Abstract
The durability of atmospheric plasma-sprayed thermal barrier coatings (APS TBCs) with a double-layer bond coat was evaluated via isothermal cycling tests under 1120 °C. The bond coat consisted of a porosity layer deposited on the substrate and an oxidation layer deposited on the porosity layer. Two types of double-layer bond coats with different thickness ratios of the porosity layer to the oxidation layer (type A: 1:2 and type B: 2:1, respectively) were prepared. The results show that the porosity layer was oxidation free, the oxidation layer included a fraction of well-distributed α-Al2O3. The coefficient of thermal expansion of the oxidation layer was about 11.2 × 10−6 K−1, which was rather lower than that of the porosity layer. Thus, the oxidation layer can be regards as a secondary bond coat between ceramic topcoat and traditional bond coat. The thermal cyclic lifetime of type A TBCs was about 60 cycles, which exceeded 1.2 times the durability of type B TBCs. The delamination cracks in both TBCs all propagated in the ceramic topcoat, which were all identical to those in traditional TBCs. Therefore, the design of the double-layer bond coat affected the stress level rather than the stress distribution in TBCs.
Highlights
Thermal barrier coatings (TBCs) are normally used in aircraft engines and power generation gas turbines to protect the turbine components from high-temperature erosion and to improve the efficiency of facilities [1,2,3]
The failure of atmospheric plasma-sprayed (APS) TBCs can be affected by many factors, such as thermally grown oxide (TGO) growth [1,2,4,5,6,7,8], thermal expansion mismatch [1,8,9,10], yttria-stabilized zirconia (YSZ) sintering [11,12,13,14,15], the temperature gradient across YSZ coating [16,17,18,19] and the profile of the bond coat surface [7,20,21,22,23], etc
Powder including four four layers, layers, The structure of the TBC in this case is identical to traditional APS TBCs, including while the bond coat in this case consists of two layers: a porosity porosity layer deposited on the substrate and
Summary
Thermal barrier coatings (TBCs) are normally used in aircraft engines and power generation gas turbines to protect the turbine components from high-temperature erosion and to improve the efficiency of facilities [1,2,3]. Jiang [24] designed a double-layer bond coat with different porosities: a dense layer deposited on the substrate and a porosity layer with macro voids neighboring the YSZ coating It indicated that the porosity layer seriously internally oxidizes and rapidly swells after isothermal exposure, and the thermal expansion mismatch between the topcoat and substrate alleviates much limitedly. This layer swelling accelerates the failure of the TBCs due to the enormous residual stress induced by the roughness change at the interface. The macro voids in the bond coat which closes to the ceramic topcoat deteriorates its oxidation resistance and has no positive role on the durability of TBCs in terms of alleviation of thermal expansion mismatch. The bond coats in this case included a porosity layer deposited on the substrate and an oxidation layer, with well-distributed α-Al2 O3 neighboring the YSZ coating
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
