S. I. Rokhlin, E. Kahana, L. Wang, X. Bin, The Ohio State University, Columbus, OH; P. B. Nagy, University of Cincinnati, Cincinnati, OH; M. P. Blodgett, US Air Force Research Laboratory, Wright-Patterson AFB, OH
Nondestructive evaluation of residual stresses and of residual stress relief in service conditions has great significance for reliability of turbine engine components. It is important to achieve better fundamental understanding of relations between nondestructive signature and material properties such as hardness, plasticity, cold-work and residual stress. In this work a nanoindentation technique is explored to determine the micromechanical properties and their relation to different levels of cold work in Ni based superalloys. It is shown that cold work has some effect on elastic modulus, in particular texture induced elastic anisotropy appear at plastic deformation above 20%. Cold work has strong effect on hardness and yield stress. Significant size effect has been observed in indentation responses. Nanoindentation measurements are also performed on shot peened Ni based superalloy samples. Local mechanical properties (Young’s modulus E, yield stress ƒnand strain hardening exponent n) are determined from nanoindentation tests based on the inverse scaling functions. The nanoindentation results are compared with non contact measurements of electrical conductivity.
Summary: Nondestructive evaluation of residual stresses and of residual stress relief in service conditions has great significance for reliability of turbine engine components. It is important to achieve better fundamental understanding of relations between nondestructive signature and material properties such as hardness, plasticity, cold-work and residual stress. In this work a nanoindentation technique is explored to determine the micromechanical properties and their relation to different levels of cold work in Ni based superalloys. It is shown that cold work has some effect on elastic modulus, in particular texture induced elastic anisotropy appear at plastic deformation above 20%. Cold work has strong effect on hardness and yield stress. Significant size effect has been observed in indentation responses. Nanoindentation measurements are also performed on shot peened Ni based superalloy samples. Local mechanical properties (Young¡&brkbar;s modulus E, yield stress ƒnand strain hardening exponent n) are determined from nanoindentation tests based on the inverse scaling functions. The nanoindentation results are compared with non contact measurements of electrical conductivity.
