Characterization of the application behavior of self-lubricating powder pressing tools

自润滑粉末压制工具的应用行为表征

• 批准号: 403432892
• 负责人: Professor Dr.-Ing. Bernd-Arno Behrens
• 金额: --
• 依托单位: Institut für Umformtechnik und Umformmaschinen (IFUM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/403432892?language=en
• 关键词: Characterization; application; behavior; self; lubricating

The most frequently used process for shaping of metal powders is the double-sided pressing in dies. The properties of the green compact resulting from this pressing process, such as the green density, are essential for the final density of the sintered component and thus for the mechanical properties, like tensile strength and fatigue strength. In general, green properties are dependent on material- and process-specific factors. For instance, the reduction of friction during pressing has a positive effect on compressibility. Usually, in order to reduce friction the used powders are “lubricated” by adding a lubricant (wax) to the powder in small amounts and subsequently mixing it. An alternative method is the die lubrication, where a thin lubricant is applied to the die wall by means of a nozzle prior to each pressing operation. This leads to various advantages, such as higher green and sintered densities, lower density gradients and the elimination of the dewaxing process. However, the application of this lubrication method is not widely used. The reasons for this are mainly the extra efforts, such as the additional process step, but also problems with the production of complex geometries.A highly promising approach to counteract these disadvantages while at the same time benefiting from the advantages of a die lubrication is the application of self-lubricating coatings. Consequently, the aim of the project is to validate the suitability of self-lubricating coatings in die pressing of metal powders to directly improve the green or indirectly improve the sintered properties.The investigations are carried out with two coatings and a steel powder (with and without lubricant/wax). For this purpose the characterization of the powder and the tool design are carried out. Besides the influence of the compression pressure on the resulting relative density, the dependencies between the different lubrication strategies and the green strengths are determined via pressing investigations. In order to interpret the results, the force profiles are recorded during pressing and correlated with the material characteristics. After that, the green parts are sintered in order to show the influences of the investigated lubrication strategies on the final material properties. For this, micrographs are created and density and hardness distributions are determined. By analyzing the determined characteristic values (density, hardness, pressing and ejection forces) as a function of the lubrication strategy, the potentials of self-lubricating die coatings should be emphasized. Finally, the acquired knowledge should be transferred to complex component geometry, including a comparative study of the material properties.

金属粉末塑造最常用的过程是模具的双面压力。由这种压迫过程（例如绿色密度）产生的绿色紧凑型的性质对于烧结成分的最终密度至关重要，因此对于机械性能，例如拉伸强度和疲劳强度。通常，绿色性质取决于材料和特定于过程的因素。例如，压迫过程中摩擦的减少对可压缩性有积极影响。通常，为了减少摩擦，使用的粉末通过少量添加润滑剂（蜡）来“润滑”，然后将其混合。另一种方法是模具润滑，其中每次按压操作之前通过喷嘴将薄润滑剂施加到模具壁上。这会带来各种优势，例如较高的绿色和烧结密度，较低的密度梯度以及消除脱水过程。但是，这种润滑方法的应用并不广泛使用。这样做的原因主要是额外的努力，例如额外的过程步骤，但同时生产复杂的几何形状。一种应对这些灾难的高度希望的方法，同时受益于润滑的优势，是自润滑涂料的应用。因此，该项目的目的是验证在金属粉末压力压力中直接使用两种涂料和一个钢粉（带有和不带有润滑剂/蜡）进行投资的适用性。为此，进行粉末和工具设计的表征。除了压缩压力对所得相对密度的影响外，不同的润滑策略与绿色强度之间的依赖性还可以通过紧迫研究确定。为了解释结果，在按压期间记录了力剖面，并与材料特征相关。之后，绿色部分被烧结，以表明所研究的润滑策略对最终材料特性的影响。为此，创建显微照片并确定密度和硬度分布。通过将确定的特征值（密度，硬度，压力和弹出力）分析为润滑策略的函数，应强调自润滑涂层的潜力。最后，应将获得的知识转移到复杂的组分几何形状，包括对材料特性的比较研究。