This paper describes a through‐process modelling on a microstructural level of the production of a coated turbine blade, including its in‐service properties and degradation, accompanied by the actual production and testing of a CMSX‐4 single crystal turbine blade dummy. The following steps are dealt with by modelling and experiment: solidification of the blade alloy during casting, microstructural changes during homogenization and aging heat treatments, chemical vapour deposition of an Al2O3 diffusion barrier coating, physical vapour deposition (sputtering) of a (Ni,Co)CrAlY bond coat, atmospheric plasma spraying of an Y2O3 stabilized ZrO2 thermal barrier coating and microstructural changes and development of critical stresses at in‐service conditions. This work forms a part of the Collaborative Research Centre 370 (SFB 370) “Integrative materials modelling”.
Single crystalline Al 2 O 3 fibres (sapphire), coated with the NiAl alloy IP75 by physical vapour deposition (PVD), were assembled to fabricate composites by means of diffusion bonding. The microstructure and chemistry of both as-coated fibre and as-diffusion bonded composites were investigated by electron microscopy and microanalysis. The interface shear stress for complete debonding was measured by fibre push-out tests at room temperature, and the composite tensile strength was measured at 900 C and 1100 C. An amorphous layer with a thickness of about 400 nm formed between the fibre and the matrix during the PVD process and was maintained during diffusion bonding. A Laves phase precipitated along NiAl grain boundaries in the IP75 matrix. This caused a lower tensile strength of the IP75/Al 2 O 3 composite at high temperatures compared to as-cast monolithic IP75 and rendered the composite useless for structural applications.
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