工作液电导率对高Nb-TiAl合金电火花加工小孔精度影响

采用PAAS（聚丙烯酸钠）的水溶液作为电火花小孔加工工作液，研究了工作液电导率对高Nb-TiAl合金(Ti-44Al-8.5Nb-0.2Mo-0.2B)电火花加工小孔孔径精度、孔口微观形貌的影响规律，结果表明，随着电导率增大，其中的载流子数量将不断增多，在放电和电解溶解的共同作用下，小孔放电间隙迅速增大，小孔精度下降，此时放电间隙增大幅度不足以快速排除电蚀产物，电蚀产物在冷却的孔壁上再凝固，重铸层厚度快速增加。电导率增长后期，击穿电压不断下降，电解作用减弱，工作介质流动交换充足，电蚀产物快速排除，放电间隙和再铸层厚度增长速度均减慢。

Research on the Influence of Dielectric Conductivity on the Hole Precision in EDM of Nb-TiAl Alloy

This paper has studied how the conductivity of PAAS solution will influence the processability of high Nb-TiAl Alloy(Ti-44Al-8.5Nb-0.2Mo-0.2B)EDM, such as aperture accuracy and the orifice surface microsmic topography.The result shows that with the increase of the conductivity and the number of carriers will continue to increase. Under the combined action of discharge and electrolytic dissolution, the gap of the small hole is rapidly increasing and the accuracy of the small hole decreases. The increase of the discharge gap is not enough excluding the corrosion product and the corrosion product is resolidified on the wall of the cooled hole at the same time, so the thickness of the reclaimed layer increases rapidly. In the later stage of conductivity increasing, the breakdown voltage decreasing, the electrolysis effect being weakened, the working medium well exchanged and the corrosion product being quickly removed, the increment speeds of discharge gap and the thickness of the cast layer are slowed down. The conclusion has a certain practical value for improving the hole accuracy machining of High-niobium Titanium Aluminum Alloy.