Friction and Wear Mechanisms of Nanocrystalline Nickel in Ambient and Inert Atmospheres
Friction and Wear Mechanisms of Nanocrystalline Nickel in Ambient and Inert Atmospheres
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DOI：
10.1007/s11661-007-9157-y
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
M. Shafiei;A. Alpas
中科院分区：
文献类型：
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作者：
M. Shafiei;A. Alpas
研究了测试环境对晶粒尺寸为15±3nm、硬度为519±11Hv的纳米晶(nc)Ni摩擦磨损行为的影响，并与晶粒尺寸为20±5μm、硬度为122±5Hv的微晶(mc)Ni进行了比较。摩擦系数 (COF) 和磨损率是在周围空气和氩气环境中使用销盘摩擦仪测量的，该摩擦仪在 2 N 的恒定负载和 0.1 m/s 的滑动速度下相对于球形 Al2O3 配合面 (H= 1,900 ± 40 Hv) 运行。配合面施加的初始接触压力 (1.56 GPa) 足够高，足以在 mc Ni 的接触表面上引起塑性变形，但不会在 nc Ni 的表面上引起塑性变形，前八个周期的初始磨损率几乎小两个数量级 (Wi(mc) = 7.88 × 10−3mm3/m，Wi(nc) = 0.16 × 10−3mm3/m）。在氩气中测试时，两个样品都表现出较高的磨损率，但 nc Ni 的初始磨损率要低得多（即，在前八个循环中，WiAr(mc) = 9.97 × 10−3mm3/m 和 WiAr(nc)= 0.22 × 10−3mm3/m）。在两种气氛中，COF 曲线均迅速增加，并在下降至稳态值之前达到峰值。 nc Ni 的 COF 峰值小于 mc Ni 在空气中（COFp(mc) = 0.71，COFp(nc) = 0.58）以及氩气中（COFpAr(mc) = 1.14，COFpAr(nc) = 0.77）的峰值。两个样品在空气中比在氩气中更早达到稳态磨损条件。与 mc Ni 相比，nc Ni 在空气（Wss(mc)=0.13×10−3mm3/m，和 Wss(nc)=0.03×10−3mm3/m）和氩气（WssAr(mc)=0.18×10−3mm3/m，和WssAr(nc) = 0.07 × 10−3mm3/m) 环境。 NC Ni 的磨损轨迹因配合面的刮擦作用而不断加宽。在环境大气中，氧化碎片颗粒聚集，在数控镍磨损轨迹的顶部形成致密的保护摩擦层。在氩气氛中，摩擦层是不连续的，覆盖了大约一半的磨损轨迹，并且由于氧化物含量较少而具有较低的硬度，从而导致较高的稳态磨损率和COF值（COFss（nc）= 0.41和COFssAr（nc）= 0.58）。
The role of testing environment on the friction and wear behavior of nanocrystalline (nc) Ni with a grain size of 15 ± 3 nm and a hardness of 519 ± 11 Hv has been studied in comparison with microcrystalline (mc) Ni with a grain size of 20 ± 5μm and a hardness of 122 ± 5 Hv. Coefficients of friction (COFs) and wear rates were measured in ambient air and argon environments using a pin-on-disc tribometer operated at a constant load of 2 N and a sliding speed of 0.1 m/s against a spherical Al2O3counterface (H= 1,900 ± 40 Hv). The initial contact pressure exerted by the counterface (1.56 GPa) was sufficiently high to induce plastic deformation on the contact surface of the mc Ni but not on the surface of the nc Ni for which the initial wear rate in the first eight cycles was almost two orders of magnitude smaller (Wi(mc) = 7.88 × 10−3mm3/m, andWi(nc) = 0.16 × 10−3mm3/m). Both samples showed higher wear rates when tested in argon, but again the initial wear rate of the nc Ni was much lower (i.e., during the first eight cycles,WiAr(mc) = 9.97 × 10−3mm3/m andWiAr(nc)= 0.22 × 10−3mm3/m). In both atmospheres, the COF curves increased rapidly and exhibited a peak before they decreased to a steady-state value. The peak value of the COF for the nc Ni was less than that of the mc Ni in air (COFp(mc) = 0.71, and COFp(nc) = 0.58) as well as in argon (COFpAr(mc) = 1.14, and COFpAr(nc) = 0.77). Steady-state wear conditions in both samples were reached earlier in air than in argon. Compared to the mc Ni, the nc Ni maintained lower steady-state wear rates in both air (Wss(mc) = 0.13 × 10−3mm3/m, andWss(nc) = 0.03 × 10−3mm3/m) and argon (WssAr(mc) = 0.18 × 10−3mm3/m, andWssAr(nc) = 0.07 × 10−3mm3/m) environments. The wear track of the nc Ni was continuously widened by the scratching action of the counterface. In the ambient atmosphere, oxidized debris particles became agglomerated, forming a compacted protective tribolayer on the top of the wear track of the nc Ni. In the argon atmosphere, the tribolayers were discontinuous, covering about half of the wear tracks, and had lower hardness because of their lesser oxide content, resulting in higher steady-state wear rates and COF values (COFss(nc) = 0.41, and COFssAr(nc) = 0.58).