Laser implantation of press hardening tools to influence the tribological and thermal properties for the process application

汽车工业的主要发展目标是提高乘员安全性、降低油耗和实现排放法规。因此，热冲压被认为是制造高强度和轻量化白车身部件的一种合适的、资源高效的工艺。然而，由于高热机械工具应力和缺乏润滑剂，生产受到摩擦和磨损的限制。本研究项目的总体目标是通过激光注入过程对刀具表面进行改性，以影响接触区的热、机械和摩擦学相互作用。在第一个项目阶段，通过数值模型确定了摩擦学高应力工具区域以及对种植体几何形状的要求。此外，还确定了合适的硬质陶瓷颗粒，并分析了它们与不同激光参数的相互作用。摩擦学实验表明，由于接触面积的限制和刀具与工件之间化学亲和力的降低，激光注入刀具具有较高的耐磨性和较低的摩擦力。通过修改与行业相关的刀具几何形状，最终证明了提高了零件质量和改善了成形行为。然而，基于数值结果，最大的刀具载荷位于几何复杂区域，由于缺乏植入策略和刀具与工件之间的未知因果关系而无法进行激光注入。因此，预计构建这些高应力工具区将显著改善摩擦学行为。在第二个项目阶段，必须启动关于不同刀具应力的进一步研究，以确定表面特性、摩擦和磨损行为之间的相互作用。在这种情况下，将为特定的载荷情况创建由硬质相成分和量身定制的结构模式制成的合适的植入物。之后，它们将在与工业相关的实验中进行测试，以验证其有效性。这种方法提供了关于硬质陶瓷颗粒之间的相互作用和高应力工具区域中植入物的布置的更深层次的理解。

Major development goals of the automotive industry are to increase the passenger safety as well as to reduce the fuel consumption and to achieve emission regulations. Hence, hot stamping has been established as a suitable and resource efficient process to manufacture high-strength and lightweight body-in-white components. However, the production is limited by friction and wear due to high thermo-mechanical tool stresses and the lack of lubricants. The overall aim of this research project is to modify the tool surface by using a laser implantation process in order to influence the thermal, mechanical and tribological interactions in the contact zones. Within the first project phase, tribological highly stressed tool areas as well as requirements for the implant geometry were identified by means of numerical models. Furthermore, suitable hard ceramic particles were determined and their interactions with different laser parameters were analyzed. Tribological experiments have shown that laser-implanted tools exhibit a high wear resistance and decreasing friction forces due to the limitation of the contact area and the reduced chemical affinity between tool and workpiece. By modifying an industry-related tool geometry, it was finally proven that an increased part quality and an improved forming behavior was achieved. However, based on the numerical results, maximum tool loads were located in geometrical complex areas which could not be laser-implanted due to the lack of implantation strategies and the unknown cause-effect relations between the tool and the workpiece. Thus, it is expected that structuring these highly stressed tool areas will significantly improve the tribological behavior. In a second project phase, further investigations with regard to varying tool stresses must be initiated in order to identify the interactions between surface properties, friction and wear behavior. In this context, suitable implants made out of hard phase compositions and tailored structuring patterns will be created for specific load cases. Afterwards, they will be tested in industrially relevant experiments to verify their effectiveness. This approach provides a deeper understanding regarding the interactions between hard ceramic particles and the arrangement of the implants in highly stressed tool areas.