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

由于生态、经济和立法的原因，在全前挤压（VVFP）过程中需要排除润滑剂。这导致摩擦增加，从而增加了摩擦系统的磨损。因此，摩擦系统必须通过工件和刀具的修改来适应。这可以通过工件表面的结构和工具的涂层来实现。在项目的第一阶段，研究了（Cr,Al）N + XS2 （X = Mo， W）体系中结构化工件表面和自润滑刀具涂层对工件与涂层刀具之间摩擦剪切应力的影响。在第二个项目阶段，结果被转移到单模干式VVFP工艺。然而，将VVFP的发现转移到多模VVFP是不可能的。这是由于与单模具工艺相比，多模具VVFP中的摩擦学和机械负荷显着增加且相当不同。在多模干式VVFP中涉及的另一个挑战是沿着工具纵轴变化的摩擦学边界条件。此外，由于双模刀具的纵向变化的摩擦学条件，目前尚不清楚，是否和在多大程度上涂层一个不分段的，单块刀具的现有方法是足够的。因此，第三个项目阶段的总体目标是开发干式多模VVFP的解释性模型，该模型描述了摩擦系统的磨损行为，该摩擦系统由具有结构表面的工件和具有自润滑涂层的工具组成，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）通过实验和模拟调查，在考虑选定的表面完整性的情况下，对多模干式VVFP的摩擦学边界条件以及刀具磨损进行研究。在表面工程研究所（IOT），将研究现有的自润滑硬涂层（Cr,Al）N+XS2 (X = Mo或W)，采用dcMS/HPPMS（直流/大功率脉冲磁控溅射）混合技术沉积，根据刀具纵向轴的不同摩擦学边界条件进行调整。在这里，将研究两种涂层概念，即非分段、单块刀具的涂层和轴向分段刀具的涂层。随后将通过实地试验确定更经济的概念。在WZL和IOT之间的密切合作下，将有可能首次在多模具全正向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.