发动机排气门断裂失效分析

Failure Analysis of Fracture of an Engine Exhaust Valve

气门作为发动机的一个重要零部件,直接影响着发动机动力的正常发挥,因此气门要有足够的刚度和强度,良好的耐磨性、耐高温性,以保证其在恶劣环境下正常工作。本文主要论述汽油机在进行冷热冲击试验时排气门出现断裂,经过对故障件断口、化学成分、金相组织、硬度以及受力情况分析,结果发现是由于排气温度高于气门所能承受最高温度导致在颈部发生多源疲劳断裂,通过排气门改进设计并进行试验验证问题得以解决。

The valve has a direct effect on proper operation of an engine powertrain as an important component of engine. Therefore, it requires sufficient stiffness and strength with better abrasion resistance and high-tem- perature resistance in order to ensure its proper operation under severe environment. The exhaust-valve frac- ture occurred during cold-and-hot shock test of a particular engine is basically discussed in this paper. After analyzing the failed component fracture, chemical composition, metallographic structure, hardness and load condition, results indicate that multi-source fatigue fracture occurs at neck area largely because exhaust tem- perature exceeds the highest temperature which valve can withstand. This problem is ultimately solved by im- proving design of exhaust valve and performing test validation.