Temperature-dependent and duration-dependent effect on the growth behavior of CVD aluminide coating on K452 superalloy

Aluminide coatings on the K452 alloys were fabricated in this study by chemical vapor deposition (CVD) under various deposition temperature and duration aiming to investigate the growth behavior of aluminide coating. The microstructure and phase evolution of aluminide coating were discussed in detail. Results showed that the outer layer (OL) consisting of 8-NiAl, and the inter-diffusion layer (IDL) comprised of carbides and topologically close packed phases TCP (Cr3(Ni, Co)2) were formed in all specimens. In addition, another whisker precipitation phase can be found in aluminized specimens deposited at 850 degrees C, 900 degrees C and 950 degrees C, and finally transformed into Cr3(Ni, Co)2 phase by further promoting the deposition temperature. As for the specimens deposited for various duration, the content of TCP in the specimens deposited at 1050 degrees C showed a decreasing trend with the increase of the deposition duration, and the opposite for carbides. Based on these results, the growth behavior of CVD aluminide coating on K452 superalloy was proposed comprehensively. The results of this study can provide a guidance for preparation of high-performance CVD aluminide coating on K452 superalloys.