Research on the Microstructure and Properties of Laser Cladding Fe&mdash;base Alloy on U71 MU Rail Surface

YANG Jiao—xi; LIU Hua—dong

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Journal of Railway Engineering Society ›› 2010, Vol. 27 ›› Issue (7) : 34-37.

Research on the Microstructure and Properties of Laser Cladding Fe—base Alloy on U71 MU Rail Surface

YANG Jiao—xi，LIU Hua—dong

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Abstract

Research purposes: With much increase of train running speed，the higher properties of weal"一resistance and rolling contact fatigue—resistance are required to the rail．For increasing service life of the rail，the surface of U7 1 Mn rail Was strengthened by wide—band laser cladding technique．In order to obtain high—performance about 1 mm thick coating free of cracks and pores that metallurgically bonded with the rail matrix，the cladding process Was conducted by C02 laser with direct injection of the Fe—based powder into the molten p001．

Research conclusions: The results of experiments and analysis showed that high quality cladding coating with the thickness of about 1 mm can be obtained under the conditions of laser power being 4 200 watts，scanning speed being 300 mm／min and powder feeding velocity being 1 8 s／min etc．The coating had a higher hardness value of HV780 than that of the SUbstrate material，but there existed a hardness knee point between the coating and the substrate．The laser cladding coating did not appear cracks under the static load of 453 kN．The organsof the Fe -based coating weremainly composed of C-Fe, Cr0. 19Fe0. 7Ni0. 11, NiCrFe and FeCr etc. The martensite structure was formed in the fusion area adjacent to the substrate because of the rapid heating and rapid cooling.

Key words

laser cladding / rail surface / Fe -based alloy / microstructure and property

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YANG Jiao—xi, LIU Hua—dong. Research on the Microstructure and Properties of Laser Cladding Fe—base Alloy on U71 MU Rail Surface[J]. Journal of Railway Engineering Society, 2010, 27(7): 34-37

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