Corrosion Behaviour of Plasma Sprayed Alumina and Yttria Stabilised Zirconia Composite Coatings Applied on Al6061Substrate

Publication Type:

Miscellaneous

Source:

Journal of Material Science and Manufacturing Technology, Volume 3, Issue 1, p.911–930 (2018)

URL:

http://mantechpublications.com/admin/index.php/JoMSMT/issue/viewIssue/911/1012

Keywords:

Department of Mechanical Engineering

Abstract:

In this investigation, hot corrosion test was conducted on Plasma sprayed Yttria stabilized zirconia and alumna composite coatings applied on Al6061 substrate. The specimens were prepared using aluminium self bonding composite powder as first bond coat and alumina-Nickel cermet as second bond coat. The top coat comprises the mixture of alumina and Yattria Stabilised Zirconia in 50:50 proportions. In the corrosion test, molten salt blends of 55 wt. % V2O5+45wt. %Na2SO4 was taken as corrosive environment and this blend was spread on the top coat of the specimens. The spread molten salt specimens were kept in the furnace at 350°C for 40 hours. After the test, specimens were subjected to scanning electron microscopic and X-Ray Diffraction Analysis. From the results, it was observed the development of YVO4 crystals and monoclinic ZrO2 were the hot corrosion products. The phase change of stable tetragonal ZrO2 to unstable monoclinic ZrO2 degraded the coating surface and led to spallation. It was also observed that the specimen of 100µm top coat thickness has developed bigger cracks compared to that of specimens with 200µm and 300µm top coat thickness. It was clearly evident that bond coat was severally attacked by the hot corrosion process which also led to the spallation of coating from the substrate