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In aero-turbine engines,thermal barrier coatings(TBCs) must be capable to withstand harsh environments,such as high-temperature oxidation and hot-corrosion.Recently,a new failure mode of TBCs caused by calcium-magnesium-alumina-silicate(CMAS) glass has attracted increasing attention.In this paper,yttria stabilized zirconia(YSZ) TBCs produced by electron beam physical vapor deposition(EB-PVD) were exposed to CMAS deposits at 1250℃.The microstructure evolution and failure mechanism of the coatings were investigated.It has been shown that CMAS glass penetrated into the YSZ ceramic layer along the inter-columnar gaps and interacted with YSZ.As a result,an interaction zone of about 20μm thickness,which was the mixture of CMAS and YSZ with equiaxial structure,was formed in the YSZ surface layer after 4h heat-treatment at 1250℃.Meanwhile,yttria in YSZ layer as a stabilizer was dissolved in CMAS glass and caused accelerated monoclinic phase transformation.After 8h heat-treatment,degradation of YSZ TBC occurred by delamination cracking of YSZ layer,which is quite different from the traditional failure caused by interfacial cracking at the YSZ/metallic bond coat.Physical models have been built to describe the failure mechanism of EB-PVD TBCs attacked by CMAS deposits.
In aero-turbine engines, thermal barrier coatings (TBCs) must be capable of withstand harsh environments, such as high-temperature oxidation and hot-corrosion. Rescently, a new failure mode of TBCs caused by calcium-magnesium-alumina- ) TBCs produced by electron beam physical vapor deposition (EB-PVD) were exposed to CMAS deposits at 1250 ° C. The microstructure evolution and failure mechanism of the coatings were investigated .It has been shown that CMAS glass penetrated into the YSZ ceramic layer along the inter-columnar gaps and interacted with YSZ. As a result, an interaction zone of about 20 μm thickness, which was the mixture of CMAS and YSZ with equiaxial structure, was formed in the YSZ surface layer after 4h heat-treatment at 1250 ° C. Meanwhile, yttria in YSZ layer as a stabilizer was dissolved in CMAS glass and caused accelerated monoclinic phase transformation. After 8h heat-treatment, degradati on of YSZ TBC occurred by delamination cracking of YSZ layer, which is quite different from the traditional failure caused by interfacial cracking at the YSZ / metallic bond coat. Physically models have been built to describe the failure mechanism of EB-PVD TBCs attacked by CMAS deposits.