A Two Day Conference on Fabrication and Use of P91 Steel: International Industry & Plant Experience was hosted in Newcastle, Australia on 11th – 12th October 2017.
AMCO Integrity Pty Ltd presented a paper on “Advance materials integrity assessment analysis”, in Fabrication and Use of P9 Steel organized by ETD Consulting in Newcastle NSW Australia.
The relatively new 9Cr martensitic steels P91 and P92 have helped to increase power plant temperatures, pressures and efficiency for the new generation of plants. They are also used as replacement components in older power plants where this has helped to increase plant flexibility and reduced component fabrication, replacement and related costs. However, these steels can only achieve their design strength if they are heat treated strictly to their specified heat treatment temperatures. As their high strength strictly depends on achieving ideal martensitic microstructure slight deviations from the specified temperatures, during manufacture, fabrication and welding can lead to disastrous consequences. Unfortunately, plant experience has shown that today P91 steel components are found in many power plants with various ‘aberrant’ or abnormal microstructures resulting in premature failures worldwide. Without long term creep strength data for these aberrant microstructures it is difficult to predict their safe operating life with any degree of certainty. The other factors that need special consideration are component inspection, monitoring and integrity/ life assessment. The last factor can be particularly problematic as micron size cavitation observed by traditional NDE tools in these steels, which has been successfully used in low alloy steels for creep life exhaustion studies, appears only late in life and therefore new concepts/ technologies/ techniques are required to enable plant operators to inspect early stage smaller size creep cavitation (nano or a few micron size), and predict damage/ failure and make ‘run, repair or replace’ decisions.
Luckily a number of industry initiatives are now underway to address these issues and these will be discussed in this conference. The objective is to bring together plant manufacturers, fabricators, operators, service providers and researchers on one platform and learn from plant and research experience to date.