Plasma nitriding of depleted uranium
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摘要: 为了提高贫化铀表面耐腐蚀性能，利用三种等离子氮化技术（等离子源离子注入Plasma Source Ion Implantation——PSII、辉光放电等离子氮化Glow Discharge Plasma Nitriding——GDPN、空心阴极等离子氮化Hollow Cathode Plasma Nitriding——HCPN）在贫化铀表面制备了氮化层。通过多种材料分析手段对氮化层成分、结构、化学状态进行了分析。三种氮化层中的氮化物都以α-U2N3为主，由于金属铀与氧的亲和力较强，三种等离子氮化过程都不同程度地引入了氧杂质。PSII可以突破热力学平衡，将部分氧化物转化为氮化物。GDPN和HCPN则通过表面反应和热扩散形成氮化物层。HCPN技术对控制氧杂质有一定优势，可以显著降低氮化层中氧杂质含量。湿热腐蚀和电化学测试表明，等离子氮化可以明显提升贫化铀的抗腐蚀性能，HCPN和GDPN的提升程度要优于PSII，而HCPN技术最优。本文的研究结果可为活性金属的等离子氮化处理提供参考。Abstract: To enhance the corrosion resistance of depleted uranium surfaces, a comparative analysis was conducted to evaluate the efficacy of three plasma nitriding technologies: Plasma Source Ion Implantation (PSII), Glow Discharge Plasma Nitriding (GDPN), and Hollow Cathode Plasma Nitriding (GDPN). The composition, structure and chemical state of the nitrided layers were analysed using a range of material analysis methods. The nitrides present in the three nitrided layers are predominantly α-U2N3. Due to the strong affinity between uranium metal and oxygen, all three plasma nitriding processes have introduced oxygen impurities to varying degrees. PSII is capable of breaking through the thermodynamic equilibrium and converting some of the oxides into nitrides, while GDPN and HCPN can form nitrides through surface reactions and thermal diffusion. HCPN technology has certain advantages in controlling the oxygen impurities, and can significantly reduce the oxygen impurities in the nitrided layer. The results of the wet heat corrosion and electrochemical tests demonstrate that plasma nitriding can markedly enhance the corrosion resistance of depleted uranium. The degree of improvement achieved by HCPN and GDPN is superior to that of PSII, with HCPN technology exhibiting the most favourable outcome. The findings of this study could provide a reference for plasma nitriding treatment of reactive metals..
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Key words:
- depleted uranium /
- plasma nitriding /
- surface treatment /
- corrosion resistance
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图 5 PSII样品和GDPN样品湿热腐蚀前后的AES分析数据
Figure 5. AES data of PSII sample and GDPN sample before and after wet heat corrosion
图 6 HCPN样品、GDPN样品、PSII样品、未处理样品的电化学极化曲线
Figure 6. Electrochemical polarization curves of HCPNsample, GDPN sample, PSII sample, and untreated sample
表 1 实验材料杂质
Table 1. Impurities of experimental materials
experimental
materialimpurity content/10−6 carbon nitrogen oxygen H2O others uranium 200 45 ＜150 nitrogen ＜3 ＜3 ＜5 ＜1 
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表 2 主要工艺参数
Table 2. Process parameters
process base
presure/Pavoltage/
kVfrequence/
kHzpulse
width/μscurrent density/
(mA·cm−2)process
time/hvacuum
temperature/℃PSII 8×10−4 50 0.4 40 ～0.1 2 220 GDPN 3×10−4 0.9 60 1.5 ～1 2 350 HCPN 3×10−4 0.6 60 0.5 ～20 2 130
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