硬质合金刀具微尺度刃口涂层技术与创成方法研究

The hard and brittle material is apt for ductile transition in microscale edge of diamond tool cutting. However it is difficult to sharpen the cutting edge because of high hardness and wear resistance of diamond tool. It is easy to sharpen the cutting edge of the cemented carbide tool which is lower wear and life than the diamond tool. In this project a new preparation method of cutting tool is studied to sharpen the cutting edge, improve the wear resistance and lengthen tool life. At first, the cemented carbide tool is sharpened for microscale edge by precision grinding and lapping. Then, the diamond like carbon (DLC) film is deposited on the substrates of the cemented carbide tool. A new cemented carbide cutting tool coated with DLC film is fabricated. In experiment, the new tool cutting performance is researched in cutting the silicon crystal. In the project, the brittle-ductile transition mechanism of the cemented carbide is studied in grinding and mechanical lapping. The acoustic emission sensor is utilized to receive the stress wave signals and assess the surface integrity of the cutting edge. The stress wave signals are generated by the material cracks, plastic deformation and the rapid release of strain energy in grinding and mechanical lapping. It is very important to research the microscale cutting edge of the cemented carbide in grinding and mechanical lapping. It is an eventful technology of DLC film deposition process. A new cemented carbide tool fabrication with DLC film preparation is established. The cutting performance is studied for DLC film coated cemented carbide tool in texturing silicon crystal process. By this project, the new theory and technology are provided for silicon crystal surface texturing of photovoltaic solar cells in high-precision machining.

微尺度刃口金刚石刀具易于实现硬脆材料延性域加工。金刚石刀具硬度高、耐磨损，但切削刃的刃口难于刃磨到微尺度，而硬质合金刀具切削刃的刃口易于刃磨到微尺度，但与金刚石刀具相比易磨损，寿命低。本项目提出先刃磨硬质合金刀具获得微尺度刃口，进而在硬质合金刀具刃口衬底沉积类金刚石薄膜涂层，研制具有微尺度刃口、较强抗磨损能力和较高刀具寿命的类金刚石薄膜涂层硬质合金刀具，并探讨其加工硅晶体的切削性能。本项目通过研究硬质合金刀具衬底的脆-延转变低损伤机械刃磨机理，利用声发射传感器接收并分析因材料裂纹、塑性变形等引起应变能快速释放而产生的应力波，评定刀具刃口表面完整性；研究刀具微尺度刃口的机械刃磨工艺和类金刚石薄膜涂层的沉积工艺，建立类金刚石薄膜涂层硬质合金刀具的制备技术；探讨类金刚石薄膜涂层硬质合金刀具在硅晶体表面制绒中的切削性能，为用于光伏太阳能电池的硅晶体表面制绒高效精密加工提供基础理论和工艺技术。

刀具表面涂层的目的是增效和延寿。本项目提出在硬质合金刀具表面沉积类金刚石涂层，研制具有较强抗磨损能力和较高使用寿命的类金刚石涂层硬质合金刀具，并研究了其加工硅晶体的切削性能。结果表明：类金刚石涂层与硬质合金基体有较好的结合强度，类金刚石涂层可以延长硬质合金刀具的寿命，提高使役性能。建立了等离子清洗硬质合金衬底的预处理方法，利用等离子辅助磁控溅射技术在硬质合金刀具表面制备了5种含有纯金属过渡层的类金刚石涂层。具有Cu和Ag过渡层的类金刚石涂层含有较高含量的sp3键。具有Ti和W过渡层的类金刚石涂层硬度较高。具有W过渡层的类金刚石涂层的膜-基结合力最好。具有Ti和W过渡层的类金刚石涂层耐磨性较好。基于硬脆材料延性域加工理论，建立了延性域微切削的临界进给速度模型和切屑分离准则。基于流体动力学理论建立了磨削液在气障层内的流动轨迹模型，研究了不同磨削工况下磨削气障层对磨削液进入磨削弧区的影响规律，结合喷嘴截面形状、喷嘴位置和喷射角度，建立了磨削液有效供给的方法。基于传热学理论，建立了磨削硬质合金过程中磨削弧区磨削液的对流换热系数计算模型和磨削温度预测模型。通过实验测试得到的温度与理论计算的误差在22%以下。在KERN五轴超精密加工中心分别采用类金刚石涂层和未涂层的硬质合金刀具进行硅晶体加工，发现未涂层的硬质合金刀具磨损非常迅速，加工距离短，加工后的硅晶体有微裂纹和微缺陷，而类金刚石涂层硬质合金刀具可以有效增加加工距离，提高硅晶体表面的加工质量。类金刚石涂层硬质合金刀具是一种很有市场潜力的刀具，具有广阔的应用前景。