The effect of nitrogen alloying (0.078% to 0.22%) in 316 LN stainless steel has been investigated for its Low Cycle Fatigue properties in the temperature range 300 to 873 K. The effect of dynamic strain ageing has been evaluated as a function of nitrogen content, temperature, strain amplitude and strain rate. The temperature range of operation of DSA has been found to be a strong function of the above parameters. Increase in nitrogen content shifted the range of operation of DSA to higher temperatures. For temperatures ≤673 K, fatigue life is found to be maximum for a nitrogen content of 0.14 wt%, while it is found to saturate or increase with increasing nitrogen content at temperatures <673 K. © 2010 Published by Elsevier Ltd.

S. Sankaran

Department of Metallurgical and Materials Engineering

G.V. Prasad Reddy

R. Sandhya

K. Bhanu Sankara Rao

AISI 316

Dynamic strain ageing

Fatigue life

Higher temperatures

LOW CYCLE FATIGUE PROPERTIES

LOW CYCLE FATIGUES

NITROGEN ALLOYING

Nitrogen content

ON dynamics

STRAIN AMPLITUDE

Temperature range

Alloying

ANALOG DIFFERENTIAL ANALYZERS

Austenite

Austenitic stainless steel

Corrosion resistant alloys

nitrogen

Strain rate

Fulltext

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IIT Madras

Procedia Engineering

The effect of strain rate and nitrogen content on cyclic deformation and substructural changes in 316LN stainless steel is investigated at temperatures 773, 823 and 873 K. Dynamic strain aging (DSA) and/or thermal-recovery processes are observed to control cyclic deformation, and the regimes of their predominance are mapped. An increase in nitrogen content and DSA enhanced cyclic stress and are found to offset thermal-recovery induced cyclic strength reduction. In addition, strain localization in the form of slip-bands impinging on grain boundary is observed. The predominance of thermal-recovery over DSA manifested as dislocation-poor channels, dislocation cells within and in-between planar slip-bands. © 2015 Elsevier Ltd. All rights reserved.

International Journal of Fatigue

Effect of strain rate on low cycle fatigue of 316LN stainless steel with varying nitrogen content: Part-I cyclic deformation behavior

Thermomechanical (TMF) and isothermal (IF) fatigue behavior of 316LN stainless steel alloyed with 0.07, 0.14, and 0.22&nbsp;wt&nbsp;pct nitrogen is presented in this manuscript. In the TMF tests with temperature cycling in the range of 573&nbsp;K to 873&nbsp;K (300&nbsp;°C to 600&nbsp;°C), life decreased with increasing nitrogen content for both in-phase (IP) and out-of-phase (OP) cycling, with a peak at 0.07&nbsp;wt&nbsp;pct N. In contrast, 0.14&nbsp;wt&nbsp;pct N yielded maximum life under IF cycling carried out at 873&nbsp;K (600&nbsp;°C). Cyclic lives are seen to follow the sequence, IP-TMF&nbsp;&lt;&nbsp;IF&nbsp;&lt;&nbsp;OP-TMF cycling, and it remained same irrespective of the nitrogen content in 316LN SS. Lives under IP-TMF are lower than those in OP cycling by a factor of 2 to 2.5, in spite of the higher cyclic stress response in OP cycling. At all the nitrogen contents in the present study, nitrogen and dynamic strain aging induced slip localization in the form of planar slip bands both in IP and OP-TMF, in comparison to IF deformation wherein complete planar slip mode of deformation is evidenced only at 0.22&nbsp;wt&nbsp;pct N. In TMF studies, increasing nitrogen content promoted strong slip localization (i.e., increase in slip band density with a decrease in interband spacing) in combination with high tensile cyclic stresses that marred the beneficial effect of nitrogen content on TMF life. © 2014, The Minerals, Metals &amp; Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Thermomechanical and Isothermal Fatigue Behavior of 316LN Stainless Steel with Varying Nitrogen Content

In this study, the influence of cyclic strain amplitude on the evolution of cyclic stress-strain response and the associated cyclic deformation mechanisms in 316LN stainless steel with varying nitrogen content (0.07 to 0.22 wt pct) is reported in the temperature range 773 K to 873 K (500 °C to 600 °C). Two mechanisms, namely dynamic strain aging and secondary cyclic hardening, are found to strongly influence the cyclic stress response. Deformation substructures associated with both the mechanisms showed planar mode of deformation. These mechanisms are observed to be operative over certain combinations of temperature and strain amplitude. For strain amplitudes >0.6 pct, wavy or mixed mode of deformation is noticed to suppress both the mechanisms. Cyclic stress-strain curves revealed both single and dual-slope behavior depending on the test temperature. Increase in nitrogen content is found to increase the tendency toward planar mode of deformation, while increase in strain amplitude leads to transition from planar slip bands to dislocation cell/wall structure formation, irrespective of the nitrogen content in 316LN stainless steel. © 2014 The Minerals, Metals & Materials Society and ASM International.

