Analyses of nanoscale to microscale strength and crack-tip stresses using nanomechanical raman spectroscopy in IN-617

Abstract

In this research, Inconel 617, a solid solution Ni-Cr-CO-Mo superalloy, was studied in the temperature range of room temperature to 1073 K (800 °C) for temperature dependent strength and crack propagation behavior. Elastic modulus, hardness, creep exponent, creep strain rate and thermal activation volume of the different alloy 617 samples were studied through nanoindentation method. Indentation size effect (ISE) was studied in terms of hardness variation as a function of loading depth and temperature. Three-point bending tests for in-situ crack tip stress measurements were performed on the samples with an initial crack to measure crack tip plastic stresses under applied load. A relation between indentation depth and hardness was used to predict strain gradient length scale variation from 1.008 µm at room temperature and to 1.876 µm at 673 K then decreasing to 1.228 µm at 1073 K.