Chemical vapor deposition (CVD) diamond thick film, due to its higher hardness and better wear resistance, is a potential competitor of the poly-crystalline diamond (PCD) when used as the brazed tool tip. Besides, compared with the thin diamond coated tool, the diamond thick film brazed tool does not have the risk of catastrophic coating delamination. However, due to the fragile characteristic of the free-standing diamond thick film, the conventional polishing is complicated and inefficient. In this study, a novel CVD-diamond thick film-Si₃N₄ brazed WC-Co (i.e. DB) tool is proposed. The diamond thick film was deposited on the Si₃N₄ substrate by microwave plasma CVD (MPCVD), using the optimized deposition parameters: microwave power = 3.5 kW, reactant pressure = 20 kPa and methane concentration = 10 %. Adopting the sandblasting and nanodiamond seeding pretreatment methods could improve the film surface smoothness and suppress the voids formation on the film-substrate interlayer, which are beneficial for the post polishing process. In addition, Si₃N₄ as the supportive substrate could help to prevent the diamond film breaking from polishing. The polished CVD diamond thick film-Si₃N₄ was laser cut to small tips and then brazed on the WC-Co cutter body. The cutting performance of DB tool was tested in dry turning hypereutectic Al-Si alloy, adopting the PCD and thin diamond coated WC-Co (i.e. DC) tools as comparisons. The cutting results suggest that DB tool outperformed the PCD and DC tools in term of service life and surpassed the DC tool in machining quality. Moreover, the novel tool in this study avoided some typical problems for the conventional diamond tools, such as the coating delamination for thin diamond coated tool and preferred wear of the binder for PCD tool. Noteworthy is that the worn DB tool still presents a rather sharp cutting edge, only some micro-columnar diamond crystals chipped from the flank face.

当化学气相沉积（CVD）金刚石厚膜具有更高的硬度和更好的耐磨性时，当用作钎焊工具头时，是多晶金刚石（PCD）的潜在竞争者。此外，与薄金刚石涂层工具相比，金刚石厚膜钎焊工具不具有灾难性涂层分层的风险。然而，由于自支撑金刚石厚膜的易碎特性，常规抛光复杂且效率低下。在这项研究中，提出了一种新型的CVD金刚石厚膜Si ₃ N ₄钎焊WC-Co（即DB）工具。金刚石厚膜沉积在Si ₃ N _4上使用优化的沉积参数，通过微波等离子体CVD（MPCVD）沉积基材：微波功率= 3.5 kW，反应物压力= 20 kPa，甲烷浓度= 10％。采用喷砂和纳米金刚石籽晶预处理方法可以提高薄膜表面的光滑度，并抑制薄膜-基材中间层上形成空隙，这对后抛光工艺有利。另外，Si ₃ N ₄作为支撑衬底可以帮助防止金刚石膜破裂而被抛光。抛光的CVD金刚石厚膜-Si ₃ N ₄用激光切割成小尖端，然后将其钎焊在WC-Co刀具主体上。DB工具的切削性能在干车削过共晶Al-Si合金中进行了测试，采用PCD和薄金刚石涂层的WC-Co（即DC）工具进行比较。切削结果表明，在使用寿命方面，DB刀具的性能优于PCD和DC刀具，并且加工质量超过了DC刀具。此外，本研究中的新型工具避免了常规金刚石工具的一些典型问题，例如，薄金刚石涂层工具的涂层分层以及PCD工具粘结剂的优选磨损。值得注意的是，磨损的DB工具仍然具有相当锋利的切削刃，只有一些微柱状的钻石晶体从侧面掉落。