Microstructure and wear resistance of Cu ss -toughened Cr 5 Si 3 /CrSi metal silicide alloys
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Wear-resistant Cu-based solid-solution-toughened Cr5Si3/CrSi metal silicide alloy with a microstructure consisting of predominantly the dual-phase primary dendrites with a Cr5Si3 core encapsulated by CrSi phase and a small amount of interdendritic Cu-based solid solution (Cuss) was designed and fabricated by the laser melting process using Cr–Si–Cu elemental powder blends as the precursor materials. The microstructure of the Cuss-toughened Cr5Si3/CrSi metal silicide alloy was characterized by optical microscopy, powder x-ray diffraction, and energy dispersive spectroscopy. The Cuss-toughened silicide alloys have excellent wear resistance and low coefficient of friction under room temperature dry sliding wear test conditions with hardened 0.45% C carbon steel as the sliding–mating counterpart.
I. INTRODUCTION
A metallic material with excellent combination of wear resistance, high thermal conductivity, and low coefficient of friction is highly preferred for most tribological components. M5Si3-type metal silicides such as Mo5Si3, Ti5Si3, W5Si3, Cr5Si3, etc., have attracted considerable attention in recent years as potential high- and/ or ultrahigh-temperature candidate structural materials due to their combinations of high melting point, high elastic modulus, excellent creep and oxidation resistance, and relatively low density and high thermal conductivity.1–8 Many of these M5Si3-based metal silicides have also been preliminarily demonstrated to have outstanding abrasive wear resistance due to their inherent high hardness and adhesive wear resistance and low coefficient of friction due to their strong covalent-dominated atomic bonds and high hardness.6–9 Therefore, many of these M5Si3 silicide-based materials are, from the tribological point of view, expected to be a new class of advanced wear-resistant candidate materials for moving mechanical components working under hostile service environments.8–10 However, all the silicide-based alloys exhibited very poor fracture toughness and tensile ductility at room and intermediate temperatures, which restricted their applications as both structural and tribological
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0174 1122
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 5, May 2005 Downloaded: 18 Mar 2015
components. Fabricating a multiphase intermetallic microstructure by addition of one or more alloying elements especially by introducing a ductile second metallic phase was postulated and demonstrated to be one of the most effective means to enhance the toughness and ductility for most intermetallic alloys.10–17 Copper-based solid solution (hereafter referred to Cuss) is well known for its excellent electrical and thermal conductivity, low coefficient of friction, and excellent ductility.18–22 A multiphase intermetallic alloy with a hard metal silicide, such as Cr5Si3 and CrSi, as the wear resistant reinforcing phase and the ductile Cu-based solid solution (Cuss) as the matrix is expected to be a promising wear
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