In-situ Crack Tip Stress Measurement at High Temperature in IN-617 Using Combined Nano-Indentation and Nano-Mechanical Raman Spectroscopy

摘要

In this work, the in-situ measurement of crack tip stresses in Inconel 617 at high temperature is presented. The temperature during loading in the current work was varied in the range from room temperature to 1073 K (800 °C). Three-point bending tests for in-situ notch tip stress measurements with increasing load were performed. A Combined Nano indentation and Nano mechanical Raman spectroscopy (NMRS) methods are used to measure notch tip plasticity induced stress distribution. Optical microscopy and SEM imaging is used to analyze the effect of surface finish and oxidation on the Nano indentation measurements. An in-situ Nano mechanical Raman spectroscopy is used to obtain the stress distribution at the notch tip during three point bending. The size resolution of measurements of notch-tip stresses was in the range of few microns. Temperature dependent (up to 1073 K) material properties were studied in terms of hardness and elastic modulus variation as a function of temperature. Microstructure dependent local mechanical properties were obtained using Nano indentation and is used in the finite element simulation. A finite element method based formulation to predict microstructure and temperature dependent crack tip stresses is presented and validated using the experimental stress distribution obtained from NMRS.