Analysis of discharge-dependent surface integrity of cemented carbide forming dies machined by sinking EDM and its influence on the tribological characteristics and the resulting fatigue behavior

由于硬质合金具有良好的耐磨性和较高的抗压强度，在金属成形中作为工具材料具有日益增长的潜力。它们的特点是硬度比钢高，同时抗弯强度比陶瓷高。在这种情况下，弯曲强度是工具设计的基本材料参数，因为弯曲应力通常是关键的失效原因。然而，硬金属作为金属成形中活性元素的工具材料的进一步普及与高材料，特别是高加工成本相矛盾。电火花加工与材料的机械性能无关，是硬质合金成形模具加工的一项关键技术。然而，加工硬质合金刀具的韧性往往低于预期。造成这种情况的一个原因是缺乏使工具表面适应需求概要文件的过程知识。另一方面，现有技术和先前工作的结果表明，通过在整个工艺链中进行适当的工艺设计，可以具体而显著地提高最终部件的强度。该项目的目标涉及对放电相关的电火花加工（电火花加工）表面完整性对硬质合金材料制成部件的摩擦学和机械行为的影响进行科学和结构化的分析。在之前的研究阶段，提出了几个问题，应该在随后的研究期间回答。应采用全因子实验设计来创建一个模型，该模型可以从物理上解释表面完整性与过程能量的依赖关系。该模型的一般适用性应在第二台机床上进行验证。摩擦学材料行为的描述模型显示出非线性，需要在额外的实验中进行研究。另一个尚未被科学地描述的影响是在硬质合金加工时发生的几何形状偏差。应该通过改变电极材料和加工参数来收集引起这种影响的信息。为了表明电火花加工对硬质合金加工的适用性，需要对后续的几个处理步骤进行检验。这些发现将用于设计和制造多个硬质合金冷成形模具，并将在实际条件下进行测试。最后，应该从两个研究时期的所有发现中创建一个模型。这应该用于为用户、机床和材料制造商提供建议。

Cemented carbides have a growing potential as a tool material in metal forming because of their great resistance to wear and high compressive strength. They are characterized by an increased hardness compared to steels and simultaneously increased bending strength compared to ceramics. The flexural strength in this context is an essential material parameter for tool design, as bending stresses are often critical failure reasons. The further spread of hard metals as a tool material for active elements in metal forming are however conflicted by high material- and particularly high processing costs. Due to its independence from mechanical material properties, Electrical Discharge Machining (EDM) is a key technology for the machining of cemented carbide forming dies. However, machined carbide tools often show a toughness that remains below expectations. One reason for this is the lack of process knowledge to adapt the tool surfaces specifically to the requirement profile. On the other hand, the results presented in the state of the art and the previous work show that the final component strength can be specifically and significantly increased through adequate process design within the entire process chain. The objective of the project involves the scientific and structured analysis of the influence of discharge-dependent surface integrity of EDM (Sinking EDM) on the resulting tribological and mechanical behaviour of components made from cemented carbide materials.In the previous research phase, several issues were raised and should be answered over the course of this subsequent research period. A full factorial experimental design should be used to create a model that can physically explain the dependence of surface integrity from the process energy. The general applicability of the model should be verified on a second machine tool. The description model of the tribological material behaviour has shown non-linearities that need to be investigated during additional experiments. Another effect that has not yet been scientifically described, is the geometrical shape deviation occurring upon machining of cemented carbide. Information on the cause of this effect should be gathered by varying the electrode material and the machining parameters. In order to show the applicability of EDM for the machining of cemented carbides, several subsequent treatment steps should be examined. These findings should be used to design and manufacture multiple cold forming dies from cemented carbide, which are going to be tested under realistic conditions. Finally a model should be created from all the findings made in both research periods. This should be used to derive recommendations for users, machine tool and material manufacturers.