Correlation between microstructure and nanomechanical properties of 9Cr-1Mo ferritic martensitic steel through instrumented indentation technique

Instrumented indentation technique (IIT) has been used to probe the phase-specific nanomechanical properties of heat treated 9Cr 1Mo ferritic martensitic (P9) steel. P9 steel was subjected to austenitization treatment, followed by water quenching, normalizing, furnace cooling, and subsequently tempering. Quantitative TEM analysis showed systematic changes in microstructure with variation in cooling rate in aforementioned heat treatments. Instrumented indentation tests were carried out at room temperature with a spherical indenter for evaluating hardness and elastic modulus. The yield strength of the steel from the load-displacement curves of cyclic indentation tests has been derived using neural networking method and yield parameter calculations. The properties derived from IIT using these methods were also validated with tensile test results. This work aims at correlating the local mechanical response measured by IIT with microstructural changes due to different heat treatments, which would be useful to extract mechanical properties of materials with heterogeneous microstructure.