Diamond-Silicon carbide-coatings for cutting tools

碳化钨刀具（WC:Co）上的金刚石薄涂层特别适合加工增强轻金属、塑料和石墨，因为它具有高硬度、耐磨性和对有色金属材料的低附着力。然而，碳化钨的钴结合剂会对涂层的附着力产生不利影响。因此，基材通常通过化学蚀刻程序进行预处理，从工具基材的边界区去除钴粘合剂。这种预处理可能会对工具的机械完整性产生不利影响，并且非常耗时和昂贵。为了获得高涂层附着力，同时减少预处理工作量和对硬质合金刀具力学性能的负面影响，一种有前途的方法是在基体上施加金属-碳化物中间层。该中间层作为扩散屏障，从而保护金刚石膜免受钴结合剂相的侵害。中间层和金刚石之间的高附着力对该概念至关重要。例如，渐进式金刚石涂层可以实现这种粘附性，这是本项目所研究的。一种具有高附着力的层间系统可能允许硬质合金刀具刀片在不降低稳定性的情况下涂覆金刚石。通过残余应力测量、模型磨损试验和轻金属AlSi17Cu4Mg的切削试验，涂层系统是合格的。

Thin diamond coatings on tungsten carbide tools (WC:Co) are particularly suitable for the machining of reinforced light metal, plastics and graphite due to its high hardness, wear resistance and low adhesion to non-ferrous materials. However, the cobalt binder of the tungsten carbides leads to negative effects on the coating adhesion. Therefore, the substrates are usually pre-treated by chemical etching procedures which remove the cobalt binder from the boundary zone of the tool substrate. This pretreatment may have a detrimental effect on the mechanical integrity of the tool and is highly time-consuming and costly. A promising method to gain a high coating adhesion and simultaneously reduce both the pre-treatment effort and the negative influence to the mechanical properties of the carbide tool is to apply a metal-carbide inter layer to the substrate. This interlayer acts as a diffusion barrier and thereby protects the diamond film against the cobalt binder phase. A high adhesion between interlayer and diamond is essential for the concept. Gradual diamond coatings for example could achieve this adhesion, which is investigated in this project. An interlayer system with high adhesion could possibly allow the carbide-tool-inserts to be coated with diamond without reduction of stability. The coating systems are qualified through residual stress measurements, model wear tests and cutting tests with the light metal AlSi17Cu4Mg.