核电站大型巴氏合金轴瓦失效分析

利用光学显微镜、扫描电镜和能谱等分析手段，对巴氏合金轴瓦表面多次发生粘结和开裂进行了检验和分析。结果表明，在巴氏合金层中存在着组织分层，化合物相呈区域性偏析和聚集，轴瓦结合面附近存在大量疏松、孔洞等浇注工艺不当所形成的铸造缺陷；加之结合面附近背底金属中氢含量较高，轴瓦长期在一定温度和应力下工作，氢的不断扩散和聚集最终在巴氏合金表面形成氢鼓泡。上述缺陷的存在，使轴瓦在运行过程中易造成应力集中导致裂纹的萌生和扩展。最终造成局部润滑条件恶化而导致粘结和开裂失效。

FAILURE ANALYSIS ON BABBITT ALLOY BUSH FOR NUCLEAR POWER PLANT

The thorough analysis was made on adhesive failure and cracking in the surface of Babbitt bush. Segregation, mass and delaminating phenomenon were found in microstructure of Babbitt alloy layer, and also found a lots of porosity near the interface between body and Babbitt alloy layer, formed from unsuitable foundry processing. The cast defects were apt to form stress concentration and finally resulted in cracks initiation and propagation. The chemical analysis showed that the hydrogen content near interface were higher than that in others, the swell would occur in the surface of Babbitt alloy with hydrogen diffusing and massing when the bush run with high temperature and stress, which would distort the lubricant condition and form adhesive failure and cracks.