Time–temperature-sensitization diagrams and critical cooling rates of different nitrogen containing austenitic stainless steels

• Published in: Journal of nuclear materials 2010-04, Vol.399 (1), p.62-67
• Main Authors: Parvathavarthini, N., Dayal, R.K.
• Format: Article
• Language: English
• Subjects: Applied sciences; Austenitic stainless steel; Austenitic stainless steels; Controled nuclear fusion plants; Cooling rate; Critical cooling rates; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Heat resistant steels; Heat treatment; Installations for energy generation and conversion: thermal and electrical energy; Nuclear engineering; Nuclear fuels; Nuclear power generation; Nuclear reactor components; Nuclear reactors; Sensitization; Stainless steels; TTS diagrams
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2010.01.003

Nitrogen-alloyed 316L stainless steel is being used as structural material for high temperature fast breeder reactor components with a design life of 40 years. With a view to increase the design life to 60 years and beyond, high nitrogen stainless steels are being considered for certain critical components which may be used at high temperatures. Since carbon and nitrogen have major influence on the sensitization kinetics, investigations were carried out to establish the sensitization behaviour of four heats of 316L SS containing (i) 0.07%N and 0.035%C, (ii) 0.120%N and 0.030%C, (iii) 0.150%N and 0.025%C and (iv) 0.22%N and 0.035%C. These stainless steels were subjected to heat treatments in the temperature range of 823–1023 K for various durations ranging from 1 h to 500 h. Using ASTM standard A262 Practice A and E tests, time–temperature-sensitization diagrams were constructed and from these diagrams, critical cooling rate above which there is no risk of sensitization was calculated. The data established in this work can be used to select optimum heat treatment parameters during heat treatments of fabricated components for fast reactors.