Damage resistance of a thermal barrier coated superalloy used in aero turbine blade under accelerated creep condition

• This paper highlights the hot tensile and accelerated creep properties of a thermal barrier coated (TBC) AE 437A alloy used as a candidate blade material in aero engines. Acoustic emission technique has been utilised to characterise the ductile-brittle transition temperature of the bond coat. Results revealed that the DBTT (ductile to brittle transition temperature) of this bond coat is around 923 K, which is in close proximity to the value reported for NiCoCrAlY type of bond coat. Finite element technique used for analysing the equivalent stresses in the bond coat well within the elastic limit, revealed highest order of equivalent stress at 1073 K as the bond coat is ductile above 923 K. The lifetime of the TBC coated superai loy was superior to that of the bare substrate and that oxidation is likely the cause of the reduced life of the bare substrate as compared to the coated substrate while stress rupture or accelerated creep experiments are carried out in an oxidizing environment.. Delamination of the bond coat and that of the TBC at high stresses during accelerated creep was evident. During accelerated creep, the mode of fracture in the substrate at very high stresses was transgranular whereas that at low stresses was intergranular.

Keyword

Creep

Finite element

Fractography

Intergranular

Spallation

Substrate

Tensile

Thermal barrier coating

Trans-granular

A-thermal

Acoustic emission techniques

Aero-engine

Bond coats

Close proximity

Coated substrates

Coated superalloys

Creep conditions

Creep properties

Damage resistance

Ductile-brittle transition temperature

Ductile-to-brittle transition temperature

Elastic limit

Equivalent stress

Finite element techniques

High stress

Hot tensile

Low stress

Mode of fracture

NiCoCrAlY

Oxidizing environments

Stress rupture

Transgranular

Turbine blade

Acoustic emissions

Finite element method

Fracture mechanics

Inorganic coatings

Spalling

Substrates

Superconducting transition temperature

Textures

Thermoelectricity

Turbomachine blades

Thermal barrier coatings

Publication and Content Type

ref (subject category)

art (subject category)