Effect of Sn modification on microstructure and mechanical properties of graphite/Cu composites
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摘要: 石墨/Cu自润滑复合材料具有良好的摩擦学性能和耐腐蚀性能,在高速铁路领域具有广阔的应用前景。传统石墨/Cu自润滑复合材料中由于石墨与基体不润湿,复合材料界面结合强度低,在材料承受载荷时容易造成石墨相的剥离、脱落,导致复合材料在高载荷服役条件下性能较差。采用化学镀覆工艺在石墨表面镀覆软金属Sn元素调控石墨/Cu复合材料界面,既能够改善复合材料材料组织,又改善了复合材料的力学性能,使复合材料满足服役条件。结果表明:通过石墨镀Sn调控技术,Sn调控石墨/Cu复合材料的组织并无新相生成,复合材料界面处发生强烈的原子互扩散,界面由机械结合变成扩散结合。Sn调控石墨/Cu复合材料的力学性能有显著提高,其中硬度平均提高了80.43%,抗弯强度平均提高了246.74%;当石墨含量为6wt%时,Sn调控石墨/Cu复合材料的硬度提高至(83.61±4.33) HV,抗弯强度提高至(410.41±20.52) MPa,适应并满足复合材料在未来愈加严酷工况环境下的服役需求。Abstract: The graphite/Cu composites have excellent tribological properties and corrosion resistance so which show a broad application prospect in the field of high-speed railway. Due to the non-wetting of graphite with Cu and the low interfacial bonding strength of graphite/Cu composites, the graphite easily peels off under the high load and it could result in the poor performance of the composites. The interface of graphite/Cu composite could be modified by the surface treatment of the graphite with Sn element, which could not only improve the interfacial bonding but also improve the mechanical properties, so that the composites could meet the service conditions. The results show that there is no new phase formation in the microstructure of Sn coated graphite/Cu composites by the interfacial modification. A strong interdiffusion occurs at the interface of the Sn coated graphite/Cu composites and the interfacial bonding changes from mechanical bonding to diffusion bonding. The mechanical properties of the Sn coated graphite/Cu composites are significantly improved. The hardness and flexural strength increase 80.43% and 246.74%, respectively. When the graphite content is 6wt%, the hardness is (83.61±4.33) HV, and the bending strength is (410.41±20.52) MPa, which could meet the service requirements in the future.
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表 1 镀Sn石墨的化学镀液成分
Table 1. Composition of chemical plating solution of Sn coated graphite
SnCl2/(g·L−1) HCl/(mL·L−1) Thiourea/(g·L−1) PEG-6000/(g·L−1) Hydroquinone/(g·L−1) NaH2PO2/(g·L−1) Content 30.0 45.0 100.0 2.0 3.5 80.0 Note: PEG-6000—Polyethylene glycol-6000. 表 2 Sn调控石墨/Cu复合材料样品编号及成分
Table 2. Sample number and chemical composition of Sn coated graphite/Cu composites
No. Sn coated
graphite/wt%Ni/
wt%Cu/
wt%Sn coated graphite/Cu-1 1 8 Balance Sn coated graphite/Cu-2 2 Sn coated graphite/Cu-3 3 Sn coated graphite/Cu-4 4 Sn coated graphite/Cu-5 5 Sn coated graphite/Cu-6 6 表 3 镀Sn石墨表面EDS点扫描结果
Table 3. EDS point results of Sn coated graphite
Point C element Sn element O element Mass fraction/wt% Atom fraction/at% Mass fraction/wt% Atom fraction/at% Mass fraction/wt% Atom fraction/at% 1 13.8 37.7 64.4 17.8 21.8 44.5 2 13.8 38.7 65.8 42.8 20.4 18.5 3 14.2 55.5 81.7 32.3 4.1 12.2 4 12.8 40.6 72.1 36.2 15.1 23.3 表 4 6wt%石墨含量的镀Cu、Ni、Ti、Ag、Sn调控石墨/Cu复合材料力学性能对比
Table 4. Comparison of mechanical properties of Cu, Ni, Ti, Ag, Sn modified graphite/Cu composites with 6wt% content of graphite
Sample Hardness (HV) Flexural strength/MPa Unmodified 38.93 95.27 Cu modified 41.85 125.42 Ni modified 45.25 137.14 Ti modified 50.23 190.54 Ag modified 59.25 275.19 Sn modified 83.61 410.41 -
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