Low cycle fatigue behavior of 316LN stainless steel alloyed with varying nitrogen content. Part I: Cyclic deformation behavior

Influence of nitrogen content on low cycle fatigue life and fracture behavior of 316LN stainless steel (SS) alloyed with 0.07 to 0.22 wt pct nitrogen is presented in this paper over a range of total strain amplitudes (±0.25 to 1.0 pct) in the temperature range from 773 K to 873 K (500 °C to 600 °C). The combined effect of nitrogen and strain amplitude on fatigue life is observed to be complex i.e., fatigue life either decreases/increases with increase in nitrogen content or saturates/peaks at 0.14 wt pct N depending on strain amplitude and temperature. Coffin-Manson plots (CMPs) revealed both single-slope and dual-slope strain-life curves depending on the test temperature and nitrogen content. 316LN SS containing 0.07 and 0.22 wt pct N showed nearly single-slope CMP at all test temperatures, while 316LN SS with 0.11 and 0.14 wt pct N exhibited marked dual-slope behavior at 773 K (500 °C) that changes to single-slope behavior at 873 K (600 °C). The changes in slope of CMP are found to be in good correlation with deformation substructural changes. © 2014 The Minerals, Metals & Materials Society and ASM International.

Low cycle fatigue behavior of 316LN stainless steel alloyed with varying nitrogen content. Part II: Fatigue life and fracture behavior

In this article, the occurrence of secondary cyclic hardening (SCH) and its effect on high-temperature cyclic deformation and fatigue life of 316LN Stainless steel are presented. SCH is found to result from planar slip mode of deformation and enhance the degree of hardening over and above that resulted from dynamic strain aging. The occurrence of SCH is strongly governed by the applied strain amplitude, test temperature, and the nitrogen content in the 316LN SS. Under certain test conditions, SCH is noticed to decrease the low cycle fatigue life with the increasing nitrogen content. © The Minerals, Metals &amp; Materials Society and ASM International 2013.

Influence of secondary cyclic hardening on the low cycle fatigue behavior of nitrogen alloyed 316LN Stainless steel

Strain-controlled low cycle fatigue tests have been conducted in air between 298-873 K to ascertain the influence of temperature on LCF behaviour of nitrogen-alloyed type 316L stainless steel. A strain amplitude of ± 0.60% and a symmetrical triangular waveform at a constant strain rate of 3 × 10-3 s-1 were employed for all tests. Crack initiation and propagation modes were evaluated, and the deformation and damage mechanisms which influence the cyclic stress response and fatigue life identified. The cyclic stress response at all temperatures was characterized by an initial hardening to the maximum stress, followed by gradual softening prior to attaining saturation. Temperature dependence of fatigue life showed a maximum in the intermediate temperature range. The drastic reduction in fatigue life at elevated temperatures has been ascribed primarily to the combined influence of dynamic strain ageing effects and oxidation-enhanced crack initiation, while the lower life at room temperature is attributed to detrimental effects associated with deformation-induced martensite. © 1991.

Effects of temperature on the low cycle fatigue behaviour of nitrogen alloyed type 316L stainless steel

Journal of Nuclear Materials

Effects of nitrogen on low-cycle fatigue properties of type 304L austenitic stainless steels tested with and without tensile strain hold

Materials Science Forum

The Neutron-Spectroscopy Proof of the Strong Cr-N Interactions in Nitrogen Stainless Steels

Effect of nitrogen on high temperature low cycle fatigue behaviors in type 316L stainless steel

Scripta Materialia

The influence of dynamic strain ageing on stress response and strain-life relationship in low cycle fatigue of 316L(N) stainless steel

Influence of nitrogen alloying on dynamic strain ageing regimes in low cycle fatigue of AISI 316LN stainless steel

Journal	Procedia Engineering
ISSN	18777058
Open Access	Yes