A multiaxial, physically based, continuum damage mechanics methodology for creep of welded 9Cr steels is presented, incorporating a multiple precipitate-type state variable, which simulates the effects of strain- and temperature-induced coarsening kinematics. Precipitate volume fraction and initial diameter for carbide and carbo-nitride precipitate types are key microstructural variables controlling time to failure in the model. The heat-affected zone material is simulated explicitly utilising measured microstructural data, allowing detailed investigation of failure mechanisms. Failure is shown to be controlled by a combination of microstructural degradation and Kachanov-type damage for the formation and growth of creep cavities. Comparisons with experimental data demonstrate the accuracy of this model for P91 material.
AbsonDJRothwellJS. Review of Type IV cracking of weldments in 9-12%Cr creep strength enhanced ferritic steels. Int Mater Rev2013; 56: 437–473.
2.
FarragherTPScullySO’DowdNPet al.Development of life assessment procedures for power plant headers operated under flexible loading scenarios. Int J Fatigue2013; 49: 50–61.
BarrettRAO’DonoghuePELeenSB. A dislocation-based model for high temperature cyclic viscoplasticity of 9–12Cr steels. Comput Mater Sci2014; 92: 286–297.
5.
Ó Murchú C, Leen SB, O’Donoghue PE, et al. A physically-based creep damage model for effects of different precipitate types. Mater Sci Eng A 2017; 682: 714–722.
6.
OrowanE. Problems of plastic gliding. Proc Phys Soc1940; 52: 9–22.
7.
PanaitCGZielińska-LipiecAKozielTet al.Evolution of dislocation density, size of subgrains and MX-type precipitates in a P91 steel during creep and during thermal ageing at 600C for more than 100,000h. Mater Sci Eng A2010; 527: 4062–4069.
8.
HaldJKorcakovaL. Precipitate stability in creep resistant ferritic steels-experimental investigations and modelling. ISIJ Int2003; 43: 420–427.
9.
TaneikeMKondoMMorimotoT. Accelerated coarsening of MX Carbonitrides in 12%Cr steels during creep deformation. ISIJ Int2001; 41: S111–S115.
10.
HättestrandMAndrénH-O. Influence of strain on precipitation reactions during creep of an advanced 9% chromium steel. Acta Mater2001; 49: 2123–2128.
LeeJSMaruyamaK. Mechanism of microstructural deterioration preceding type IV failure in weldment of Mod.9Cr-1Mo steel. Met Mater Int2015; 21: 639–645.
13.
HaldJ. Microstructure and long-term creep properties of 9–12% Cr steels. Int J Press Vessel Pip2008; 85: 30–37.
14.
SawadaKTaneikeMKimuraKet al.Effect of nitrogen content on microstructural aspects and creep behavior in extremely low carbon 9Cr heat-resistant steel. ISIJ Int2004; 44: 1243–1249.
15.
PaulVTSarojaSHariharanPet al.Identification of microstructural zones and thermal cycles in a weldment of modified 9Cr-1Mo steel. J Mater Sci2007; 42: 5700–5713.
16.
ArivazhaganBPrabhuRAlbertSKet al.Microstructure and mechanical properties of 9Cr-1Mo steel weld fusion zones as a function of weld metal composition. J Mater Eng Perform2009; 18: 999–1004.
17.
P. Mac Ardghail, NUI Galway, personal communication; 2017.
18.
VijayalakshmiMSarojaSPaulVTet al.Microstructural zones in the primary solidification structure of weldment of 9Cr-1Mo steel. Metall Mater Trans A1999; 30: 161–174.
Dyson BF and Osgerby S. Modelling and analysis of creep deformation and fracture in a 1Cr 1/2Mo Ferritic Steel. Research DMM(A)116, August 1993. Teddington, UK: National Physical Laboratory.
21.
PerrinIJHayhurstDR. Creep constitutive equations for a 0.5Cr–0.5Mo–0.25V ferritic steel in the temperature range 600–675 ℃. J Strain Anal Eng Des1996; 31: 299–314.
22.
HydeTHBeckerAASunWet al.Finite-element creep damage analyses of P91 pipes. Int J Press Vessel Pip2005; 83: 853–863.
23.
