Effect of Inhomogeneity of Carbide Precipitation on Nanohardness Distribution for Martensitic Steels

Abstract:

Nanoindentation technique was applied to evaluate nanohardness distribution in a submicron scale for two kinds of martensitic steels: Fe-0.4C binary steel and Fe-0.05C-0.22Ti steel with a stoichiometric composition of TiC. AFM images showed that Fe-C steel includes relatively coarse cementite particles with about 100~200 nm in diameter and a couple of hundreds nanometer in average spacing, while high-resolution TEM observation showed that the Fe-C-Ti steel has fine TiC precipitates with 5 nm in diameter and 15 nm for average spacing. Nanoindentation results revealed that the standard deviation was much higher for the Fe-C than that for the Fe-C-Ti. Since the typical indent size was a couple of hundreds nanometer, which was about two orders larger than the size of the TiC and comparable to the cementite size, the small distribution of nanohardness of the Fe-C-Ti was attributed to the homogeneous microstructure in sub-micron scale, while the inhomogeneity of cementite particles in the Fe-C steel leaded to large nanohardness.

• Periodical: Materials Science Forum (Volumes 475-479)
• Pages: 4109-4112
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.475-479.4109
• Online since: January 2005
• Authors: Jin Xu Li, Takahito Ohmura, Fu Gao Wei, Kaneaki Tsuzaki
• Keywords: Carbide Precipitate, Hardness Distribution, Martensitic Steel

References

[1] A.R. Marder and G. Krauss: Transactions of the ASM, Vol. 60(1967), p.651.

[2] A.R. Marder and G. Krauss: Transactions of the ASM, Vol. 62(1969), p.957.

[3] T. Ohmura, K. Tsuzaki and S. Matsuoka: Phil. Mag. A, Vol. 82(2002), p. (1903).

[4] T. Ohmura, K. Tsuzaki and S. Matsuoka: Scripta Mater. Vol. 49(2003), p.1157.

[5] J. Li, T. Ohmura, M. Murayama and K. Tsuzaki, Proceeding of International conference on advanced technology in experimental mechanics 2003, Nagoya, Japan, p.108.

[6] J. Li, T. Ohmura, M. Murayama and K. Tsuzaki, Proceedings of second international conference on advanced structural steels, 2004, Shanghai, China, p.630.

[7] C. Oliver and G. M. Pharr: J. Mater. Res., Vol. 7(1992), p.1564.

[8] S. Takaki: Nishiyama memorial lecture (ISIJ, Japan, 1992).

[9] Y. Murakami and M. Itokazu: Int. J. Solids Structures, Vol. 34(1997), p.4005. Fig. 5 Histogram of micro- Vickers hardness for (a) the Fe-C-Ti and (b) the Fe-C martensite tested at load of 9. 8 N.