The influence of microstructure on the ductile to brittle transition and fracture behaviour of HVOF NiCoCrAlY coatings determined via small punch tensile testing

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:754

Article

Jackson, G. A.¹  Sun, W.¹  McCartney, D. G.¹ 

[1] Univ Nottingham, Fac Engn, Univ Pk, Nottingham NG7 2RD, England

关键词: Small punch tensile testing;    NiCoCrAlY;    MCrAlY;    HVOF;    DBTT;    Fracture;    Mechanical properties;   

DOI  :  10.1016/j.msea.2019.03.108

来源: Elsevier

【 摘 要 】

The development of new thermal barrier coatings (TBC's) capable of increasing the efficiency of gas-powered turbines requires an understanding of how the tensile behaviour and ductile to brittle transition temperature (DBTT) of MCrAlY bond coats are influenced by the coating microstructure. In this study, small punch tensile (SPT) tests were conducted on two high velocity oxy-fuel (HVOF) NiCoCrAlY coatings. Both coatings, referred to as BC1 and BC2, comprised a BCC beta-NiAl matrix with FCC gamma-Ni and TCP sigma-Cr2Co secondary phases. Coating BC2 also contained FCC gamma'-Ni3Al. Small punch tensile (SPT) tests were conducted on the coatings between RT and 750 degrees C. The DBTT's of coatings BC1 and BC2 were found to be 600-700 degrees C and 650-750 degrees C respectively. Lower phase fractions of gamma-Ni were shown to increase the DBTT. The main mode of crack propagation in both coatings was intergranular fracture along the grain boundaries of differing phases. Schematic models were used to demonstrate the change in tensile behaviour across the DBTT and explain the influence of the coating micro-structure on the fracture behaviour of both coatings.

【 授权许可】

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