OrugantiRKaradgeMSwaminathanS. Damage mechanics-based creep model for 9–10%Cr ferritic steels. Acta Mater2011; 59: 2145–2155.
24.
DysonB. Use of CDM in materials modelling and component creep life prediction. J Press Vessel Technol2000; 122: 281–296.
25.
RotersFRaabeDGottsteinG. Work hardening in heterogeneous alloys – a microstructural approach based on three internal state variables. Acta Mater2000; 48: 4181–4189.
26.
WatanabeTTabuchiMYamazakiMet al.Creep damage evaluation of 9Cr–1Mo–V–Nb steel welded joints showing Type IV fracture. Int J Press Vessel Pip2006; 83: 63–71.
27.
HydeTHSunWBeckerAAet al.Creep properties and failure assessment of new and fully repaired P91 pipe welds at 923K. Proc IMechE, Part L: J Materials: Design and Applications2004; 218: 211–222.
28.
HaneyEMDalleFSauzayMet al.Macroscopic results of long-term creep on a modified 9Cr–1Mo steel (T91). Mater Sci Eng A2009; 510–511: 99–103.
29.
Agyakwa P. Creep and microstructural development in P91 weldments at elevated temperature. PhD Thesis, University of Nottingham, UK, 2004.
30.
SpigarelliSQuadriniE. Analysis of the creep behaviour of modified P91 (9Cr–1Mo–NbV) welds. Mater Des2002; 23: 547–552.
31.
Barrett RA. Experimental characterisation and computational constitutive modelling of high temperature degradation in 9Cr steels including microstructural effects. PhD Thesis, National University of Ireland Galway, 2016.
32.
Gaffard V. Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments. PhD Thesis, Ecole Des Mines De Paris, France, 2004.
33.
MilovićLVuhererTBlačićIet al.Microstructures and mechanical properties of creep resistant steel for application at elevated temperatures. Mater Des2013; 46: 660–667.
34.
Abd El-AzimMENasreldinAMZiesGet al.Microstructural instability of a welded joint in P91 steel during creep at 600 ℃. Mater Sci Technol2005; 21: 779–790.
35.
BarbadikarDRDeshmukhGSMaddiLet al.Effect of normalizing and tempering temperatures on microstructure and mechanical properties of P92 steel. Int J Press Vessel Pip2015; 132–133: 97–105.
36.
Vivier F, Gourgues-Lorenzon A-F, Besson J, et al. Metallurgical properties and creep behaviour of a grade 91 steel base metal and weldment after short-term exposure at 500 ℃. In: ECCC conference on creep and fracture in high temperature components, design and life assessment issues, Dübendorf (Zürich), www.ommi.co.uk/PDF/Articles/204.pdf (2009, accessed 15 September 2017).
37.
MatsuiMTabuchiMWatanabeTet al.Degradation of creep strength in welded joint of 9%Cr steel. ISIJ Int2001; 41: 126–130.
38.
Tabuchi M and Takahashi Y. Evaluation of creep strength reduction factors for welded joints of modified 9Cr-1Mo steel. J Press Vessel Technol 2012; 134(3): 031401-034011-6.
39.
Kimura K and Takahashi Y. Evaluation of long-term creep strength of ASME grade 91, 92, and 122 type steels. In: ASME Paper No. PVP2012-78323. Canada: American Society of Mechanical Engineers, 2012.
40.
ASME Boiler & Pressure Vessel Code. Section III, Division 1, Subsection NH. New York, NY: American Society of Mechanical Engineers, 2004.
41.
OgataTSakaiTYaguchiM. Damage assessment method of P91 steel welded tube under internal pressure creep based on void growth simulation. Int J Press Vessel Pip2010; 87: 611–616.
42.
OgataTSakaiTYaguchiM. Damage characterization of a P91 steel weldment under uniaxial and multiaxial creep. Mater Sci Eng A2009; 510–511: 238–243.
43.
WatanabeTTabuchiMYamazakiMet al.Creep damage evaluation of 9Cr–1Mo–V–Nb steel welded joints showing Type IV fracture. Int J Press Vessel Pip2006; 83: 63–71.
44.
HydeTHSunW. Determining high temperature properties of weld materials. Solid Mech Mater Eng Int Ser A2000; 43: 40–414.
