涂层结构设计对等离子喷涂陶瓷层结合强度及莫应力的影响

EFFECT OF LAMINETED DESIGN ON THE BOND STRENGTH AND STRESS OF PLASMA SPRAYED COATINGS

用等离子在４５＃碳钢上喷涂了不同涂层设计的Ａｌ２Ｏ３以及Ａｌ２Ｏ３＋１３０ｍｇ·ｇ－１ＴｉＯ２陶瓷层．用Ｘ－射线衍射法和拉伸实验测量了涂层表面层中的残余应力及结合强度．增加粘结层和过渡层能大大地克服陶瓷涂层与基材机械的以及热的不匹配性，使涂层的应力和结合强度都得到明显改善．此外，ＳｉＯ２能改善ＺｒＯ２陶瓷层与基材以及陶瓷层内部的结合程度，使涂层内应力松弛并使其结合强度提高．然而ＳｉＯ２添加剂只有在高熔点陶瓷层中（如ＺｒＯ２），＂液相烧结＂作用才明显，而在熔点较低的陶瓷层中（如Ａｌ２Ｏ３），这种作用并不明显．在用等离子喷涂低熔点Ａｌ２Ｏ３陶瓷时，添加适量的低熔点ＴｉＯ２陶瓷是必要的．

The laminated coatings of Al2O3-NiCrAl and Al2O3+130mg· g-1TiO2-NiCrAl were deposited on medium carbon steel substrates by plasma spraying.The bond strengths of the coatingS were measured by tensile adheSion bond tests, and the residual stresses in the outermost surfaCe layals were measured byX-ray diffraction. The bond and transition layers in the laminated coatings can largely overcome the inherent mechanical and thermal incompohbilities between the chide coating and metal substrate, therefore theresidual stress can largely be relaxed and the coatings would POssess good bond strength. On the other hand,when an appropriate additive is doped into refractory ceramic coatings, such as ZrO2, contact between ceramic and substrate as well as within coating would be developed. Thus the bond strength and the stress can befurther improved. Introduction of additive results in liquid phase sintering. The effeCt of additive of lowermelting point would be very obvious in the system which POssesses higher melting POint, such as theSiO2-doped ZarO2 coating. However, the effeCt would not be so aPParent in ceramic coatings which possesslower melting point, such as Al2O3 and Al2O3+130mg· g-1TiO2 systems. However, the introduction ofadditive TiO2 is necessary for spraying Al2O3 ceramic coating.