Microstructural evolution and mechanical properties of an Fe–18Ni–16Cr–4Al base alloy during aging at 950°C

Abstract

The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe–18Ni–16Cr–4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950°C were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

Keywords

austenitic steel / alumina / aging / precipitates / mechanical properties / microstructural evolution / nuclear power plants

References

[1] Viswanathan R., Bakker W. Materials for ultrasupercritical coal power plants- turbine materials: part II. J. Mater. Eng. Perform., 2001, 10(1): 96.

[2] Viswanathan R., Coleman K., Rao U. Materials for ultra-supercritical coal-fire power plant boilers. Int. J. Pressure Vessels Piping, 2006, 83(11-12): 778.

[3] Murty K.L., Charit I. Structural materials for Gen nuclear reactors: challenges and opportunities. J. Nucl. Mater., 2008, 383(1-2): 189.

[4] Viswanathan R., Sarver J., Tanzosh J.M. Boiler materials for ultra-supercritical coal power plants: steamside oxidation. J. Mater. Eng. Perform., 2006, 15(3): 255.

[5] Ramakrishnan V., McGurty J.A., Jayaraman N. Oxidation of high-aluminum austenitic stainless steels. Oxid. Met., 1988, 30(3): 185.

[6] Zhang Y.D., Zhang C., Lan H., Hou P.Y., Yang Z.G. Improvement of the oxidation resistance of Tribaloy T-800 alloy by the additions of yttrium and aluminium. Corros. Sci., 2011, 53(3): 1035.

[7] McGurty J.A. Austenitic Iron Alloys, 1973

[8] Suryanarayana C. Mechanical alloying and milling. Prog. Mater. Sci., 2001, 46(1-2): 1.

[9] Sakasegawa H., Legendre F., Boulanger L., Brocq M., Chaffron L., Cozzika T., Malaplate J., Henry J., de Carlan Y. Stability of non-stoichiometric clusters in the MA957 ODS ferrtic alloy. J. Nucl. Mater., 2011, 417(1-3): 229.

[10] Wang M., Zhou Z.J., Sun H.Y., Hu H.L., Li S.F. Microstructural observation and tensile properties of ODS-304 austenitic steel. Mater. Sci. Eng. A, 2013, 559, 287.

[11] Wey M.Y., Sakuma T., Nishizawa T. Growth of alloy carbide particles in austenite. Trans. Jpn. Inst. Met., 1981, 22(10): 733.

[12] Taneike M., Abe F., Sawada K. Creep-strengthening of steel at high temperatures using nano-sized carbonitride dispersions. Nature, 2003, 424, 294.

[13] Maziasz P.J., Shingledecker J.P., Evans N.D. Developing new cast austenitic stainless steels with improved high-temperature creep resistance. J. Pressure Vessel Technol., 2009, 131, 1.

[14] Sawada K., Kubo K., Abe F. Creep behavior and stability of MX precipitates at high temperature in 9Cr-0.5Mo-1.8W-VNb steel. Mater. Sci. Eng. A, 2001, 319-321, 784.

[15] Maziasz P.J. Developing an austenitic stainless steel for improved performance in advanced fossil power facilities. JOM, 1989, 41(7): 14.

[16] Jahazi M., Jonas J.J. The non-equilibrium segregation of boron on original and moving austenite grain boundaries. Mater. Sci. Eng. A, 2002, 335(1-2): 49.

[17] Satyanarayana D.V.V., Malakondaiah G., Sarma D.S. Steady state creep behaviour of NiAl hardened austenitic steel. Mater. Sci. Eng. A, 2002, 323(1-2): 119.

[18] Muneki S., Okada H., Okubo H., Igarashi M., Abe F. Creep characteristics in carbon free new martensitic alloys. Mater. Sci. Eng. A, 2005, 406(1-2): 43.

[19] Yamamoto Y., Takeyama M., Lu Z.P., Liu C.T., Evans N.D., Maziasz P.J., Brady M.P. Alloying effects on creep and oxidation resistance of austenitic stainless steel alloys employing intermetallic precipitates. Intermetallics, 2008, 16(3): 453.

[20] Chen S.W., Zhang C., Xia Z.X., Ishikawa H., Yang Z.G. Precipitation behavior of Fe2Nb Laves phase on grain boundaries in austenitic heat resistant steels. Mater. Sci. Eng. A, 2014, 616, 183.

[21] Brady M.P., Magee J., Yamamoto Y., Helmick D., Wang L. Co-optimization of wrought alumina-forming austenitic stainless steel composition ranges for high-temperature creep and oxidation/corrosion resistance. Mater. Sci. Eng. A, 2014, 590, 101.

[22] Yamamoto Y., Brady M.P., Lu Z.P., Maziasz P.J., Liu C.T., Pint B.A., More K.L., Meyer H.M., Payzant E.A. Creep-resistant, Al2O₃-forming austenitic stainless steels. Science, 2007, 316(5823): 433.

[23] Yamamoto Y., Brady M.P., Lu Z.P., Liu C.T., Takeyama M., Maziasz P.J., Pint B.A. Alumina-forming austenitic stainless steels strengthened by Laves Phase an MC carbide precipitates. Metall. Mater. Trans. A, 2007, 38(11): 2737.

[24] Bei H., Yamamoto Y., Brady M.P., Santella M.L. Aging effects on the mechanical properties of alumina-forming austenitic stainless steels. Mater. Sci. Eng. A, 2010, 527(7-8): 2079.

[25] Brady M.P., Wright I.G., Gleeson B. Alloy design strategies for promoting protective oxide-scale formation. JOM, 2000, 52(1): 16.

[26] Brady M.P., Unocic K.A., Lance M.J., Santella M.L., Yamamoto Y., Walker L.R. Increasing the upper temperature oxidation limit of alumina forming austenitic stainless steels in air with water vapor. Oxid. Met., 2011, 75(5): 337.

[27] Xu X.Q., Zhang X.F., Chen G.L., Lu Z.P. Improvement of high-temperature oxidation resistance and strength in alumina- forming austenitic stainless steels. Mater. Lett., 2011, 65(21-22): 3285.

[28] Fullman R.L., Fisher J.C. Formation of annealing twins during grain growth. J. Appl. Phys., 1951, 22(11): 1350.

[29] Shimada M., Kokawa H., Wang Z.J., Sato Y.S., Karibe I. Optimization of grain boundary character distribution for intergranular corrosion resistant 304 stainless steel by twin- induced grain boundary engineering. Acta Mater., 2002, 50(9): 2331.