摘要
Abstract
This study aims to enhance the resistance of columnar-like thermal barrier coatings(TBCs)fabricated by plasma physical vapor deposition(PS-PVD)against Calcium-Magnesium-Alumino-Silicate(CMAS)corrosion,and to elucidate the influence of surface microstructural modification on corrosion resistance and thermal shock lifetime.Yttria-stabilized zirconia(8YSZ)and Yb-modified gadolinium zirconate((Gd0.9Yb0.1)2Zr2O7,GYbZ)are selected as the ceramic coating and protective layer materials in this work.Owing to the high-power and low-pressure characteristics of the PS-PVD process,controlled adjustment of processing parameters allows mixed-phase(solid-liquid-vapor)deposition,enabling microstructural design and optimization of the coating to meet diverse functional and performance requirements.A PS-PVD process dominated by liquid-phase deposition is developed through optimization of spraying parameters,enabling the formation of a dense protective layer.A tri-layered 8YSZ/GYbZ/dense GYbZ TBC system is continuously deposited on the substrate surface.The thermal shock behavior and CMAS corrosion resistance of the coatings are systematically evaluated,and their microstructure,phase composition,and elemental distribution are characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).Results indicate that the protective layer exhibits a predominantly lamellar structure containing a small number of partially molten particles,in sharp contrast to the columnar structures of the underlying 8YSZ and GYbZ layers,leading to a significant improvement in coating density.The protective layer is bonded to the ceramic surface without any detectable interfacial cracks or delamination.In addition,it effectively covers the intercolumnar gaps and seals the open pores on the surface of the ceramic layer,thereby improving surface integrity.Furthermore,its incorporation does not markedly reduce the thermal shock resistance,with the coating sustaining up to 110 water-quenching cycles.For the samples without a protective layer,coating spallation primarily occurs at the thermally grown oxide(TGO)and the ceramic layer leads to large-area delamination of the ceramic coating.In contrast,for the samples with a protective layer,spallation mainly takes place at the interface between the protective layer and the ceramic layer.Owing to the relatively low strain tolerance of the protective layer,significant interfacial stresses are generated initiating crack formation.However,lateral cracks at the interface effectively impede the downward propagation of surface vertical cracks,thereby preventing large-scale delamination of the ceramic layer.Three types of region-specific CMAS powders are synthesized according to the compositions of deposits extracted from the surfaces of engine blades operating in different regions,in order to assess the coating's resistance to CMAS corrosion under various environmental contaminant conditions.CMAS corrosion tests conducted at 1 250℃for 2 h using compositions representative of different geographical sources reveal that the protective layer effectively suppresses CMAS infiltration.This improvement is attributed to two synergistic mechanisms:(i)the dense microstructure providing a physical barrier to melt penetration,and(ii)the in-situ formation of high-melting-point apatite and spinel phases during the CMAS-coating interaction,which increase melt viscosity and further retard infiltration.The average CMAS penetration depth in samples with the protective layer is only 29.8%of that in unprotected coatings.Additionally,the dense protective layer effectively seals open pores,including intercolumnar gaps,feather-like dendritic voids,and microcracks,thereby mitigating CMAS infiltration driven by capillary forces and significantly enhancing the coating's overall corrosion resistance.关键词
PS-PVD/热障涂层/环境沉积物/腐蚀行为/致密涂层Key words
PS-PVD/thermal barrier coatings/CMAS/corrosion behavior/dense coating分类
矿业与冶金
