Study On High Temperature Corrosion Resistance Of Cylindrical 7YSZ Coating Prepared By PS - PVD

Thermal Barrier Coating with excellent insulation properties is also known as heating insulating coating, and it can also increase the operating temperature and corrosion resistance of the turbine engine hot section components. At the same time, TBCs can also extend the service life of hot section components. Currently, thermal barrier coatings are widely used in the surface of the hot section of aviation engine. Thermal Barrier Coating, high temperature alloy technology and high efficiency air-cooled technology are the three key technologies in the aspect of advanced aircraft engine blades.Under the influence of high temperature oxidation, hot corrosion, abrasion, impact and other factors, the work environment and failure behaviors of TBC is extremely complex. With aviation turbine engine towards a high thrust to weight ratio, high combustion efficiency direction, the combustion chamber temperature of turbine engine is becoming more and more high, CMAS (CaO-MgO-Al2O3-SiO2, CMAS) that deposited on the blade surface of turbine engine melt infiltration and fill the coating, which lead to coating spalling failure during ultra-high temperature thermal cycling. Serving as the turbine engine temperature rising, CMAS corrosion is more and more serious, TBCs cause many scholars’attention.In this paper, NiCoCrAlYTa bond coating was deposited on the surface of the nickel-based superalloy K417 by low pressure plasma spraying (LPPS). The layered APS 7YSZ coating was prepared by atmospheric plasma spraying (APS), and columnar PS-PVD 7YSZ coating was prepared by plasma spraying-physical vapor deposition (PS-PVD). The CMAS was prepared by drying-powder sintering process, using atmospheric plasma spraying deposited a thin layer of molten CMAS on the surface of 7YSZ coating. Using RZ-012A thermal shock testing machine, this paper also study the property resistance to CMAS corrosion of 7YSZ coating, test thermal shock resistance property of PS-PVD 7YSZ coating under CMAS environment. And study the damage failure mechanism of environmental sediments CMAS on the columnar PS-PVD 7YSZ coatings, which prepared by plasma spraying-physical vapor deposition.After CMAS corrosion for different times, the microstructure, element distribution, phase composition changes of 7YSZ thermal barrier coatings and 7YSZ coatings with CMAS deposited after thermal cycling for different times were analyzed by SEM, XRD, EDS. The experimental results are as follows:(1) CMAS powder that prepared by spray drying and vacuum sintering has high sphericity and uniform particle size distribution, which is suitable for plasma spraying.(2) After CMAS was deposited on the surface of 7YSZ coating and corrosion of different time, the layered APS 7YSZ coating occurs 7YSZ ceramic layer integral peeling in the ceramic layer/bond coating interface in a very short time during cooling stage. Under the same conditions, columnar PS-PVD 7YSZ coating has not obvious flaking after 20h, but numerous corrosion microspores occurs in the upper end of the columnar crystals.(3) After heating treat at 1250 ℃ for 20h, the PS-PVD 7YSZ coating with CMAS deposited and without CMAS deposited have no spallation phenomenon happens. However, PS-PVD 7YSZ coating with CMAS deposited has many corrosion porous in the columnar crystal area.(4) After thermal cycling 240 times, the columnar PS-PVD 7YSZ coating with CMAS deposited occurs obvious spalling at the sample edge and the center position of the coating has a lot of corrosion pits. The coating is failure when the peeling area exceeded 5%. Columnar PS-PVD 7 YSZ coating without CMAS deposited does not appear obvious peeling after thermal cycling 240 times, but transverse cracks appear in TGO/bond coating interface.(5) After heating treat 20h at 1250 ℃, PS-PVD 7YSZ coating with CMAS deposited happened obvious spalling under the dynamic environment (thermal shock process) and occurred many part corrosion microspores in the segment of columnar crystals. While the static environment (constant temperature heating processing), PS-PVD 7 YSZ coatings did not occur obvious flaking, but there are also a number of columnar crystals upper corrosion microspores.