Deposition and CMAS Corrosion Mechanism of 7YSZ Thermal Barrier Coatings Prepared by Plasma Spray-Physical Vapor Deposition

doi:10.15541/jim20140397

Abstract

Abstract:

Using agglomerated and sintered ZrO₂-7wt%Y₂O₃(7YSZ) powders as raw materials, columnar thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD) at substrate temperature of 850 ℃. The microstructures of columnar coating were analyzed by field emission-scanning electron microscope (FE-SEM). Based on the theory of atoms together, the formation and growth process of 7YSZ nucleus were investigated and the deposition mechanism of columnar coating was also analyzed. Besides, under the temperature of 1200 ℃, the CMAS (CaO-MgO-Al₂O₃-SiO₂) corrosion of columnar 7YSZ coating was examined and its failure mechanism was also discussed. During the deposition process of columnar 7YSZ coating, the 7YSZ gas molecules were firstly absorbed on substrate, then through diffusion and migration, the critical nucleus formed rapidly. Besides, the critical nucleus further grew up forming crystal island by absorbing other molecules. Then after following four steps of island formation, union formation, channel formation and continuation, the columnar coating formed eventually. When above melting temperature, the CMAS could penetrate into porous columnar coating by capillary force and react with the 7YSZ coating. Finally, the cracks appeared in the coating due to thermochemical and thermomechanical interaction.

Key words: plasma spray-physical vapor deposition, deposition mechanism, CMAS corrosion, corrosion mechanism

CLC Number:

TQ174

ZHANG Xiao-Feng, ZHOU Ke-Song, SONG Jin-Bing, DENG Chun-Ming, NIU Shao-Peng, DENG Zi-Qian. Deposition and CMAS Corrosion Mechanism of 7YSZ Thermal Barrier Coatings Prepared by Plasma Spray-Physical Vapor Deposition[J]. Journal of Inorganic Materials, 2015, 30(3): 287-293.

Figures/Tables 8

Table 1 Coating parameters of 7YSZ thermal barrier prepared by PS-PVD

Materials	Power /kW	Ar /slpm	N₂ /slpm	Feed rate /(g?min^-1)	Carrier Gas Ar /nlpm	Stand-off distance/mm	Pre-heating temperature/℃	Chamber pressure /Pa
7YSZ	127	35	60	2×9	16	950	850	150

Table 2 Compositions of vermiculite obtained by XRF

Oxides	CaO	MgO	Al₂O₃	SiO₂	Rest (Fe₂O₃, Na₂O, K₂O, etc)
Weight /wt%	2	21	17	42	18

Fig. 1 DSC-TG analysis of Vermiculite

Fig. 2 Microstructures of 7YSZ coating prepared by PS-PVD (a) Cross-section view; (b) Surface; (c) Bottom view of cross-section area (1) and (d) Top view of cross-section area (2) in (a)

Fig. 3 Physical process of nucleus formation and grown (a) Molecule diffusion; (b) Molecule group; (c) Critical nucleus; (d) Stable nucleus; (e) Island phase; (f) Union phase; (g) Channel phase

Fig. 4 Schematic diagram of microstructure model[23-24]

Fig. 5 Corrosion of columnar 7YSZ coating (a) Before corrosion; (b) After corrosion at 1200℃ for 24 h; (c) Enlarged coating tip in Fig. b, and (d) EDS spectra of Si in Fig. b

Fig. 6 Schematic diagram of CMAS corrosion of 7YSZ coating (a) Crack delamination; (b) Mechanism of crack propagation

