哈氏合金X表面改性后的微观结构及腐蚀性能研究

Microstructure and Corrosion Property of Hastelloy X by Surface Modification

为提高航空发动机燃烧室内壁材料哈氏合金X(Hastelloy X)的腐蚀性能,利用强流脉冲电子束(high current pulsed electron beam,HCPEB)对哈氏合金X进行不同轰击次数的表面改性处理,研究改性前后试样的微观结构和电化学腐蚀性能变化规律。结果表明,HCPEB轰击使合金表面发生熔化,易熔相喷发形成熔坑形貌;随着轰击次数增加,表面熔坑数量减少,尺寸变大,金属表面呈现波浪形褶皱形貌。轰击后试样表面形成厚约1~3μm的重熔层,在其下方形成厚度为3~40μm不等的热影响区,随着轰击次数的增大,重熔层以及热影响区的范围增加,表面晶粒尺寸先变小后增大。HCPEB轰击还可在表层诱发塑性变形,出现滑移带等变形结构;电化学实验结果表明,HCPEB轰击提高了试样在模拟海水和酸性溶液中的耐腐蚀性能,其中低次轰击(1、5次)相比高次轰击(10、20次)后的样品腐蚀性能更好。这是由于HCPEB引起的重熔使表面组织分布均匀化,电化学特性相对一致,同时晶粒细化促进了表面致密连续的钝化膜的形成,对基体保护作用增强。HCPEB会引起金属表面结构变化,使哈氏合金X的腐蚀性能提升,低次轰击后(1、5次)的样品抗腐蚀性能最佳。

The work aims to improve the corrosion performance of Hastelloy X which is the wall material of aero-engine combustion chamber.High current pulsed electron beam(HCPEB)was applied to modify the surface of Hastelloy X with different times of bombardment,the microstructure and electrochemical corrosion properties of the samples before and after modification were investigated.After HCPEB,bombardment caused the surface of Hastelloy X to melt,the fusible phase ablated and erupted,resulting in the formation of crater morphology.With the increase of HCPEB treatment times,the number of melting pits on the surface decreased,the size becamelarger,and the metal surface presented wavy fold morphology.After bombardment,a melted layer with thickness of about 1~3μm was formed on the surface of the sample,and the heat-affected zone with thickness of 3~40μm was formed below it.As the times of bombardment increased,the range of the melted layer and the heat-affected zone increased,and the surface grain size first decreased and then increased.HCPEB induced plastic deformation on the surface layer,resulting in deformation structure such as slip band.Electrochemical experiments showed that HCPEB improved the corrosion resistance of the samples in simulated seawater and acidic solution,and the corrosion resistance of the samples with low modification times(1,5 times)were better than that of samples with high modification times(10,20 times).This was because the remelting caused by HCPEB made the distribution of surface elements more uniform,the electrochemical properties became relatively uniform;at the same time,grain refinement promoted the formation of a dense and continuous passive film on the surface and enhanced the protective effect on the matrix.In conclusion,HCPEB changed the structure of metal surface and improved the corrosion properties of Hastelloy X.The samples with low modification times(1,5 times)had the best corrosion performance.