Analysis of the Hydrogen Induced Cracking by Means of the Small Punch Test: Effect of the Specimen Geometry and the Hydrogen Pre-Charge Mode

Guillermo Álvarez Díaz,Cristina Rodríguez González,Mario López Gallego,Pablo Vinjoy Rodríguez

doi:10.3390/proceedings2231418

Abstract

This paper presents a simplified procedure to analyse the Hydrogen Induced Cracking (HIC) of structural steels by means of the Small Punch Test (SPT). Two types of notched specimens were used: one with through-thickness lateral notch and another with surface longitudinal notch. The results for conventional specimens were compared with those for hydrogen pre-charged specimens. For this purpose, two different methods to introduce hydrogen in the specimens were used: cathodic/electrochemical pre-charging and pressurized gaseous hydrogen pre-charging. The results obtained with both methods are also discussed.

Highlights

Standardized tests such as the tensile test, the fracture toughness or the slow strain rate test (SSRT) require large specimens that cannot be obtained from in-service structures without compromising their structural integrity
Two techniques were used to hydrogen pre-charge both types of notched small punch test (SPT) specimens: the pressurized gas method and the electrochemical method
Regardless of the type of notch, the precharged hydrogen is only noticeable in the last part of the load-displacement curves, whose maximum takes place at lower values of load and displacement

Summary

Introduction

Standardized tests such as the tensile test, the fracture toughness or the slow strain rate test (SSRT) require large specimens that cannot be obtained from in-service structures without compromising their structural integrity. The hydrogen induced cracking usually appears during the in-service life of structures. On this grounds, the SSRT is commonly used for analysing mechanical properties in the presence of aggressive hydrogen environments [1], a different mechanical test is required when the volume of material available for testing is limited. The tensile tests parameters that are commonly used in the mechanical characterization of materials can be estimated with the results of the SPT. For these two reasons, the SPT has been proposed to analyse the deterioration of mechanical properties due to HIC [3]

Methods

Results

Conclusion