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ENVIRONMENT SENSITIVE CRACKING OF TITANIUM ALLOYS IN OFFSHORE STRUCTURES

Objective

The main purpose of this project is the study of the behaviour of titanium grades 2, 5 and 12 in hydrogen uptake environments and the role of hydrogen and hybrides in the mechanism of cracking.
Titanium grade 12 alloy was found to have the highest hydrogen absorption rate and hybrid precipitation among the specimens tested. Ti grades 5 and 12 suffered loss of ductility when slowly strained in a hydrogen-producing medium. Ti grade 5 showed a slight sensitivity in crack growth rate under testing. Beta phase content and distribution strongly influences the embrittlement of Ti alloys.
THE EFFECT OF DIFFERENT HYDROGEN CONTENTS, CORROSION FATIGUE VARIABLES, HYDROGEN ABSORPTION RATES IN CREVICES UNDER ABRASIVE CONDITIONS AND CHANGES IN MICROSTRUCTURE PRODUCED BY WELDING ON TITANIUM GRADES 2,2 AND 12 WILL BE CONSIDERED IN THIS PROJECT. THIS DATA, TOGETHER WITH THE METALLOGRAPHIC, FRACTOGRAPHIC AND CRACK TIP STUDIES, WILL ALLOW TO ESTABLISH A MODEL OF THE MECHANISM OF CRACKING AND LIFE PREDICTION. THE DEVELOPMENT OF A RELIABLE ENVIRONMENT SENSITIVE CRACKING MODEL COULD BE VERY VALUABLE IN PREDICTING THE LONG PERFORMANCE OF TITANIUM ALLOYS IN THE OFFSHORE STRUCTURES.

TITANIUM IS AN EXCELLENT MATERIAL IN SEA WATER ENVIRONMENTS DUE TO ITS VERY GOOD CORROSION RESISTANCE. THE MATERIAL HAS ALSO HIGH RESISTANCE IN HIGH TEMPERATURE HYDROCARBON ENVIRONMENTS. AN INCREASE OF THE USE OF TITANIUM FOR OFFSHORE PRODUCTION EQUIPMENT, WITH PARTICULAR EMPHASIS ON SUB-SEA SYSTEMS, IS FORESEEN.

THE DEVELOPMENT OF A RELIABLE ENVIRONMENT SENSITIVE CRACKING MODEL COULD BE VERY VALUABLE IN PRODUCING THE LONG TERM PERFORMANCE OF TI ALLOYS IN THE OFFSHORE STRUCTURES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

INASMET
Address
Camino Portuetxe 12
20009 San Sebastian
Spain

Participants (3)

IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE
United Kingdom
Address
South Kensington Campus
London
INSTITUT FOR ENERGY TECHNOLOGY (KJELLERS)
Norway
TECHNICAL RESEARCH CENTRE
Address

Espoo