Experimental and chemo-mechanical analysis of hot corrosion influence on creep properties of DD6 single crystal superalloy in molten NaCl salt

• Published in: Engineering fracture mechanics 2022-02, Vol.260, p.108194, Article 108194
• Main Authors: Liu, H., Wang, X.M., Liu, P.Y., Zhao, Z.N., Yang, W.Z., Li, L.
• Format: Article
• Language: English
• Subjects: Chemo-mechanical analysis; Chromium; Corrosion; Corrosion tests; Crack propagation; Creep; Creep tests; Dimpling; Failure mechanisms; Fracture surfaces; Hot corrosion; Marine environment; Mechanical analysis; Mechanical properties; Nickel base alloys; Nickel-based single crystal superalloys; Single crystals; Superalloys; Tearing; Tungsten
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2021.108194

•The effect of hot corrosion on the creep properties of Nickel-based single crystal superalloy is assessed in order to reflect the real damage mechanism of turbine blade serving in marine environment.•The fracture mechanism of Nickel-based single crystal superalloy is greatly changed under the effect of molten NaCl.•The existence of molten NaCl plays a vital role on the distribution of metal elements.•A chemo-mechanical coupling model is used to assist the understanding of the failure mechanism of the salt-coated specimen. The creep tests of specimens coated with NaCl salt were carried out to investigate the influence of hot corrosion on the creep properties of DD6 under 980 °C and 275 MPa. Bared specimens were also studied to make comparison. Creep lives of the salt-coated specimens are much lower than those of the bared specimens. Metallographic analysis of the fracture surface shows that creep-rupture of the salt-coated specimens is caused by a main tearing ridge rather than the connection of dimples in the bared specimens. Directional diffusion of metallic elements, i.e. Cr, Ta, and W, happens in hot corrosion-creep test due to the chemical gradient. The location of Al-rich region in the salt-coated specimen is found along the path of crack propagation. The microstructure evolution of γ/γ′ is different between the salt-coated specimens and the bared specimens. A chemo-mechanical coupling model was used to assist the understanding of the failure mechanism of the salt-coated specimen. The simulation results prove that the anodic concentration is a basic factor for the appearance of the main tearing ridge and Al-rich region in the salt-coated specimen. These findings can be helpful to understand the mechanical properties of Nickel-based single crystal superalloys in marine environment.