纳米金刚石涂层微铣钻刀具制备新方法及应用基础研究

This Project will develop a novel fabrication method of nanocrystalline diamond (NCD) coated micro-tools, that includes a novel pretreatment and surface enhancemnent method for micro-sized tools, a low-temperature NCD deposition process and a substrate temperature maintaining system. This study will illustrate the effect of the surface cobalt etching and roughening, and the thermal diffusion of cobalt inside the micro-tool on the deterioration of fracture strength and toughness of micro-tools during pretreatment, as well as the effect of the arrangement between filaments and micro-tools, the inlet and outlet positions of the reagent gases, the flux of reactive gases, and the thermostat sample holder on the distribution of temperature, and reagent gas velocity and density over a large-are. Based on abovementioned studies, a layer of continuous, smooth, and defect-free NCD coating, with diamond grain size lower than 30 nm, thickness 0f 400-600 nm, and thickness deviation over the micro-tool surface lower than 50 nm will be deposited on micro-milling and micro-drilling tools with diameter ranging from 0.15–1.0 mm. For the application research, the micro-machining performance of as-fabricated NCD coated micro-tools will be evaluated in micro-drilling of PCB board, micro-milling of EDM graphite electrode and 7075 aluminum, which will give a deep insight into the micro-machining mechanism of NCD coated micro-tools, including its micro-sized interactive behaviors against workpiece, failure mechanism, material removal mechanism, as well as the quantified relationship among the micro-machining performance of NCD coated micro-tools, the characters of NCD coating and the micro-machining parameters. Based on these results, the deposition method of NCD coated micro-tools and the micro-machining parameters will be optimized with aiming at increasing the wear resistance of as-fabricated NCD coated micro-tools by 5 times and reducing the cutting force by 50% comparing with uncoated WC-Co micro-tools, which will significantly promote the successful application of as-fabricated NCD coated micro-tools in machining typical micro-sized parts.

针对Φ0.15–1.0mm微铣钻刀具开发纳米金刚石涂层微铣钻刀具制备新方法，包括微小尺寸基体预处理及表面强化技术，低温环境下纳米金刚石涂层沉积工艺以及基体独立恒温系统的研制，揭示刀具基体表面粗化、钴刻蚀、基体内部钴元素在高温环境下的热扩散等因素对其断裂强度及韧性的损伤机理，以及大面积沉积环境中微铣钻刀具基体表面温度场及流体密度场分布规律与热丝及基体的相对位置、反应气体进出口及流速、基体独立恒温装置等因素之间的关系，从而在微铣钻刀具表面沉积获得表面光滑、连续、无缺陷，晶粒尺寸小于30nm、厚度400-600nm且基体表面不同位置的薄膜厚度偏差不超过50nm的高质量纳米金刚石涂层。通过PCB板微钻削、EDM石墨电极与铝合金微铣削实验考察纳米金刚石涂层微铣钻刀具的切削性能，揭示微观尺寸下刀具与工件材料之间的作用机制、材料去除机理及失效机理，以及它们与纳米金刚石涂层性能、微切削工况三者之间的定量关系，从而对纳米金刚石涂层微铣钻刀具制备方法进行进一步优化，最终达到提高刀具耐磨性5倍以及降低切削力50%以上的目标，为实现纳米金刚石涂层微铣钻刀具在典型微细零件加工中的成功应用及产业化奠定基础。

本项目针对金刚石涂层在微铣钻刀具表面应用的技术难题，通过优化传统酸碱刻蚀预处理工艺，将微铣钻刀具预处理后的断裂强度损伤从43.7%降低到7.23%。提出了基于激光热烧蚀技术的硬质合金表面钴刻蚀处理方法，通过优化设计激光脉冲的搭接方式与搭接率，在钴含量6%的硬质合金表面形成的贫钴区域钴含量可达0.5%以下，可对微细刀具复杂表面进行高精度、高可控的钴刻蚀过程，进而实现对基体强度无损伤的金刚石涂层预处理。基于大面积微铣钻刀具沉积区域温度场分布规律的研究成果，构建了不等间距的热丝排布方式，开发了生长区域温度在线监测系统以及基于温度场均匀性的沉积工艺控制策略，从而实现了金刚石涂层沉积过程中单一沉积区域的温度波动幅值小于\±5℃，全部沉积区域偏差不超过10 ℃的生长环境温度控制目标。提出了一种在高碳氢比与富氧环境下沉积低温纳米金刚石涂层的新方法，在450℃低温条件下沉积获得了硼掺杂纳米金刚石涂层。基于新型基体预处理方法、低温沉积纳米金刚石涂层方法以及优化后的沉积参数制备的纳米金刚石涂层微铣刀和微钻头表面光滑、连续、无缺陷，在切削7075铝合金、石墨以及钻削PCB板的过程中均表现出优异的性能，刀具寿命比未涂层刀具提高5倍以上，切削力降低50%以上，加工表面完整性好。对切削过程中的金刚石涂层微铣钻刀具与工件材料的作用机制、材料去除机理以及刀具失效形式进行了深入研究，揭示了涂层类型、厚度等因素与加工表面完整性之间的关系。结果显示，随着微铣刀表面的金刚石涂层厚度增加，涂层残余压应力线性减小，抗冲击性能降低，膜-基附着强度显著降低。目前，本项目开发的纳米金刚石涂层微细刀具制备技术与HFCVD沉积装备已应用于世界领先的刀具供应商春保-森拉天时集团，用于制造面向石墨等硬脆性材料加工的金刚石涂层微细刀具。本项目的研究成果有望在有色金属、航空航天用碳纤维复合材料以及硬脆性材料加工用金刚石涂层刀具制备领域中获得广泛的应用。