Diamond-Silicon carbide-coatings for cutting tools

硬质合金刀具（WC：Co）上的薄金刚石涂层由于其高硬度、耐磨性和对有色金属的低附着力，特别适合于加工增强的轻金属、塑料和石墨。然而，碳化钨中的钴粘合剂会对涂层附着力产生负面影响。因此，通常通过化学蚀刻程序对基底进行预处理，该化学蚀刻程序从工具基底的边界区域去除钴粘合剂。这种预处理可能对工具的机械完整性具有不利影响，并且非常耗时和昂贵。获得高涂层附着力并同时减少预处理工作和对硬质合金工具的机械性能的负面影响的有希望的方法是将金属-硬质合金中间层施加到基底。该中间层用作扩散阻挡层，从而保护金刚石膜免受钴粘结相的影响。夹层和金刚石之间的高粘附力对于该概念是必不可少的。例如，渐变金刚石涂层可以实现这种粘附力，这在本项目中进行了研究。具有高附着力的中间层系统可能允许硬质合金工具刀片涂覆金刚石而不降低稳定性。通过残余应力测量、模型磨损试验和与轻金属AlSi 17 Cu 4 Mg的切削试验，验证了涂层系统的合格性。

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.