Hydrogen embrittlement of steels: study and prevention

Hydrogen embrittlement of steels, often referred to as FPH, is a major cause of component failure in industry. The often brutal nature of these failures, and the human and economic consequences that can result, have been the subject of numerous studies and publications since the phenomenon was first identified over a century ago.

There are many different situations that can lead to FPH phenomena:

• introduction of hydrogen into the material during production or processing (heat treatment, welding);

• use of steels in the presence of hydrogen or hydrogenated gas mixtures;

• hydrogen produced by electrolytic reactions (surface treatments, cathodic protection);

• hydrogen from corrosion reactions (aqueous environments).

Hydrogen embrittlement can manifest itself in a variety of ways, depending on a multitude of parameters:

• material (condition, composition, microstructure...) ;

• surrounding environment (gas, aqueous medium, temperature, etc.) ;

• mechanical stress conditions (static, dynamic, cyclic, etc.).

Developments in techniques and processes, the quest for higher yields, and cost reductions mean that materials can be made to work under increasingly severe conditions. Significant developments in the steels themselves, in manufacturing and processing techniques, and in the way they are used, mean that new studies are always required. Solutions to problems of hydrogen embrittlement are never definitive, and in many cases, for reasons of economic gain or safety, it is important to reconsider the effectiveness of the solution. Finally, more and more users of parts, reactors or metal structures that may be embrittled by hydrogen are looking for reliable techniques or models to predict, monitor and control the evolution of damage that may occur in service.