高压共轨系统喷油嘴开裂失效分析及优化

张进，李凯，王浩，刘井年，许连超

潍柴动力股份有限公司，山东 潍坊   261061

摘要：为解决某高压共轨系统油嘴开裂故障，通过宏观形貌分析、扫描电镜分析、能谱分析、断口金相分析、硬度测试等查找故障原因，并对油嘴材料、结构和工艺进行优化。分析结果表明：机组用燃油中含有P、K等腐蚀性元素形成酸性环境，安装工艺导致油嘴肩胛处存在非对称拉应力，肩胛圆角过小导致应力集中，油嘴表面马氏体组织粗大、硬度高造成的应力敏感是油嘴开裂的主要原因。采取优化油嘴材料，将油嘴肩胛处圆角半径由0.45 mm加大到1.20 mm，在喷油器和高压连接器最终紧固前增加预紧工序等优化措施，优化后油嘴经过4 000 h的耐久试验未开裂，有效解决油嘴开裂故障。

关键词：高压共轨；喷油嘴；沿晶开裂；氢应力腐蚀

Cracking failure analysis of nozzle for high pressure common rail injector and its optimization

ZHANG Jin, LI Kai, WANG Hao, LIU Jingnian, XU Lianchao

Weichai Power Co., Ltd., Weifang 261061, China

Abstract: To slove the nozzle cracking failure in a certain high-pressure common rail system, macro morphology analysis, scanning electron microscopy, energy spectrum analysis, fracture metallographic analysis, and hardness testing, are investigated to find the causes of failure. The nozzle material, structure and process, are optimized.The analysis results show that the presence of corrosive elements such as P and K in the fuel used by the unit created an acidic environment, the installation process leads to asymmetric tensile stress at the shoulder of the nozzle, and the small radius of the shoulder corner causees stress concentration, these factors result in coarse martensitic microstructure and high hardness on the nozzle surface, making it sensitive to stress, which is the primary reason for the nozzle cracking. By improving the nozzle material, increasing the shoulder corner radius from 0.45 mm to 1.20 mm, and adding a pre-tightening step before the final fastening of the injector and high-pressure connector, after 4 000 h of durability testing, the optimized nozzle does not crack, the cracking fault of the oil nozzle has been effectively solved.

Keywords: common rail system; injector nozzle; intergranular cracking; hydrogen stress corrosion