|
In this paper, the effect of increase Al diffusion rate in BC in the high-temperature oxidation(1100℃) process to improve the operating life of TBCs had been studied by theoretical analysis. as a supplementary means, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron microprobe, X-ray diffraction analysis (XRD) ect had been used.The results show that: APS thermal barrier coatings in high-temperature oxidation process mainly divided into three stages: the early stage of oxidation, and stability of stage, the final stage of the complex oxidation. In the early stage of oxidation, continuousα-Al2O3 film on the initial between BC and TBC has not formed, and oxidation speed is very fast, weight gain obviously, the oxidation kinetics curve of this stage obey straight law. With the oxidation reactions to continue, forα-Al2O3 film quickly formed, high-temperature oxidation entered the stable stage, the places of high-temperature oxidation in this stage is the BC-TGO interface, and the mode of high-temperature oxidation is selective oxidation about Al, oxidation speed is very slow, oxidation kinetics curve of this stage obey parabola law. With Al element in the large number of consumption in BC, eventually, poor Al phenomenon will appear at the interface of B-O, leading to the end of selective oxidation. The next process, due to the concentration of Al less than the standard of selective oxidation, and other metal elements which once again to the participation of high-temperature oxidation reactions, or even the nature of a stable of Ni has been generated NiO, while spinel type oxides at this stage a significant increase. During the course of high-temperature oxidation reactions of places is B-O interface, TGO gradually to the TBC is the direction of the manner in which formed, and the large number of spinel oxide is one of the reasons for TBCs failure in the early stage of oxidation and the final stage of the complex oxidation.Through the above analysis know: It can be beneficial to well-of Al in the high-temperature oxidation process by increase the diffusion speed of Al element in BC, advance into the stage of stability and delay the poor Al moment in the B-O interface. Therefore, this theory to guide the introduction of SSPB process, trying to improve the physical properties of coatings, and the increase Al diffusion rate in BC in high-temperature oxidation process, with a view to quickly enter into the stability stage at the same time to ensure the smooth progress of selective oxidation , Delaying the arrival of the poor Al moment, thereby inhibiting large number of spinel oxide production to improving coating life.The results showed that: coating particle size to a large extent affected the diffusion rate of Al in BC, and because of SSPB technology on the surface of coating, near the surface coating layer has been optimized, obviously, the diffusion ablity of Al element was increased in the BC.Contrast measured from the high-temperature oxidation kinetics curves know: It can be beneficial to well-of Al in the high-temperature oxidation process by addition of SSPB, advance into the stage of stability and delay the poor Al moment in the B-O interface. Of course , the coating after addition SSPB can enhance the life.
|