喷油器体的失效分析

Failure Analysis on Injector Body

经过850℃×2 h油淬、-70℃×1.5 h冷处理和500℃×4.5 h回火处理的42CrMo钢喷油器体在进行可靠性验证时发现开裂。对开裂的喷油器体进行了宏微检验、断口分析、化学成分分析、硬度和冲击性能检测和金相检验。结果表明:喷油器体高压油道内壁有机加工缺陷,裂纹起源于高压油道内壁,是疲劳断裂;硬度、冲击韧度不合格导致喷油器体承载性能差是喷油器体开裂的主要原因;喷油器体有较严重的带状组织,进一步降低了喷油器体的疲劳性能,是其开裂的原因之一。

When verified for reliability 42CrMo steel injector body,austenitized at 850℃for 2 h and quenched in oil,cold treated at-70℃for 1.5 h,and tempered at 500℃for 4.5 h,was found cracking.The macro-examination,fracture test,chemical composition analysis,hardness and impact property measurements,and metallographic examination were performed on the cracked injector body.The results showed that(a)the injector body exhibited machining defects in its high pressure oil duct inner wall from which the crack originated,was fatigue failure;(b)the injector body cracking stemmed predominantly from unqualified hardness and impact toughness thereby poor bearing capacity;and(c)the injector body displayed more severe banded structure which resulted in further reduction in its fatigue property,was one of the cause of its cracking.