NZ2锆合金碘致应力腐蚀

Iodine-Induced Stress Corrision of NZ2 Zirconium Alloys

研究了NZ2锆合金板材在不同温度、不同浓度的碘蒸气中的力学行为,并进一步通过扫描电镜观察其断口形貌。结果表明,试验温度为400℃,其发生应力腐蚀的临界碘蒸气压约为102Pa;横向试样较轧向试样更具应力腐蚀敏感性;温度升高能够促进裂纹尖端的应力释放,有利于碘能被更有效地吸附到裂纹尖端,加快对锆合金的腐蚀作用,从而降低了应力腐蚀的临界碘浓度。在高温碘蒸气中,断口腐蚀产物主要为锆的氧化物;虽然碘蒸气对锆有较强的腐蚀作用,但是不足以穿透其表面的保护膜,而局部变形则可以促进碘对金属锆的腐蚀。

The mechanical properties of NZ2 zirconium alloy sheets were investigated in different-concentration iodine stream at different temperatures. The fracture morphology was also observed by SEM. Results show that the critical iodine stream pressure for stress corrosion of NZ2 alloy is 102 Pa at 400℃. The cross rolling samples has better stress corrosion sensitivity. Temperature increase can accelerate the stress release of crack tips and it is good for effective absorption of iodine to crack tips. Therefore corrosion of the alloys becomes more serious and the critical iodine concentration is decreased. In the high-temperature iodine stream, the main corrosion products are oxides of Zr. Although iodine stream can heavily corrode the Zr alloys, it can not penetrate through its protective film on the surface. However, local deformation can accelerate the corrosion of Zr by iodine.