Nanostructured Co–Cr–Fe alloy surface layer fabricated by combination of laser clad and friction stir processing
Nanostructured Co–Cr–Fe alloy surface layer fabricated by combination of laser clad and friction stir processing
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激光熔覆与搅拌摩擦加工相结合制备纳米结构Co-Cr-Fe合金表层
DOI：
10.1016/j.surfcoat.2014.08.059
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发表时间：
2014-11
影响因子：
5.4
通讯作者：
Jinglong Li
中科院分区：
文献类型：
--
作者：
Ruidi Li;Tiechui Yuan;Zili Qiu;Kechao Zhou;Jinglong Li
为了将粗大的激光熔覆层组织转变为纳米组织，提高其力学性能，对激光熔覆层进行了搅拌摩擦处理。在激光熔覆Co-Cr-Fe合金的组织中，粗大的脆性碳化物沿晶界析出，并形成网状组织，容易产生微裂纹。经快速凝固处理后，获得了晶粒度为20~100nmN、厚度为30~65nM的纳米结构表面层。粗大的网状碳化物被显著粉碎成纳米尺寸的颗粒，均匀分布在纳米结构的Co基体中。塑料层显示出梯度的颗粒尺寸，从顶部表面的几十纳米到内部的几十微米。在塑性区内发现了大量的形变纳米孪晶，揭示了形变机制。此外，FSP使激光熔覆组织中的微裂纹得以闭合。纳米结构的形成将硬度提高到819Hv，而激光母材的硬度为490Hv。激光熔覆Co合金后，摩擦系数由0.35降至0.1~0.2，磨损性能得到提高。
Friction stir processing (FSP) was carried out on a laser clad Co–Cr–Fe alloy layer in order to transform the coarse laser clad microstructure into nanostructure and improve the mechanical properties. In the microstructure of the laser clad Co–Cr–Fe alloy, coarse brittle carbides precipitated along the grain boundary and formed networks, along which micro-cracks tended to initiate. After FSP, nanostructured surface layers with 20–100 nm grain sizes and 30–65 μm thicknesses were obtained. The coarse network carbides were significantly crushed to nanosize particles uniformly distributed in the nanostructured Co matrix. The plastic layer showed a gradient grain size that ranged from tens of nanometers at the top surface to tens of micrometers at the interior. A large number of the deformation nanotwins were found in the plastic zone which revealed the deformation mechanism. Moreover, FSP enabled the closure of micro-cracks in the laser-clad microstructure. The formation of nanostructures increased the hardness up to 819 Hv, compared with the 490 Hv of the laser parent alloy. The friction coefficients of the laser-clad Co alloy decreased from about 0.35 to 0.1–0.2 after FSP, with enhanced wear performance.
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