Damage Mechanisms in Creep Strength Enhanced Ferritic (CSEF) Steels (T91 and T23)

The use of Creep Strength Enhanced Ferritic Steels (CSEFs), such as P91 and T23, is becoming more prevalent as boilers are used in cycling service and at higher steam temperatures.  The service experience of these materials has presented some unpleasant surprises.  There are several damage mechanisms that are commonly found in these types of materials that will be discussed.  These mechanisms include both anodic and cathodic stress corrosion cracking (SCC), brittle fracture from processing, and hydrogen-induced cracking (HIC).  Examples of each type of failure are included.

Keywords: CSEF steels, tube damage mechanisms, SCC, HIC, brittle fracture, P91, T23, creep