Cracking failure analysis of nozzle for high pressure common rail injector and its optimization
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.
common rail systeminjector nozzleintergranular crackinghydrogen stress corrosion
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维普
