|
Zirconia ceramics has high melting point, small density, low thermalconductivity and thermal expansion coefficient, which is close to the hightemperature alloy. Therefore it has become the first choice of thermal barrier coatingmaterials. In this paper, a high adhesion strength zirconia ceramics film is preparedon GH4141. To achieve this goal, EB-PVD and vacuum heat treatment are used andhigh temperature active solder is also used to improve the adhesion between theceramic coating and metal substrate．In order to explore the influence of solder composition on the performance ofthe membrane, three different solders are used. After a series of tests, we found thatthe solder with composition Ti-31.171wt.%, V-68.600wt.%, Cr-0.232wt.%performed best.EB-PVD has led to a small range migration of the elements, which results in arelatively thin transition region, so the adhesion strength is weak. To promote thespread of elements and interface reaction, subsequent heat treatment is necessary. Inthis experiment, we set holding time as20minutes, different heat temperature areset as1200°C and1300°C respectively. The result shows that: higher temperaturecan lead to longer diffusion path and greater extent of the transition.Because the thickness of the composite plating is in microns, and thermalexpansion coefficient differences exist between metal and ceramics. So heattreatment can not only promote the spread of elements, but also lead to interfacestress. The film adhesion is influenced by both of them. When the heat temperatureis1300°C, the surface of the membrane layer wrinkled, indicating that too hightemperature has a bad influence. When the heat temperature is1200°C, we achievedhigher adhesion and well-looking surface morphology. So1200°C is suitable.Through the research project, we find that, micron grade membrane layerthickness, decided that, during the diffusion process, they will have a differentperformance from the work piece with big size. Firstly, electron beam depositionresults in small distance between the connected specimens, and small range ofmigration is enough to realize their connection. But a thinner thickness results in asmaller strength of the membrane, once the interface stress are produced during theconnection process, they are more likely to lead to interface cracks.
|