Investigation of thermal shock resistance of CeO2 coating on Titanium alloy by magnetron sputtering 2019-28-0103
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 have been proposed as TBC, due to their high thermal expansion coefficient, higher thermal shock resistance, good adhesion strength, low corrosion rate and excellent tribological performance. In this study, CeO2 were coated on Titanium alloy by magnetron sputtering by varying the deposition time. The microstructure and mechanical properties of CeO2 coatings were systematically investigated. Deposition time was varied as 30 mins, 60 mins and 90 mins respectively, to achieve the variation in thickness of the coating on the substrate. The thickness of the coated specimen was measured by atomic force microscopy and found to be 500 nm, 180 nm and 70 nm respectively. Surface roughnesses of the coated surface are 152.28 nm, 86.25 nm and 18.65 nm. The Vickers hardness was found to increase with increasing amount of CeO2. Corrosion ability of the coated specimen was identified by using electrochemical corrosion resistance test. The coating with a lower concentration of particles has the best corrosion properties. Higher concentration of particles increased the defects density in the coating which has a negative effect on the corrosion resistance. Thermal shock resistance / thermal cycling test was carried out on the coated specimens at 800oC. Testing samples are visually inspected for evidence of spallation at every 10 cycles. This test is completed at 100 cycles. The thermal cycling numbers are recorded as thermal cycling life of TBC coating. CeO2 could be used as a promising material for excellent thermal cycling behavior and corrosion protective layers in titanium alloy aircraft infrastructures.