Effect of Mo on mechanical properties of modified ultrahigh carbon steels after heat-treatment

Abstract

Microstructure and mechanical properties of modified ultrahigh carbon (1.6%C) steels with different Mo additions (0, 0.3%, 0.5%, and 0.8%, mass fraction) were studied in their as-cast and quenched then tempered conditions by optical microscopy, scanning electronic microscopy, X-ray diffraction and hardness and toughness tests, respectively. The results show that the continuous eutectic carbide network structure has been broken down and changed to partial isolated and finer particles embedded in matrix of as-cast alloy by modification. Carbides in both quenched and tempered specimens have been refined effectively after the addition of Mo. Specimen containing 0.5% Mo shows the finest microstructures with carbides dispersed homogeneously in martensite matrix and demonstrates highest impact toughness of 18.4 J/cm² and hardness of 50 HRC.

Keywords

ultrahigh carbon steel / molybdenum / microstructure / impact toughness / hardness

References

[1] Victoria-HernándezJ, Hernández-SilvaD, Vite-TorresM. Microstructural characterization and sliding wear behavior of ultra high carbon steels processed by mechanical alloying [J]. Wear, 2009, 267(1/2/3/4): 340-344

[2] WadsworthJ, LesuerD R. Ancient and modern laminated composites from the great pyramid of gizeh to Y2K [J]. Materials Characterization, 2000, 45(4/5): 289-313

[3] LesuerD R, SynC K, GoldbergA, WadsworthJ, SherbyO D. The case for ultrahigh carbon steels as structural materials [J]. Journal of the Minerals, Metals and Materials Society, 1993, 45(8): 40-46

[4] OyamaT, SherbyO D, WadsworthJ, WalserB. Application of the divorced eutectoid transformation to the development of fine-grained, spheroidized structures in ultrahigh carbon steels [J]. Scripta Metallurgica, 1984, 18(8): 799-804

[5] MaQ, LiuB C, WangZ C. Breakup of eutectic carbide network of white cast irons at high temperatures [J]. Journal of Materials Science, 1995, 30(13): 3383-3386

[6] ZhangZ L, LiuY N, ZhuJ W, YuG. Processing and properties of ultrahigh-carbon (1.6%C) steel [J]. Materials Science and Engineering A, 2008, 483–484: 64-66

[7] PowellG L F, CarlsonR A, RandleV. The morphology and microtexture of M7C3 carbides in Fe-Cr-C and Fe-Cr-C-Si alloys of near eutectic composition [J]. Journal of Materials Science, 1994, 29(18): 4889-4896

[8] PengH F, SongX Y, GaoA G, MaX L. Microstructure and mechanical properties of the Al-added ultrahigh carbon steel [J]. Materials Letters, 2005, 59(26): 3330-3332

[9] LiuK P, DunX L, LaiJ P, LiuH S. Effects of modification on microstructure and properties of ultrahigh carbon (1.9% C) steel [J]. Materials Science and Engineering A, 2011, 528: 8263-8268

[10] WanR C, SunF, ZhangL T, ShanA D. Effect of Mo on high-temperature strength of fire-resistant steel [J]. Materials and Design, 2012, 35: 335-341

[11] BholeS D, NemadeJ B, CollinsL, LiuC. Effect of nickel and molybdenum additions on weld metal toughness in a submerged arc welded HSLA line-pipe steel [J]. Journal of Materials Processing Technology, 2006, 173(1): 92-100

[12] PinedaE, BrunaP, SerranoJ, Torrens-serraJ, CrespoD. Roll of Mo in the local configuration and structure stabilization of amorphous steels, a synchrotron X-ray diffraction and Mossbauer study [J]. Journal of Alloys and Compounds, 2011, 509S: 56-59

[13] WeiW, ShanY Y, YangK, WangY Q. Effects of combined addition of Mo-B on transformed microstructure of ultrahigh-strength pipeline steels [J]. Acta Metallurgica Sinica, 2007, 43: 943-948

[14] ShaeriM H, SaghafianH, ShabestariS G. Effects of austempering and martempering processes on amount of retained austenite in Cr-Mo steels (FMU-226) used in mill liner [J]. Journal of Iron and Steel Research International, 2010, 17(2): 53-58

[15] ZhuY Z, ZhuZ, YinZ M, XiangZ D. Evolution of carbides and carbon content in matrix of an ultra-high carbon sintered steel during heat treatment process [J]. International Journal of Minerals, Metallurgy and Materials, 2009, 16(3): 299-303

[16] ParkS G, KimM C, LeeB S, WeeD M. Correlation of the thermodynamic calculation and the experimental observation of Ni-Mo-Cr low alloy steel changing Ni, Mo, and Cr contents [J]. Journal of Nuclear Materials, 2010, 407(2): 126-135