High speed cutting of difficult-to-machine materials with cutting tools coated by Ti-B-C thermally stable films

我们试图通过涂覆钛硼碳（Ti-B-C）薄膜来提高刀具对钛合金（Ti-6A1-4V）的切削性能，钛合金是最难切削的材料之一。以碳化硼（B_4C）为靶材和钛为靶材，采用直流磁控溅射法制备了Ti-B-C薄膜。首先，在硅衬底上进行沉积实验，优化Ti-B-C涂层条件。在沉积过程中，Ti的靶功率为0 ~ 200W， CH_4气体流量为0 ~ 80 sccm，以了解膜中钛和碳的含量对涂层的纳米压痕硬度、摩擦性能和粘接强度的影响。在涂层过程中提高钛的靶功率可以有效地提高薄膜与基体的结合强度。由于CH4的引入，膜的摩擦系数大大降低。此外，这些膜具有良好的耐磨性。在优化的涂层条件下，在碳化钨刀具上制备了Ti-B-C薄膜，并用涂层刀具对钛合金进行了车削试验。Ti-B-C涂层改善了对钛合金的切削性能。Ti-B-C涂层降低了刀具前刀面的磨损。与未涂覆刀具形成的切屑相比，在车削试验期间产生的切屑也被平滑。Ti-B-C涂层在干式切削中也能改善工件表面粗糙度。

We attempt to improve the performance of cutting tools against titanium alloy (Ti-6A1-4V), which is one of the difficult-to-cut materials, by coating of titanium-boron-carbon (Ti-B-C) thin films. We have been prepared the Ti-B-C thin films by DC magnetron sputtering using boron carbide (B_4C) target and titanium target. At first, the deposition experiments were performed with silicon substrates for optimizing the Ti-B-C coating condition. The target power for Ti was varied from O to 200W and CH_4 gas flow rate from 0 to 80 sccm in the deposition process to understand the influences of titanium and carbon contents in the films on the nano-indentation hardness, the frictional properties and the adhesive strength of coatings. Increase of the target power for titanium in the coating process was effective for increasing the adhesive strength of the films onto the substrates. As CH4 introduction in the coating process, the friction coefficient of the films was drastically decreased. Moreover, those films obtained good wear resistant. At the optimized coating condition, the Ti-B-C films were produced on tungsten carbide cutting tools and turning tests were carried out against titanium alloy with the coated tools. The Ti-B-C coating provided improvements in cutting performance against titanium alloys. Tool wear on rake face was decreased by Ti-B-C coating. Chip produced during the turning tests was also smoothed as compared to that formed by the uncoated tool. Surface roughness of workpieces was improved by Ti-B-C coating even in dry cutting.