9期925-932,共8页
Journal of Inorganic Materials
基金
国家自然科学基金重点项目(92060201)。
