The current study evidentially brings out an interesting finding that the chemically inert microcrystalline diamond (MCD) coating having sp³ hybridized C–C network could produce no better result than an uncoated carbide tool in machining aluminium when the latter was provided with the assistance of small quantity lubrication (SQL) technology in an intermittent machining operation like end milling using sunflower oil as cutting fluid. Such an outstanding performance of uncoated tools under SQL condition is thus found to be a potential green solution for milling of aluminium and its alloys where only built-up-edge formation is the primary challenge. Investigation was done on pure aluminium, considering that aluminium alone or Al-rich solid solution phase of any Al-alloy causes the chip to adhere to tool. The SQL, at a flow rate of mere 10 ml/h, when adopted to assist an uncoated carbide tool resulted in superior surface finish (about 75%), compared to that produced by a MCD coated tool under dry environment. An oil film containing long chained molecules of fatty acid got developed at the interface of chip and uncoated tool, enabling an adequate hydrodynamic lift to ensure the arrest of aluminium diffusion in Co-matrix. On the contrary, the rough diamond coating morphology, having projected hard and sharp crystallites of MCD with average height of 1.6 µm resulted in unfavorable deeper groves on finished surface. In addition, the edge radius on the tool, which is otherwise for an effective coating deposition, impaired the smooth shearing action during machining. Interestingly, the same rough morphology of MCD coating served as micro reservoirs of cutting fluid, during SQL application, resulting in a substantial improvement of surface finish, but yet poorer than that obtained under SQL-uncoated tool combination. Two important characteristics of sunflower oil, i.e., its lubrication and wetting ability were investigated and compared with those of a commercially “green” cutting oil before selecting the former as an eligible alternative.

中文翻译：

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葵花籽油对铝的少量润滑辅助立铣

当前的研究显然提出了一个有趣的发现，即具有sp ³的化学惰性微晶金刚石（MCD）涂层如果在间歇性加工操作（如使用葵花籽油作为切削液的立铣刀）中采用小量润滑（SQL）技术的辅助下，在铝的机加工中，混合式C-C网络不会比无涂层的硬质合金刀具产生更好的结果。因此，发现在SQL条件下如此优异的无涂层刀具性能是铝及其合金铣削的潜在绿色解决方案，其中仅堆积边缘成形是主要挑战。考虑到纯铝或任何铝合金的富铝固溶相都会导致切屑粘附在工具上，因此对纯铝进行了研究。当采用SQL时，仅以10 ml / h的流速辅助未涂层的硬质合金刀具，就可以实现卓越的表面光洁度（约75％），与在干燥环境下使用MCD涂层工具生产的产品相比。在切屑和未涂覆的工具的界面处形成了含有脂肪酸长链分子的油膜，从而能够实现足够的流体动力提升，从而确保阻止铝在共基质中的扩散。相反，粗糙的金刚石涂层形态会投射出平均高度为1.6 µm的MCD坚硬而尖锐的微晶，从而导致精加工表面上较深的凹槽变得不利。另外，工具上的边缘半径（否则会导致有效的涂层沉积）削弱了加工过程中的平滑剪切作用。有趣的是，在SQL应用期间，MCD涂层的相同粗糙形态可作为切削液的微储层，从而显着改善了表面光洁度，但仍比未使用SQL的工具组合获得的结果要差。在选择前者为合格替代品之前，研究了葵花籽油的两个重要特征，即其润滑性和润湿性，并将其与商业上“绿色”的切削油进行了比较。