Relationships between tribological properties of Ti-6Al-4V and the machining behaviour of the same alloy drilled by a WC-Co cutting tool using minimum quantity lubrication (MQL) were studied. The tribological behaviour of Ti-6Al-4V sliding against WC-Co was evaluated by determining the changes in the coefficient of friction (COF) using cutting fluids employed in MQL and flooded drilling tests. When pin-on-disk tests were carried out under the boundary lubricated condition, the MQL fluid (MQLF) provided a low COF of 0.16 at 25 ℃ and 0.24 at 250 ℃. The observed low COFs were attributed to formation of a tribolayer on the WC-Co counterfaces. A high COF of 0.45 observed at 300 ℃ indicated that the tribolayer was no longer stable. Application of conventional water-based cutting fluid (CF) also resulted in a low COF of 0.26 at 25 ℃ but the COF rose to 0.32 at 100 ℃. During drilling tests, MQLF was supplied at a rate of 80 ml/h using an external MQL system. The average drilling torque was reduced by 35% compared to CF as a result of the formation of tribolayer on the cutting edge of the tool as well as on the drilled hole surfaces, as the cutting temperature remained <250 ℃. According to Raman and X-ray photoelectron spectroscopy (XPS) analyses, the tribolayer on the drilled hole surface was formed as a result of degradation of additives in the MQL. The presence of phosphate- and sulfate-based anti-wear components in the tribolayer proved to be beneficial in preventing metal-metal contacts during drilling and provided a low COF. The low COF between tool-workpiece contact resulted in a low and uniform torque response throughout the drilling cycles and prevention of built-up edge (BUE) formation, leading to an improved surface finish.

中文翻译：

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研究摩擦层形成在使用最少量润滑提高 Ti-6Al-4V 钻井性能中的作用

研究了 Ti-6Al-4V 的摩擦学性能与使用最小量润滑 (MQL) 的 WC-Co 刀具钻削的相同合金的加工行为之间的关系。Ti-6Al-4V 与 WC-Co 滑动的摩擦学行为是通过使用 MQL 和淹没钻井测试中使用的切削液确定摩擦系数 (COF) 的变化来评估的。在边界润滑条件下进行销盘式测试时，MQL 流体 (MQLF) 在 25 ℃ 和 250 ℃ 下提供 0.16 和 0.24 的低 COF。观察到的低 COF 归因于在 WC-Co 反面上形成了摩擦层。在 300 ℃下观察到的 0.45 的高 COF 表明摩擦层不再稳定。应用传统的水基切削液 (CF) 也导致 25 ℃ 时的 COF 低为 0.26，但 COF 升至 0。32 在 100 ℃。在钻井测试期间，MQLF 使用外部 MQL 系统以 80 毫升/小时的速度供应。由于在刀具切削刃和钻孔表面形成摩擦层，切削温度保持 <250 ℃，平均钻孔扭矩比 CF 降低了 35%。根据拉曼和 X 射线光电子能谱 (XPS) 分析，钻孔表面的摩擦层是 MQL 中添加剂降解的结果。事实证明，摩擦层中磷酸盐和硫酸盐基抗磨成分的存在有利于防止钻井过程中金属与金属的接触，并提供低 COF。工具与工件接触之间的低 COF 导致整个钻孔周期的扭矩响应低且均匀，并防止积屑瘤 (BUE) 形成，