钛合金基体EB-PVD热障涂层的制备与初步研究

Preparing and Study of EB-PVD Thermal Barrier Coatings on Titanium Substrates

在TC11钛合金上制备两种以NiCoCrAlY为粘结层,8wt%Y2O3-ZrO2(YSZ)为陶瓷层的热障涂层,粘结层制备技术分别为电子束物理气相沉积(EB-PVD)和超音速火焰喷涂(HVOF),陶瓷层由EB-PVD同炉沉积。两种热障涂层的微结构、显微硬度及热循环测试表明,EB-PVD制备的粘结层均匀致密,上层YSZ组织细密,硬度较高,而HVOF获得的粘结层疏松不均,上层YSZ晶粒粗大,硬度较低;前者有较好的抗热冲击性能,裂纹较分散,防护性能较好,而后者易开裂剥落,裂纹密集,防护性能较差。

Two kinds of thermal barrier coatings with NiCoCrAlY bond coatings deposited by electron beam-physical vapor deposition （EB-PVD） and high velocity oxy-fuel thermal spraying （HVOF）, respectively, as well as 8wt% Y2O3-ZrO2 ceramic layers deposited in one batch by EB-PVD were prepared on near-α titanium alloys. The field emission scanning electronic microscopy and microhardness indentation were used in comparatively study of microstructures, microhardness of samples. Cracking modes and crack characteristics in TBCs were investigated after thermal cycling in atmosphere, along with the discussion of roles of residual stresses, bonding strengths and mechanical properties of bonding coats in different failure extents. It is found that morphologies of BCs deposited by different methods （EB-PVD and HVOF） resulted in the different microstructures and microhardness of their upper YSZ. The denser and more homogeneous BC prepared by EB-PVD led to the YSZ with slim and dense columnar clusters and higher microhardness, and the inhomogeneous and porous latter resulted in the upper YSZ with coarse and loose bonded columnar grains and lower microhardness, and the TBC with BC deposited by EB-PVD was more protective, which was synthetically induced by residual stresses, bonding strengths and mechanical properties of bonding coats.