Thermal creep properties of alloy D9 stainless steel and 316 stainless steel fuel clad tubes

• Published in: The International journal of pressure vessels and piping Vol. 85; no. 12; pp. 866 - 870
• Main Authors: Latha, S., Mathew, M.D., Parameswaran, P., Bhanu Sankara Rao, K., Mannan, S.L.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.12.2008; Elsevier
• Subjects: 316 SS clad tube; Alloy D9 SS clad tube; Applied sciences; Damage tolerance parameter; Ductility; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Installations for energy generation and conversion: thermal and electrical energy; Mechanical engineering. Machine design; Metals. Metallurgy; Steel design; Steel tanks and pressure vessels; boiler manufacturing; Stress exponent; Stress exponent; Alloy D9 SS clad tube; Damage tolerance parameter; 316 SS clad tube; Ductility; Work hardening; Creep; Pressure vessel; Creep strength; Dislocation; Grain boundary; Alloy steel; Creep fracture; Fuel rod; Rupture strength; Damaging; Recovery (properties); Cavitation; Thermal properties; Stainless steel-316; Break up time; Nuclear power plant; Stainless steel; Fast breeder; Fast reactor; Microstructure; Stainless steel-316L
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2008.07.002

Uniaxial thermal creep rupture properties of 20% cold worked alloy D9 stainless steel (alloy D9 SS) fuel clad tubes for fast breeder reactors have been evaluated at 973 K in the stress range 125–250 MPa. The rupture lives were in the range 90–8100 h. The results are compared with the properties of 20% cold worked type 316 stainless steel (316 SS) clad tubes. Alloy D9 SS were found to have higher creep rupture strengths, lower creep rates and lower rupture ductility than 316 SS. The deformation and damage processes were related through Monkman Grant relationship and modified Monkman Grant relationship. The creep damage tolerance parameter indicates that creep fracture takes place by intergranular cavitation. Precipitation of titanium carbides in the matrix and chromium carbides on the grain boundaries, dislocation substructure and twins were observed in transmission electron microscopic investigations of alloy D9 SS. The improvement in strength is attributed to the precipitation of fine titanium carbides in the matrix which prevents the recovery and recrystallisation of the cold worked microstructure.