Experience with the use of P91 steel & development of tools for component integrity/life assessment
Martensitic steels, such as ASME P91, with higher creep strength, were introduced as thick section components in many power plants between 10 to 20 years ago. These were initially introduced used in the European and Japanese utilities but are now used regularly in both the conventional power plants and in Heat Recovery Steam Generators (HRSGs) of the Combined Cycle Gas Turbines (CCGTs) in many countries such as China, Far East, North America etc. For the HRSGs there is a requirement to produce compact size units and thus high strength steels are used to make smaller size components. Recently a number of failures have been experienced in both thick and thin section components and this has given rise to re- appraisal of this steel. Thick section components are generally known to have failed due to Type IV cracking (although a few failures have now occurred in the base metal as well). Furthermore, due to the restructuring of the electricity industry worldwide many of the existing steam plant are now required to operate in cycling mode and this requires the use of materials with high resistance to thermal fatigue. Here high strength P91 is assumed to offer an additional benefit in that the reduced section thickness increases pipework flexibility and reduces the level of through wall temperature gradients in thick section components. Because of this envisaged benefit a number of operators/owners of the existing plant have been substituting these new higher strength steels for the older materials, especially when a plant is moved from base load to cyclic operation. With regard to the thin section components, there has also been a perceived advantage of higher steam side oxidation resistance of superheater tubes made from high Cr martensitic steels. Here again the actual plant experience has not been so favorable. This paper discusses the thick section component issues and compares the envisaged benefits with the actual plant experience and more recent R & D findings. In view of these incidents of cracking and failures it is important to develop life assessment tools for components made from P91 steel. ETD has been working on this through a multi-client project and this aspect will be discussed in this paper.
Creep Fatigue Creep-fatigue interaction P91 Power plant Integrity/life assessment
Ahmed Shibli David Robertson
European Technology Development, Surrey, UK
国际会议
国际断裂力学2007年会(Fracture Mechanics and Applications 2007)
长沙
英文
373-382
2007-11-01（万方平台首次上网日期，不代表论文的发表时间）