Characterization of physical processes in the process zone during free jet-based plasma electrolytic polishing

基于喷射的等离子体电解抛光(Jet-PEP)可以对由导电材料制成的零件表面进行局部抛光，而不需要掩膜，并且消耗的环保电解液很少。它基于熔池中的等离子体电解抛光，其中的化学-物理过程刺激在工件表面形成局部蒸气-等离子区(VPZ)。这是在施加直流电压时发生的，前提是使用了适当的工件材料、电解液成分和电解液温度的组合。这一VPZ是该进程成功启动和持续的基本要求。然而，在Jet-PEP的背景下，对这一带的形成和连续性的研究还不够充分，因此对它的了解很少。工艺条件的具体和可重复性调整几乎是不可能的，特别是在少数已知参数组合发生偏差的情况下。在本研究项目中，将研究在Jet-PEP过程中电能和热能供应对VPZ起始性和连续性的影响。为此，将自由射流沿着射流的流动方向划分为特征区域。在不同的能量输入下，研究了喷嘴与工件表面工作距离处的比例。通过改变施加的直流电压，可以得到Jet-PEP的工艺初始化和抛光过程的特性电流-电压曲线。此外，还研究了电解液喷射速度对VPZ的形成和连续性的影响，并与电解液温度有关。为此，必须对现有Jet-Pep装置的电和热测量设备进行调整和扩展。VPZ的空间扩展和过程固有的天然气形成将用高速相机和图像评价进行分析。通过记录电流、电压以及电解液和工件温度的时间特性，可以得到基于阳极溶解电荷和电解电荷的充电效率，以及基于热能供应的电解液和工件之间的换热。已加工工件表面的测量分析用于评估局部抛光过程，并能够区分EC和PEP去除过程。基于实验得到的影响变量和子过程的结果，旨在得到电能和热能输入对Jet-Pep过程和VPZ形成的影响的第一个物理模型。

Jet-based plasma electrolytic polishing (Jet-PeP) enables local polishing of part sur-faces made of electrically conductive materials without need for masking and with low consumption of environmentally friendly electrolytes. It based on plasma electro-lytic polishing in a bath, where chemical-physical processes stimulate the formation of a local vapor-plasma-zone (VPZ) on the workpiece surface. This occurs when a DC electrical voltage is applied, provided a suitable combination of workpiece mate-rial, electrolyte composition and electrolyte temperature is used. This VPZ is a basic requirement for the successful initiation and continuity of the process. However, in the context of Jet-PeP, the formation and continuity of this zone has been insuffi-ciently studied and is therefore poorly understood. A specific and reproducible ad-justment of the process conditions is hardly possible, especially in case of devia-tions from the few known parameter combinations. In the present research project, the influence of the electrical and thermal energy supply on the initiation and continuity of the VPZ in the Jet-PeP process will be in-vestigated. For this purpose, the free jet is divided into characteristic zones along the flow direction of the jet. The proportions of which are investigated at the working dis-tance between the nozzle and the workpiece surface at different energy inputs. By varying the applied DC voltage, the characteristic current-voltage curves of the pro-cess initialization and the polishing process will be derived for Jet-PeP. Further-more, the influence of the flow velocity of the electrolyte jet on the formation and continuity of the VPZ in connection with the electrolyte temperature will be investi-gated. For this purpose, the electrical and thermal measurement equipment of the existing Jet-PeP setup has to be adapted and expanded. The spatial expansion of the VPZ and the process-immanent gas formation will be analyzed with a high-speed camera and image evaluation. The charge efficiency based on the electric charge of anodic dissolution and the electrolysis as well as the heat transfer between electrolyte and workpiece based on the thermal energy supply will be derived from the recording of the temporal charac-teristic of electric current and voltage as well as the electrolyte and workpiece tem-perature. The measurement analysis of the machined workpiece surfaces is used to evaluate the local polishing process and enables a differentiation between EC and PeP removal processes. Based on the experimentally received findings on the in-fluencing variables and sub-processes, it is aimed to get a first physical model for the effect of the electrical and thermal energy input on the formation of the Jet-PeP process and the VPZ.