电化学加工YT15硬质合金表面形貌特征实验研究

由于所含碳化物粉末与黏结金属的电极电位差等原因,硬质合金电化学加工的阳极表面蚀除过程较碳钢和其他金属更为复杂.以YT15硬质合金为实验对象,对试件原始表面进行统一加工条件下的研磨处理,使之具有一致的表面状态.在此基础上进行电化学加工实验,以SEM图像结合轮廓曲线,分析表面微观形貌的横向特征和纵向特征,获得表面材料溶解的特点和规律.实验发现,使用不同电解液获得的表面微观形貌特征差异显著,加工过程中的表面微观形态和腐蚀规律及变化特性也各不相同.研究认为,不同电解液产生的不同阳极表面膜特性和硬质合金材料固有的多组分特征是导致这种差异的原因,抑制硬质合金同类材料的边界腐蚀是获得良好加工效果的关键.NaOH去钝化能力较强,溶解速度快,适于成型加工电解液;NaNO_3及NaCl具有良好的钝化成膜能力,阳极膜无序破坏容易导致不均匀腐蚀,纯电化学加工不容易获得良好的加工效果,但通过合理施加外力控制阳极膜的有序破坏,则可提高表面质量,具有作为复合光整加工电解液的潜力;H_2SO_4+H_3PO_4成膜较均匀,活化作用较好,具有抑制材料不均匀溶解的能力,适用于具有一定表面质量要求条件下同时达到特定成型效果的加工.

Experimental study of surface topography characteristics of YT15 cemented carbide by electrochemical machining

Due to the electrode potential difference between cemented carbide powders and bonding metals, the anode surface erosion process of cemented carbides in electrochemical machining is more complex than carbon steels and other metals. YT15 cemented carbide is used as the workpiece material for studying surface erosion process. All the YT15 samples are polished under the same procedures for consistent surface conditions. Both planar and vertical features of the surfaces are studied by SEM observations and surface profile analysis by electrochemical machining. Characteristics of the surface material dissolution are obtained. It is found that the surface micro-topography and the erosion process are strongly affected by the electrolyte composition. The results are attributed to the different properties of the generated anode surface films and the multi-component characteristics inherent to the cemented carbide. Suppression of the boundary erosion of the same compositional material is helpful in getting good machining performance. According to the experimental results, NaOH is considered a suitable electrolyte for mold machining because it has good depassivation ability and high dissolution rate. NaNO 3 and NaCl have good ability of forming passivation films, but the anodic film is easily destroyed leading to non-uniform erosion, which makes it difficult to obtain a good result by electrochemical machining. However, surface quality can be improved by optimizing the machining conditions and avoiding non-uniform erosion. Therefore, NaNO 3 and NaCl have the potential to be used as an electrolyte for finishing processes. H 2SO 4+H 3PO 4 are good for making uniform films and have activation capability in suppressing uneven dissolution, so they can be used when both surface quality and molding efficiency are required.