High temperature creep study on thermally grown oxide by tensile combined with a digital image correlation method

Abstract

A thermally grown oxide (TGO) layer usually generates at the interface between the ceramic coating and the bond coating during the long-term high temperature service. TGO creep can affect the service life of thermal barrier coatings. In this paper, a dense TGO layer with a thickness of 4 μm is formed on the surface of the PtAl bond coating. The high-temperature creep behavior of the TGO layer is investigated by tensile combined with a digital image correlation method. The creep mechanism of TGO at 750 °C–950 °C is dislocation creep (stress exponent ∼4, and creep activation energy of 706–815 kJ/mol). The creep strain rate of TGO at 750 °C–950 °C is in the range of 4.7 × 10−6 s−1–4.7 × 10−4 s−1. The failure behavior of the TGO layer is significantly affected by temperature and applied stress. As the temperature and stress increase, the surface vertical cracks initiate at the TGO surface and propagate to the interface of TGO/PtAl bond coating, leading to the delamination and cracking of TGO layer.

Keywords

• Thermally grown oxide
• High temperature creep
• Stress exponent
• Creep activation energy
• Failure analysis