The creep strength of aberrant grade 91 steel

The high-temperature steel grade 91 is intended to operate in service with a fully martensitic microstructure, achieved by a well-defined heat treatment. Unfortunately, lack of control, either during the initial material manufacturing or later during post-weld heat treatment, can lead to components entering service in a substandard condition. In the worst cases, this can be a fully ferritic microstructure with a complete absence of martensite....