Investigation of Thermal Shock Resistance of CeO ₂ Coating on Titanium Alloy by Magnetron Sputtering

Titanium alloy (Grade V) is used in aerospace, medical, marine and chemical processing industries. To improve the thermal shock resistance and corrosion resistance of the titanium alloy at elevated temperatures, Thermal barrier coating (TBC) has been predominantly used. Cerium oxides (CeO₂) have been proposed as TBC, due to their high thermal expansion coefficient, higher thermal shock resistance and low corrosion rate. In this study, CeO₂ was coated on Titanium alloy by magnetron sputtering. Deposition time was varied as 30 mins, 60 mins and 90 mins respectively, to achieve the variation in thickness of coating. Thickness of the coated specimen was measured by atomic force microscopy and found to be 500 nm, 120 nm and 80 nm respectively. Surface roughness of the corresponding coated surfaces is 152.28 nm, 18.41 nm and 18.65 nm. The Vickers hardness was found to increase with decrease in coating thickness upto certain extent then decreases. Corrosion ability of the coated specimen was identified by electrochemical corrosion test. The coating with lower concentration of particles has the best corrosion properties. Thermal shock resistance test was carried out on the coated specimens at 800^oC for 20 minutes and allowed the samples to cool in atmospheric air for 20 minutes. The test was completed after 20 cycles. Spallation on the samples was identified by ultrasonic testing and found to be minimal on the coated sample having thickness of 120 nm. CeO₂ could be used as promising material for excellent thermal cycling behavior and corrosion protective layers in titanium alloy aircraft infrastructures.