电火花加工镍基合金的热影响层研究

Study of Heat Affected Zone of Nickel Alloy by EDM

为去除电火花加工后的镍基合金热影响层,进行了大量镍基合金的电火花加工实验。通过对电火花加工后的镍基合金亚表面合金颗粒的金相观察发现,长时间非正常放电加工的样品亚表面出现了明显的晶粒细化,而正常放电加工的亚表面晶粒与基体晶粒尺寸相仿。根据热传导理论,通过模型仿真了在电火花放电后的工件亚表面温度场分布,估算出热影响层的厚度。结果显示,在粗加工条件下可能发生高温性能变化的表层金属厚度值小于8μm,在精加工条件下可能发生高温性能变化的表层金属厚度值小于2.5μm。

To remove the heated affected zone(HAZ)by electrical discharge machining(EDM)in the following process,extensive experiments of nickel alloy by EDM are carried out.After microstructure observation of HAZ of nickel alloy under a long time abnormal discharge,it was found that the grain size in HAZ becomes smaller than that far from the machined surface.Under normal discharge conditions,the grain size of machined surface has no significant change.To estimate the thickness of HAZ,a heat conduction model is used to simulate the temperature distribution of discharges in workpiece.Based on simulation results,the possible HAZ thicknesses in rough and finish machining are 8μm and 2.5μm respectively.