References 29

[1]	FENG QIANG, TONG JINYAN, ZHENG YUNRONG, et al.Service induced degradation and rejuvenation of gas turbine blades.Materials China, 2012, 31(12): 21-34.
[2]	ZHENG LEI, GUO HONGBO, PENG HUI, et al.New generation thermal barrier coatings for ultrahigh temperature applications.Journal Aeronautical Materials, 2012, 32(6): 14-24.
[3]	HUANG XU, LI ZHENXI, HUANG HAO.et al.Recent development of new high-temperature titanium alloys for high thrust-weight ratio aero-engines.Materials China, 2011, 30(6): 21-27.
[4]	GUO HONG-BO, GONG SHENG-KAI, XU HUI-BING.Progress in thermal barrier coatings for advanced aero-engines.Materials China, 2009, 28(9/10): 18-27.
[5]	STRANGEMAN T, RAYBOULD D, JAMEEL A, et al.Damage mechanisms, life prediction, and development of EB-PVD thermal barrier coatings for turbine airfoils.Surf. Coat. Technol., 2007, 202(4-7): 658-664.
[6]	GUO HONG-BO, PENG LI-QUAN, GONG SHENG-KAI, et al.Progress in EB-PVD thermal barrier coatings.Thermal Spray Technol., 2009, 1(2): 7-14.
[7]	DORIER J L, GINDRAT M, HOLLENSTEIN C, et al.Plasma Jet Properties in a New Spraying Process at Low Pressure for Large Area Thin Film Deposition. Thermal Spray Conf., Singapore, 2001, 5: 759-64.
[8]	NIESSEN K V, GINDRAT M, REFLE A.Vapor phase deposition using plasma spray-PVD.Journal Thermal Spray Technol., 2010, 19(1/2): 502-509.
[9]	HOSPACH A, MAUER G, VABEN R, et al.Columnar-structured thermal barrier coatings (TBCs) by thin film low-pressure plasma spraying (LPPS-TF).Journal Thermal Spray Technol., 2010, 20(1/2): 116-120.
[10]	REFKE A, GINDRAT M, VON K.LPPS Thin Film: A Hybrid Coating Technology Between Thermal Spray and PVD For Functional Thin Coatings and Large Area Applications. Proceedings of the International Thermal Spray Conf., Beijing, 2007, 1: 705-710.
[11]	HALL A, DAI J, XIAO T.Low Pressure Plasma Spray-thin Film at San-dia National Laboratories. Proceedings of the International Spray, Las Vegas, 2009, 5: 725-728.
[12]	HARDER B.PS-PVD processing varies coating architecture with processing parameter.Advanced Material & Processes, 2011, 51: 9-11.
[13]	SHINOZAWA A, EGUCHI K, KAMBARA M, et al.Feather- like structured YSZ coatings at fast rates by plasma spray physical vapor deposition.Journal Thermal Spray Technol., 2010, 19(1-2): 190-197.
[14]	MAUER G, VABEN R.Plasma sprayed-PVD: plasma characterristic and impact on coating properties.Journal Physicals: conference series, 2012, 406: 012005-012017.
[15]	HUA JIAJIE, ZHANG LIPENG, LIU ZIWEI, et al.Progress of research on the failure mechanism of thermal barrier coatings.Journal Inorganic Materials, 2012, 27(7): 680-686.
[16]	DREXLER J M, ORTIZ A L, PADTURE N P.Composition effect of thermal barrier coating ceramic on their interaction with molten Ca-Mg-Al-Silicate (CMAS) glass.Acta Materialia, 2012, 60(15): 5437-5447.
[17]	DREXLER J M, GLEDHILL A D, SHINODA K, et al.Jet engine coatings for resisting volcanic ash damage.Advanced Materials, 2011, 23(21): 2419-2424.
[18]	WU J, GUO H B, GAO Y Z, et al.Microstructure and thermo- physical properties of yttria-stabilized zirconia coatings with CMAS deposits.J. Euro. Ceram. Soc., 2011, 31(10): 1881-1888.
[19]	杨邦朝, 王文生, 薄膜物理与技术. 成都: 电子科技大学出版社, 1993: 144-165.
[20]	MAUER G, HOSPACH A, VABEN R, Process development and coating characteristics of plasma spray-PVD. Surf. Coat. Technol., 207, 220: 219-224.
[21]	MAUER G, JARLIGO M O, REZANKA S, et al. Novel opportunities for thermal spray by PS-PVD.Surf. Coat. Technol., DOI: 10.1016/j. surfcoat. 2014.06.002.
[22]	唐伟忠. 薄膜材料制备原理、技术及应用. 2003, 北京: 冶金工业出版社, 2003: 162-222.
[23]	THORNTON J A.Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings.J. Vacuum Sci. Technol., 1974, 11(4): 666-670.
[24]	MAUER G, HOSPACH A, ZOTOV N, VABEN R.Process conditions and microstructures of ceramic coatings by gas phase deposition based on plasma spraying.Journal Thermal Spray Technol., 2013, 22(2/3): 83-89.
[25]	MERCER C, FAULHABER S, EVANS A G, et al.R. A delamination mechanism for thermal barrier coatings subject to calcium-magnesium-alumino-silicate (CMAS) infiltration.Acta Materialia, 2005, 53(4): 1029-1039.
[26]	HE QING, LIU XINJI, LIU BO, et al.Influence of CMAS infiltration on microstructure of plasma-sprayed YSZ thermal barrier coating.China Surface Engineering, 2012, 25(4): 42-47.
[27]	CHEN X.Calcium-Magnesium-Alumina-Silicate (CMAS) delamination mechanisms in EB-PVD thermal barrier coatings.Surf. Coat. Technol., 2006, 200(11): 3418-3427.
[28]	KRAMER S, YANG J, LEVI C G, et al.C A. Thermochem.ical interaction of thermal barrier coatings with molten CaO-MgO- Al2O3-SiO2.J. Am. Ceram. Soc., 2006, 89(10): 3167-3175.
[29]	PENG H, WANG L, GUO H B, et al.Degradation of EB-PVD thermal barrier coatings caused by CMAS deposits.Progress in Natural Science: Materials International, 2012, 22(5): 461-467.