Dry forming of low alloy steels by direct impact extrusion using a self-lubricating tool coating and structured workpieces

由于生态、经济和立法方面的原因，要求在全前向挤压（VVFP）过程中不使用润滑剂。这导致摩擦增加，从而导致摩擦系统中的磨损增加。因此，摩擦系统必须通过修改工件和刀具来适应。这可以通过工件表面的结构化和工具的涂层来实现。在第一个项目阶段，结构化工件表面和自润滑刀具涂层系统（Cr，Al）N + XS 2（X = Mo，W）的工件和涂层刀具之间的摩擦剪切应力的影响进行了研究。在第二个项目阶段，结果被转移到一个单一的模具干燥VVFP过程。然而，不可能将VVFP的发现转移到多管芯VVFP。这是由于与单芯片工艺相比，多芯片VVFP中的摩擦学和机械载荷显著增加且显著不同。多模具干式VVFP中涉及的另一个挑战是沿着工具的纵向轴线沿着变化的摩擦学边界条件。此外，由于双模具工具中的纵向变化的摩擦学条件，仍然不清楚涂覆未分段的单块工具的现有方法是否足够以及在多大程度上足够。因此，第三个项目阶段的总体目标是，开发一个解释性模型的干多模具VVFP，它描述了摩擦系统的磨损行为，包括工件的结构化表面和工具的自润滑涂层作为时间和局部摩擦学边界条件的函数。为此，将在机床和生产工程实验室（WZL）通过实验和模拟研究的方式，在考虑选定表面完整性的情况下，检查多模具干式VVFP中的摩擦学边界条件以及刀具磨损。在表面工程研究所（IOT），调整现有的自润滑硬质涂层（Cr，Al）N+ XS 2（X = Mo或W），沉积使用混合技术dcMS/HPPMS（直流- /高功率脉冲磁控溅射），相对于变化的摩擦学边界条件沿着的纵向轴线的工具将被调查。在这里，两个涂层的概念将被调查，涂层的非分段，单块工具和涂层的轴向分段工具。随后将通过现场试验确定更经济的概念。在WZL和IOT的密切合作下，将首次在多模全正挤压中进行经济的干式金属成形。

Due to the ecological, economic, and legislative reasons, an exclusion of the lubricants during the full forward extrusion (VVFP) is demanding. This leads to an increased friction and thus, to an increased wear in the tribosystem. Therefore, the tribosystem has tobe adapted by a modification of the workpiece and the tool. This is possible by means of a structuring of the workpiece surface and the coating of tools. In the first project phase, the influence of structured workpiece surfaces and self-lubricating tool coatings in system (Cr,Al)N + XS2 (X = Mo, W) on the frictional shear stress between the workpiece and the coated tools was investigated. The results were transferred to a single-die dry VVFP process in the second project phase. However, it is not possible to transfer the findings of the VVFP to the multi-dies VVFP. This is due to the significantly increased and considerably different tribological and mechanical loads in multi-dies VVFP compared to the single-die process. Another challenge involved in the multi-dies dry VVFP is the varying tribological boundary conditions along the longitudinal axis of the tool. Furthermore, due to the longitudinal varying tribological conditions in the two-dies tool, it is still unclear, whether and to what extent the existing approach of coating a not segmented, mono-block tool is sufficient. The overall objective of the third project phase is thus, to develop an explanatory model of the dry multi-dies VVFP, which describes the wear behavior of the tribosystem, consisting of the workpiece with a structured surface and the tool with a self-lubricating coating as a function of the temporal and local tribological boundary conditions. For this purpose, the tribological boundary conditions as well as the tool wear in multidies dry VVFP will be examined under consideration of selected surface integrities by means of experimental and simulativeinvestigations at the Laboratory for Machine Tools and Production Engineering (WZL). At the Institute of Surface Engineering (IOT), an adjustment of the existing self-lubricating hard coating (Cr,Al)N+XS2 (X = Mo or W), deposited using the hybrid technology dcMS/HPPMS (direct current- / High Power Pulsed Magnetron Sputtering), with respect to the varying tribological boundary conditions along the longitudinal axis of the tool will be investigated. Here, two coating concepts will be investigated, the coating of the not segmented, mono-block tool and the coating of the axially segmented tool. The more economic concept will be subsequently identified using the field tests. Within a close cooperation between WZL and IOT, it will be possible for the first time to conduct an economic dry metal forming in a multi-dies full forward extrusion.