"Formation of Functional Gradient Zirconia Coating by Gas Tunnel Type Plasma Spraying"

采用风洞式等离子喷涂技术制备了氧化锆功能梯度涂层。通过实验阐明了该涂层的特性，并对涂层的形成过程进行了探讨。研究结果如下：（1）在短距离喷涂中，气体隧道式等离子喷涂获得了高硬度的氧化锆涂层，与氧化铝涂层的情况相同。例如，在P=26kW，L=30mm时，表面层的维氏硬度为Hv=1100。该层具有比常规型等离子喷涂更高的耐磨性。(2)从高硬度氧化锆涂层的横截面结构来看，涂层表层的孔隙数量少于内层。涂层横截面上维氏硬度分布的测量结果表明，氧化锆涂层在厚度方向上具有梯度功能。(3)研究了氧化锆涂层在厚度方向上的磨损特性。然后，在高硬度表面层的磨损量很小，但向涂层内部增加。因此，这种氧化锆涂层在厚度方向上的梯度功能被证明是作为磨损特性以及硬度特性。(4)从理论上探讨了气体隧道式等离子喷涂涂层的形成机理。通过对氧化锆涂层形成过程的计算机分析，解释了涂层在厚度方向上的梯度功能。

In this study, the functional gradient zirconia coating was formed by a gas tunnel type plasma spraying. Then the characteristics of this coating were clarified experimentally and the formation process of the coating was discussed. The results obtained are as follows :(1) In a short distance spraying, a high hardness zirconia coating was obtained by the gas tunnel type plasma spraying as well as the case of alumina coating. For example, the Vickers hardness in the surface layr was Hv=1100 at P=26kW,L=30mm. This layr had a higher wear resistance than that of the conventional type plasma spraying.(2) According to the structure of cross section of high hardness zirconia coating, the amount of pore in the surface layr was less than that of inside layr of this coating. And the result of the measurement of Vickers hardness distribution in the cross section showed the gradient functionality of this zirconia coating in the thickness direction.(3) The wear characteristic of this zirconia coating in the thickness direction was also investigated. Then, the wear weight in that high hardness surface layr was very small, but increased towards inside of the coating. Thus the gradient functionality of this zirconia coating in thickness direction was proved as to the wear characteristic as well as the hardness characteristic.(4) The formation mechanism of sprayd coating by gas tunnel type plasma spraying was discussed theoretically. And then the gradient functionality of this zirconia coating in the thickness direction was explained from the result of computer analysis about the formation process of this coating.