The effect of long-term thermal exposure at elevated temperatures on microstructures and mechanical properties in centrifugally casted iron-base alloy

Authors

  • Gobboon Lothongkum Faculty of Engineering Chulalongkorn University
  • Natthasit Thaweepornkhasemsukh Faculty of Engineering Chulalongkorn University
  • Panyawat Wangyao Metallurgy and Materials Science Research Institute (MMRI), Chulalongkorn University

Keywords:

Iron-base alloy, Heat treatment, Aging, Carbide precipitation, Mechanical properties, Microstructure

Abstract

This work has an aim to study and investigate the relationship between high temperature exposure conditions on microstructural evolution and mechanical properties in the iron-based alloy, Fe-30.8 Ni 26.6 Cr alloy, strengthened by carbide precipitation. Two exposure temperatures (900 and 1000°C) with various thermal exposure times are introduced to the as-received alloy. After short-term exposure, it was found that the secondary carbides precipitated early near the primary carbides, which were chromium and niobium/titanium carbide networks. The secondary carbide precipitations were also found in the dendrite cores. The amounts of needle-like carbides and secondary carbide films increased with time and temperature of aging. However, by EDS analysis, the composition of secondary carbides was almost the same as that of primary carbides for 24 hours heating time. However, they continued to change when thermal exposure time increased. It can be summarized that the exposure conditions have effect on shape, size, dispersion and the location of secondary carbides in microstructure and result in the different mechanical properties such as hardness and tensile strength. Under exposure at 900°C, the very fine precipitates of secondary carbide particles located and concentrate in the area close to primary carbide. In case exposure at 1000°C, the coarser secondary carbides dispersed to the cores of dendrites. The needle-like and film carbides were found in heat-treated specimens at both temperatures. The precipitated secondary carbides precipitated after longterm exposure conditions were chromium carbides, which its chemical composition was similar to primary chromium carbide. It could be concluded that the uniform precipitation and dispersion of fine secondary carbides resulted in slightly higher ultimate tensile and yield strengths as well as hardness in the short-term aging. Then both hardness of tensile strength slightly decreased.

Downloads

Download data is not yet available.

References

de Alumeida, H.L., Ribeiro, A.F. and Le May, I. 2002. Microstructural characterization of modified 25Cr-35Ni centrifugally cast steel furnace tubes. Mater. Character. 49 (3) : 219 – 229.

Ratanamahasakul, S., Lothongkum, G. and Wangyao, P. 2004. Effect of aging conditions on microstructure and mechanical properties in iron-based alloy. J. Met. Mater. Miner. 14 (1) : 39-48.

Rodriguez, J., Haro, S., Velasco, A. and Colas, R.2000. A Metallographic study of aging in cast heat-resisting alloy. Mater. Character. 45 : 23 – 32.

de Almeida, L. H., Ribeiro, A. F. and Le May, I. 2002. Microstructura characterization of modified 25Cr-35Ni centrifugally cast steel furnace tubes. Mater. Character. 49 (3) : 219 – 229.

Kaya, A.A., Krauklis, P. and Young, D.J. 2002. Microstructure of HK40 alloy after high temperature service in oxidizing/ carburizing environment, I. Oxidation phenomena and propagation of a crack. Mater.Character. 49 (1) : 11 – 21.

Wu, X. Q., Jing, H. M., Zheng, Y. G., Yao, Z.M., Ke, W. and Hu, Z. Q. 2000. The eutectic of carbides and creep rupture strength of 25Cr 20Ni heat resistant steel tubes centrifugally cast with different solidification conditions. Mater. Sci. Eng. A 293 (1-2) : 252 – 260.

Piekarski, B. 2001. Effect of Nb and Ti additions on microstructure and identification of precipitates in stabilized Ni-Cr cast austenitic steels. Mater. Character. 47 : 181 – 186.

Ibanez, R. A. P., de Almeida Soares, G. D., de Almeida, L. H. and Le May, I 1993. Effects of Si content on the microstructure of modified-HP austenitic steels. Mater.Character. 30 : 43 – 49.

Barbabela, G. D., de Almeida, L. H., da Silveira, T.L. and Le May, I. 1991. Role of Nb in modifying the microstructure of heatresistant cast HP steel. Mater. Character.. 26 : 193 – 197.

Barbabela, G. D., de Almeida, L.H., da Silveira, T.L. and Le May, I. 1992. Niobium additions in HP heat-resistant cast stainless steel. Mater. Character. 26 : 387 – 396.

Kenik, E. A., Maziasz, P. J. Swindeman, R. W., Cervenka, J. and May, D. 2003. Structure and Phase stability in a cast modified-HP austenite after long-term ageing. Scripta Mater. 49 (2) : 117 – 122.

Barbabela, G. D., de Almeida, L. H., da Silveira, T. L. and Le May, I. 1991. Phase characterization in Two Centrifugally Cast HK steel tubes. Mater. Character. 26 : 1 - 7.

Downloads

Published

2017-04-16

How to Cite

[1]
G. . Lothongkum, N. Thaweepornkhasemsukh, and P. Wangyao, “The effect of long-term thermal exposure at elevated temperatures on microstructures and mechanical properties in centrifugally casted iron-base alloy”, J Met Mater Miner, vol. 16, no. 2, Apr. 2017.

Issue

Section

Original Research Articles

Most read articles by the same author(s)

1 2 3 4 > >>