A creep testing programme was conducted at 923 K to identify the properties for new and repaired welds fabricated in a 9CrMoNbV grade P91 steel using a 9CrMoNbV weld metal. The material data obtained were assessed and used to determine the material creep and damage constitutive equations for the parent material (PM), weld metal (WM) and heat-affected zone (HAZ) materials in the P91 welds. Steady state creep and continuum damage finite element analyses were performed to assess the failure behaviour of the circumferential welds in the pipes, under two internal pressures and a range of end load levels. A full post-weld heat treatment is assumed to have been carried out, and any effects of welding-induced residual stresses were neglected. The results obtained have illustrated the main features of life reduction of a P91 pipe owing to the presence of welds, an additional life reduction due to repair and the more limited life reduction due to geometry difference, for the particular set of material properties used.
ColemanM. C.MillerD. A.Inspection, assessment and repair strategies for type IV cracking in power plant components. AWS/EPRI Conference onMaintenance and Repair Welding in Power Plants V, Florida, 1994, pp. 5–15.
2.
WilliamsJ. A.Methodology for high temperature failure analysis. In Proceedings of European Symposium onBehaviour of Joints in High Temperature Materials (Eds GoochT. G.HurstR.MerzM.), 1982 (Petten, the Netherlands).
3.
BrettS. J.Identification of weak thick section modified 9Cr forgings in service. 3rd EPRI Conference onAdvances in Materials Technology for Fossil Power Plants, Swansea, UK, 2001.
4.
BrettS. J.AllenD. J.PaceyJ.Failure of a modified 9Cr header endplate In Case Histories on Integrity and Failures in Industry (Eds BicegoV.NittaA.PriceJ. W. H.ViswanathanR.), 1999, pp. 837–884.
5.
AllenD. J.BrettS. J.Premature failure of a P91 header endcap weld: Minimising the risks of additional failuresCase Histories on Integrity and Failures in Industry (Eds BicegoV.NittaA.PriceJ. W. H.ViswanathanR.), 1999, pp. 133–143.
6.
ColemanM. C.The structure of weldments and relevance to high temperature failure. 5th Bolton Landing Conference on Weldments in Physical Metallurgy and Failure Phenomena, 1979 (General Electric, USA).
7.
Technische Regeln für Dampfkessel. DDA, TRD 508, Cologne, Germany.
8.
SunW.HydeT. H.BeckerA. A.WilliamsJ. A.A study of weld repairs in a CrMoV service-exposed pipe weld. In Proceedings of 9th International Conference onCreep and Fracture of Engineering Materials and Structures, Swansea, April 2001, pp. 613–622.
9.
BuddenP. J.Analysis of modified 9Cr weldment creep behaviour using a four-material model. Nuclear Electric report TD/SE/REP/0061/92, 1992.
10.
EggelerG.RamtekeA.ColemanM.ChewB.PeterG.BurbliesA.HaldJ.JeffereyC.RantalaJ.de WitteM.MohrmannR.Int. J. Pressure Vessels and Piping, 1994, 60, 237–257.
11.
HydeT. H.WilliamsJ. A.BeckerA. A.SunW.The influence of heat affected zone characteristics on the creep failure of P91 welds: An initial sensitivity study using steady state creep In Material Science Forum, 2003, Vols 440–441, pp. 465–472 (Trans Tech Publications, Switzerland).
12.
HydeT. H.SunW.BeckerA. A.Analysis of the impression creep test method using a rectangular indenter for determining the creep properties in weldsInt. J. Mech. Sci., 1996, 38, 1089–1102.
13.
HydeT. H.SunW.Determining high temperature properties of weld materialsJap. Soc. Mech. Engrs Int. J. Solid Mechanics and Mater. Engng, Series A, 2000, 43, 408–414.
14.
The manufacture and properties of steel 91 for the power plant and process industries. ECSC Information Day, Commission of the European Communities, 5 November 1992, VDEH, Düsseldorf, Germany.
15.
PonterA. R. S.The derivation of energy theorems for creep constitutive relationships. IUTAM Symposium onCreep of Structures, Gothenburg, Sweden, 1970, pp. 123–136 (Springer-Verlag, Berlin).
16.
HayhurstD. R.Vakili-TahamiJ. Q.ZhouJ. Q.Constitutive equations for time dependent plasticity and creep of 316 stainless steel at 550°CInt. J. Pressure Vessels and Piping, 2003, 80, 97–109.
17.
KachanovL. M.Izv. Akad. Nauk SSSR, 1958, 8, 26.
18.
HayhurstD. R.Creep rupture under multi-axial states of stressJ. Mech. Phys. Solids, 1972, 20, 381–390.
19.
HallF. R.HayhurstD. R.Continuum damage mechanics modelling of high temperature deformation and failure in a pipe weldmentProc. R. Soc. (Lond.), 1991, A443, 383–403.
20.
HayhurstD. R.DimmerP. R.MorrisonC. J.Development of continuum damage in the creep rupture of notched barsPhil. Trans. R. Soc. (Lond.), 1984, A311, 103–129.
21.
PerrinI. J.HayhurstD. R.Creep constitutive equations for 0.5Cr0.5Mo0.25V ferritic steel in the temperature range 600–675°CJ. Strain Analysis, 1996, 31, 299–314.
22.
OrrJ.BurtonD.Experience in data collection and assessment for material standards. CEC ECSC Information Day onThe Manufacture and Properties of Steel 91 for the Power Plant and Process Industries, VDEh, Düsseldorf, 1992.
23.
HydeT. H.SunW.AgyakwaP. A.ShipwayP. H.WilliamsJ. A.Anisotropic creep and fracture behaviour of a 9CrMoNbV weld metal at 650°C In Anisotropic Behaviour of Damaged Materials (Eds SkrzypekJ. J.GanczarskiA.), 2002, Ch. 9, pp. 297–316 (Springer-Verlag).
24.
HydeT. H.SunW.WilliamsJ. A.Steady-state creep reference rupture stresses for internally pressurised pipes under additional end load. In Proceedings ofCreep 7, Tsukuba, Japan, June 2001, pp. 1–6.
25.
HydeT. H.SunW.BeckerA. A.Creep crack growth in welds: A damage mechanics approach to predicting initiation and growth of circumferential cracksInt. J. Pressure Vessels and Piping, 2001, 78, 765–771.
26.
BeckerA. A.HydeT. H.SunW.AnderssonP.Benchmarks for finite element analysis of creep continuum damage mechanicsComput. Mater. Sci, 2002, 25, 34–41.
27.
HydeT. H.SunW.BeckerA. A.Assessment of the use of finite element creep steady-state stresses for predicting the creep life of welded pipes. In Proceedings of 4th International Conference onComputational Structures Technology (Ed. ToppingB. H. V.), 1998, pp. 247–251 (Civil-Comp Press, Edinburgh).
28.
EttienneC. F.HeeringsJ. H.Evaluation of the influence of welding on creep resistanceSteel Res., 1994, 65 (5), 187–196.
29.
SunW.HydeT. H.BeckerA. A.WilliamsJ. A.Comparison of the creep and damage failure prediction of the new, service-aged and repaired thick-walled circumferential CrMoV pipe welds using material properties at 640°CInt. J. Pressure Vessels and Piping, 2000, 77, 389–398.
30.
HydeT. H.WilliamsJ. A.SunW.Assessment of creep behaviour of narrow gap weldsInt. J. Pressure Vessels and Piping, 1999, 76, 515–525.
