A Perspective of the Small Punch Test Application to the Evaluation of Hydrogen Embrittlement in Steels: Effect of Punch Rate on Fracture Properties

Abstract

In this paper, different techniques to test notched Small Punch (SPT) samples for the estimation of the fracture properties in aggressive environments are studied, based on the comparison of the micromechanisms at different rates. Pre-embrittled samples subsequently tested in air at conventional rates (0.01 and 0.002 mm/s) are compared to embrittled ones tested in environment at the same rates (0.01 and 0.002 mm/s) and at a very slow rate (5E−5 mm/s); a set of samples tested in environment under static loads that produce very slow rates complete the experimental results. To close the study, numerical simulations based on obtaining a punch rate that produces an equivalent CTOD growing rate in the edge of the notch to the one at the crack tip of a C(T) specimen for a given solicitation rate is carried out. As a conclusion, is recommended to test SPT notched specimens in environment at very slow rates, of arround E−6 mm/s, when characterizing in Hydrogen Embrittlement (HE) scenarios, in order to allow the interaction material-environment to govern the process.