Phases Micromechanical Properties of Ni-base Superalloy Measured by Nanoindentation
This investigation describes the changes in the phase’s micromechanical properties as a result of alloying elements moving at interdiffusion. The induction of the interdiffusion between different phases of a Ni-based single crystal superalloy still is a challenging issue in this field of the materials science. For this we used novel technique - hard cyclic viscoplastic deformation at room temperature. The chemical compositions of the phases were determined by the cumulative bulk deformation. For detailed knowledge of this material behavior during life time the micromechanical properties of phases were investigated by nanoindentation and the results were analyzed by scanning electron microscope and the corresponding chemical content was investigated by X-ray microanalysis.It was established, that the calculated results values depend on indentation load stepwise increase from 5 to 10 and 20 mN, respectively. The hardness, contact compliance and elastic recovery parameters decrease, while indentation modulus, elastic- and plastic parts of indentation work increase with load increase. In initial material the hardness, indentation modulus and elastic recovery parameter for the γ/γ’-microstructure with coarse intermetallic γ’-precipitates were lower with compared to microstructure with fine γ’-precipitations. As a result of interdiffusion the chemical content was changed and these parameters for the coarse γ/γ’-microstructure increased as the γ’-Ni3Al content was increased, while these values in the γ-γ’-eutectic and Nb/Ta-rich phases decreased as the niobium and rhenium contents decreased, respectively. By this the lakes of γ-γ’-eutectic phase have maximal plastic part of indentation work with compare to other phases of superalloy. The cumulative bulk deformation increases lead to decrease of dendrites dimensions.
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