Depth-Sensing Indentation Creep Behavior of Nanostructured Thermal Barrier Coatings from As-Synthesized t’-8YSZ Feedstocks

Abstract

Nano-indentation is a popular method to characterize the micromechanical properties of nanostructured 8YSZ coatings. However, little research has focused on the creep behavior of nano-indentation and only the elastic modulus and nanohardness have been analyzed. Herein, for the first time, the nano-indentation creep behavior of plasma-sprayed nanostructured 8YSZ coatings using as-prepared nanostructured non-transformable tetragonal (t') feedstocks was investigated. The indentation creep behavior can be well characterized by the power-law equation and the strain rate sensitivity has been calculated in light of the equation. The strain rate sensitivity was sensitive to the load and the reasons were analyzed in detail. The current results can further guide and design thermal barrier coatings from the point of indentation creep property.Mechanical properties, embodying elastic modulus, hardness, fracture toughness and bonding strength, are extremely essential to ensure coatings with functionality, reliability, and durability during service [17,[20][21][22]. In addition to tensile testing for bonding strength, nano-indentation is also required and useful for most measurements or calculation of these mechanical properties. Nano-indentation tests in references have mostly focused on the modulus of elasticity, nano-hardness, and calculation of the fracture toughness of coatings [23][24][25]. However, these references pay little attention to the creep behavior of nanostructured 8YSZ coatings. Concerning nanostructured 8YSZ thermal barrier coatings, the stress state and distribution have influences on the properties of coatings [1,6]. It has been reported that the creep property of 8YSZ coatings can determine the stress distribution [26]. Therefore, it is of great importance to study the creep property of nanostructured 8YSZ coatings.Our previous work prepared and investigated high-performance non-transformable tetragonal (t') 8YSZ feedstocks with nanostructure [27]. In this paper, we fabricated high-performance nanostructured 8YSZ coatings from t' feedstocks using the APS method. The creep behavior of nanostructured 8YSZ coatings was studied by nano-indentation for the purpose of filling in this research gap.

Mechanical Properties of Multi-Sized Porous Thermal Barrier Coatings at Micro and Nano Scales after Long-Term Service at High Temperature

“…Nano/submicron pores had a higher sensitive influence on thermal properties than that of large pores. When the porosities were certain, the interface quantities among pores and the deposited particles increased rapidly with the reduction of pore size, which relaxed the stress and improved the strain tolerance of the material furtherly [2,21]. Zhou et al [21] investigated the nanoindentation creep behavior of plasma-sprayed nanostructured 8YSZ coatings using as-prepared nanostructured non-transformable tetragonal (t') feedstocks.…”