Pacella Manuela, Saremi-Yarahmadi Sina, Lamberti Luciano
Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
Department of Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
Materials (Basel). 2021 Jan 21;14(3):516. doi: 10.3390/ma14030516.
Polycrystalline cubic boron nitride (PcBN) are super-hard materials with high hardness and excellent abrasive resistance, widely used in cutting tools for precision machining of automotive and aerospace parts; however, their brittle properties make them prone to premature failure. Coatings are often applied to PcBN to extend their range of applicability and durability. Conventional coating methods are limited to the thickness range of a few hundred nanometres, poor adhesion to the substrate, and limited stability under ambient conditions. To further the properties of PcBN composites, in this paper, we explore the use of ultrasonic bonding to apply thick coatings (30-80 μm) on PcBN cutting tools. For the first time, a multi-walled carbon nanotube (MWCNT) powder is preplaced on a PcBN substrate to allow an unconventional coating technique to take place. The effects of ultrasonic bonding parameters on the change of mechanical properties of the coated tools are investigated through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-hardness analyses, and white light interferometry. The structure of the carbon nanotubes is investigated through transmission electron microscopy (pre coating) and cross-section of the bonded MWCNTs is studied via focused ion beam milling and SEM to evaluate the bonding between the multi-walled nanotubes. Optimum processing windows (i.e., bonding speed, energy, and pressure) are discovered for coating MWCNTs on PcBN. Focus ion beam milling analyses revealed a relationship between consolidation parameters and porosity of MW(pCNT) bonds. The proposed method paves the way for the novel design of functional coatings with attunable properties (i.e., thickness and hardness) and therefore improved productivity in the machining of aerospace and automotive parts.
多晶立方氮化硼（PcBN）是具有高硬度和优异耐磨性的超硬材料，广泛应用于汽车和航空航天零件精密加工的切削刀具；然而，其脆性使其容易过早失效。通常会在PcBN上涂覆涂层以扩大其适用范围和耐久性。传统的涂层方法限于几百纳米的厚度范围，与基体的附着力差，并且在环境条件下稳定性有限。为了进一步改善PcBN复合材料的性能，在本文中，我们探索使用超声键合在PcBN切削刀具上施加厚涂层（30 - 80μm）。首次将多壁碳纳米管（MWCNT）粉末预先放置在PcBN基体上，以实现一种非常规的涂层技术。通过扫描电子显微镜（SEM）、能量色散X射线光谱（EDX）、显微硬度分析和白光干涉测量法研究了超声键合参数对涂层刀具力学性能变化的影响。通过透射电子显微镜（预涂层）研究碳纳米管的结构，并通过聚焦离子束铣削和SEM研究键合的多壁碳纳米管的横截面，以评估多壁纳米管之间的键合。发现了在PcBN上涂覆MWCNT的最佳加工窗口（即键合速度、能量和压力）。聚焦离子束铣削分析揭示了固结参数与MW（pCNT）键孔隙率之间的关系。所提出的方法为具有可调节性能（即厚度和硬度）的功能涂层的新颖设计铺平了道路，从而提高了航空航天和汽车零件加工的生产率。
