Effect of Microstructure of Pipeline Steels on Ductility and Fatigue Properties in High Pressure Hydrogen Atmosphere

Main Objective

A number of studies have been conducted in the past to understand the effect of the steel composition and microstructure on the tendency to lose ductility through hydrogen-induced embrittlement. Although some general rules have been developed to relate the properties of steels with the tendency for hydrogen embrittlement, much needs to be learned on the effect of many alloying elements on the hydrogen embrittlement in steels. The main objective is to conduct fatigue and fracture-toughness property test. Fatigue damage is typically divided into three stages: crack initiation, crack propagation and final failure. These three stages are important in determining the fatigue life of structural components. Fatigue-crack-growth-rate properties are of vital importance for the structural-reliability assessment, when a structural component is subjected to cyclic loading. Fatigue-crack propagation-rate results can be used to predict the crack-growth life of a component.

Public Abstract

Comprehensive knowledge of mechanical properties of pipeline steels in high-pressure hydrogen is essential for the structural integrity of a pressurized hydrogen transport system. This project focuses on obtaining much needed data on fracture toughness and fatigue life for base steels. For testing of base steels, compact tension specimens will be employed in cost-effective testing techniques developed in previous federal-funded programs will be further refined and applied to investigate the effects of pressure and temperature on the degradation of base metal fracture toughness in high-pressure hydrogen.
A novel cost-effective low-frequency fatigue test apparatus will be developed to determine the base metal fatigue life under realistic in-service cyclic loading frequencies of hydrogen pipelines. These property data will be critical to support industry consensus standards for hydrogen transport via pipeline, and to support the design and maintenance operation by pipeline operators.