Austenitic stainless steels predictions

Auscor Prediction of corrosion of austenitic stainless steels UK Savior... 

The effects of quench rate on IGC for Al-Gu, Al-Gu-Mg, and Al-Cu-Mg-Mn alloys as well as for austenitic stainless steels is considered to be well-understood [43, 74, 75, 106]. Integration of the effects of precipitation and solute depletion at each temperature during a quench (i.e., quench factor analysis) can be compared to isothermal time-temperature-sensitization diagrams in order to predict the quench rate required to avoid IGC [43, 74]. Alloys... 

Strain-induced martensite has been found to increase with decreasing temperature and increasing plastic strain in austenitic stainless steels [1]. Consequently, the reported low-temperature martensite suppression may be predictable in terms of the existing theory since the corresponding plastic strain also decreased substantially. However, there is also the possibility that the martensitic transformation is suppressed at very low temperatures in these alloys independently of the strain. 

E.J. Opila, N.S. Jacobson, D.L. Myers, and E.H. Copland, Predicting oxide stability in high-temperature water vapor, Journal of the Minerals, Metals, and Materials Society 58 22-28, 2006 I. Kvernes, M. Oliveira, and P. Kofstad, High temperature oxidation of Fe-13Cr xAl alloys in air/water vapor mixtures, Corrosion Science 17 237-52, 1977 H. Asteman, J.-E. Svensson, M. Norrell, and L.-G. Johansson, Influence of water vapor and flow rate on the high-temperature oxidation of 304L Effect of chromium oxide hydroxide evaporation. Oxidation of Metals 54 11-26,2000 J.M. Rakowski and B.A. Pint, Observations on the effect of water vapor on the elevated temperature oxidation of austenitic stainless steel foil. Proceedings of Corrosion 2000, NACE Paper 00-517, NACE International, Houston, Texas, 2000 E. Essuman, G.H. Meier, J. Zurek, M. Hansel, and W.J. Quadakkers, The effect of water vapor on selective oxidation of Fe-Cr Alloys, Oxidation of Metals 69 143-162,2008 E.J. Opda, Oxidation and volatilization of silica formers in water vapor. Journal of the American Ceramic Society 86(8) 1238-1248,2003. 

FIG. 11—Neural network architecture for the prediction of SCC rlek of austenitic stainless steels in industrial processes. 

There have been well-documented instances of environmentally assisted cracking in high-temperature water of austenitic stainless steels, nickel-base alloys, low-alloy and carbon steels, and their weld metals in various subcomponents of pressure vessels, pressurizers, steam generators, piping, deaerators, etc. Consequently, there is a strong driving force to derive design and life prediction codes which can account for... 

R. Nishimura, K. Kudo, Stress corrosion cracking of AISI 304 and AISI 316 austenitic stainless steels in HCl and H2SO4 solutions - prediction of time-to-failure and criterion for assessment of SCC susceptibility. Corrosion, (1989) 308-316. 

H. Leinonen, Stress corrosion cracking and life prediction evaluation of austenitic stainless steels in calcium chloride solution. Corrosion, 52(5) (1996) 337-346. 

H. Leinonen, 1. Virkkunen, H. Hanninen, Stress corrosion cracking and life prediction of austenitic stainless steels in calcium chloride solution, in Hydrogen Effects on Material Behavior and Corrosion Deformation Interactions, Proc. Int. Conf, Moran, WY, USA, 22-26 Sept. 2002 (2003) 673-682. 

One of the main challenges for some reactor components in austenitic stainless steels at high-temperature in-service conditions is the demonstration of their behavior up to 60 years. The evaluation of creep lifetime of these stainless steels requires on the one hand to carry out very long-term creep tests and on the other hand to understand and model the damage mechanisms in order to propose physically based predictions toward 60 years of service. 

Experimental creep failure stress—lifetime curves of the steel 316L(N) are plotted for tests carried out at temperatures between 525 and 700°C (Fig. 6.3). The extrapolation of these curves based on high-stress data leads to overestimated lifetimes. For example, the extrapolation of a curve at 700° C differs by a factor of 10 at low stress with respect to available experimental data. Therefore, long-term creep lifetimes cannot be predicted by the extrapolations based on short-term data. Similar conclusions have been drawn for ferritic-martensitic steels. But it should be highlighted that this transition occurs much earlier in austenitic stainless steels. The comparison of Figs. 6.23 and 6.24 shows that the transition time is about 4 years in austenitic stainless steels but reaches at least 10 years in tempered martensite-ferritic steels. 

Figure 6.32 Comparison between experimental lifetimes and predicted ones. The necking model is used at high stress whereas the Riedel intergranular damage is used at low stress (high-stress regime of strain rates) and very low stress (low-stress regime of strain rates), (a) Material A (b) material B. Experimental data found in Ref [103]. Advanced austenitic stainless steel, Fe35Ni25CrNb, 980°C.

Interestingly, even if the microstructural evolutions are different, advanced austenitic stainless steels and the Incolloy 800 alloy, which is close to nickel-based alloys, are subjected to the same creep damage mechanisms as martensitic steels and conventional austenitic stainless steels. The same modelings may be applied and lead to creep lifetime predictions in agreement with experimental data up to the longest experimental lifetimes published in the literamre. 

Such predictions may provide inputs for fatigue-relaxation damage modeling, which should he based on the synergy between oxidation and oxide layer fracture in tempered martensite-ferritic steels but creep cavitation in austenitic stainless steels. 

D. Argence, A. Pineau, Predictive metallurgy applied to creep-fatigue damage of austenitic stainless steels, in Proc. of the Donald McLean Symposium, Structural Materials, The Institute of Materials, 1995, pp. 229—257. 

AUSCOR UK SAVOIR Prediction (austenitic stainless steels) 6 825 ... 

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