Behavior Of AISI 316L Research Articles

Correlation between microstructure and intergranular corrosion behavior of low delta-ferrite content AISI 316L aged in the range 550–700 °C

Abstract The microstructure and the phase identification of austenitic stainless steel AISI 316L with low δ-ferrite content (δ ≤ 1%) and aged for up to 80 000 h at temperatures ranging from 550 to 700 °C were investigated by using an optical microscope (OM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Local changes of chromium content, resulting from nucleation and growth of chromium-rich phases during aging, were quantitatively assessed by energy dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscope (STEM). The intergranular corrosion behavior (IGC) of annealed and aged specimens was evaluated using the double loop electrochemical potentiokinetic reactivation (DL-EPR) and completed by IGC morphologies according to the ASTM A262 practice A standard. The results showed that δ-ferrite decomposed gradually into M 23 C 6 at 550 °C and decomposed totally into intermetallic phases (σ, η, χ, and R) and into secondary austenite (γ r ) at temperatures equal to or higher than 650 °C. Similarly γ-austenite decomposed into M 23 C 6 carbide at 550 °C and into intermetallic phases such as η and σ in addition to carbide, at higher temperatures. The time-temperature-sensitization diagram (TTS) was established and used to calculate the critical cooling rate (CCR) that prevents IGC sensitization. The analysis of IGC results leads to the conclusion that sensitization-desensitization is still controlled by the characteristics of chromium-depleted area surrounding austenite grain boundary regions. No significant effect of remained δ-ferrite and derived components on the corrosion behavior of AISI 316 L containing 1% of δ-ferrite.

Work Hardening and Tensile Behaviour of an Austenitic Stainless Steel at High Temperature

The work hardening and tensile behaviour of AISI 316L austenitic stainless steel deformed at temperatures between 600 and 1000°C has been investigated. The alloy has been heat-treated according two different roots: the first solutioning treatment was imposed at 1100°C and the second was designed at 875°C to reduce the dynamic ageing that occurs at temperatures up to 650°C in AISI 316L. In the solutionised material the work hardening data presented two linear regions: at high stresses the linearity has been described as the conventional Stage III of work hardening, whilst at low stresses the linearity has not been rationalised in any conventional stage of work hardening. In the second heat treatment alloy the work hardening data showed a single linear region at high stresses, whilst no linear stage occurred at low stresses. Therefore, the work hardening and tensile behaviour of AISI 316L has resulted to be significantly affected by the two different heat treatments and dynamic aging has been proved to influence work hardening behaviour well beyond the range of temperatures in which serrated yielding occurs.

Tensile deformation behaviour of AISI 316L(N) SS

Tensile deformation behaviour of AISI 316L(N) stainless steel was investigated over the range 298 to 1023 K. The yield and tensile strength were found to meet the minimum values mandated by RCC-MR, the French design code for fast reactors. The tensile flow behaviour was modelled using Ludwigson and Voce equation. Ludwigson equation could model the flow behaviour adequately before the onset of saturation at temperatures >823 K. Voce equation could model the flow behaviour between 298 and 1023 K. The physical basis for the variation with respect to strain rate and temperature of the constants obtained by modelling the flow curve using Ludwigson and Voce equation is discussed.

Corrosion Fatigue of 316L Stainless Steel in Hot LiOH Solution

Abstract The corrosion fatigue behavior of AISI 316L (UNS S31603) stainless steel was tested in concentrated aqueous lithium hydroxide solutions at elevated temperature. Fatigue tests were conducted in a 10 g LiOH/100cc H2O solution at 95°C at controlled electrochemical potentials. Experimental conditions met requirements of the aqueous Li salt blanket option for the international and European nuclear fusion reactor programs of the International Thermonuclear Experimental Reactor (ITER) and Next European Torus (NET). Results indicated 316L stainless steel was susceptible to corrosion fatigue in a narrow potential range of approximately 100 mV (vs SCE). Tests at lower or higher potentials (e.g., −80 and 200 mV), however, did not show susceptibility to corrosion fatigue cracking. Results were compared with the stress corrosion cracking behavior of 316L in the same environment.