风机叶轮腐蚀开裂机制与预防

Mechanism and Prevention of Corrosion Cracking of Blower Impellers

在微观组织和裂纹形貌观察的基础上,分析了失效叶轮早期腐蚀开裂机制。结果表明,叶轮失效是Cl-促进下应力腐蚀开裂造成的。在叶轮本体上焊接扰流板后,焊接热循环使靠近熔合线的叶轮本体组织发生了显著变化,其中二次相的析出直接导致了叶轮本体耐蚀性降低,进而在工作应力和焊接残余应力联合作用下发生了应力腐蚀开裂,分析表明,叶轮本体上工作应力非均匀分布,越靠近叶轮心部,工作应力越大,越容易引发应力腐蚀开裂。进而提出了去除靠近叶轮心部4个扰流板的预防措施并进行了生产验证,结果表明,这一做法可有效预防叶轮过早应力腐蚀开裂。

Based on observation of microstructures and crack morphologies,the mechanics of premature corrosion cracking of the scrapped impeller has been investigated. The results have shown that the failure of the impeller was due to stress corrosion cracking promoted by chloride ions. Weld thermal cycle made significant changes to the microstructure of the impeller body near fusion line after welding spoilers on the impeller body. The precipitation of secondary phases led to degradation of corrosion resistance of the impeller body and then stress corrosion cracking under the combination function of welding residual stresses and working stresses. Working stresses on the impeller body are not evenly distributed,the closer to the impeller heart,the greater stresses and the more easily causing stress corrosion cracking. This paper proposed a prevention method for removing the 4 spoilers near the impeller heart. On-site verification shows that this method is effective to prevent premature stress corrosion cracking of the impeller.