摘要
对断裂的某船用柴油机排气阀进行了化学成分和显微组织分析及硬度测试。结果表明,排气阀材质的化学成分和硬度都符合材料要求,但在排气阀内部发现少量氮化钛夹杂;断裂的排气阀断口具有典型的脆性断裂特征;排气阀在使用过程中,阀体表面氧化皮逐步脱落,氧化层向基体不均匀扩展,在阀杆表面形成多个裂纹源;阀杆机加工部位可能有残余应力存在进而导致阀体在加工位置断裂;另外,材料内部存在的夹杂对材料的性能有一定影响,使其未能完全满足排气阀高温腐蚀运行工况的要求。
An investigation was made on the fracture of a marine diesel engine exhaust valve. The microstructure and chemical composition as well as hardness were performed by optical microscopy, optical spectrometer, scanning dectron microscopy and hardometer, respectively. The experimental results show that the chemical composition and the hardness value of the broken exhaust valve reached the technique requirement. A small amount of titanium nitride inclusions was found in the exhaust valve. The exhaust valve showed typical characteristics of brittle fracture. The oxide coating on surface of the valve body peeled off gradually and expanded to the substrate of exhaust valve in the course of serving. The valve stem ruptured at the machined position which may result from the existence of residual stress in machined parts. In addition, inclusions existing in the valve may degrade the performance of material. Therefore, the valve material does not meet the operating requirements which need to be used under high temperature and high corrosion environment.
出处
《金属热处理》
CAS
CSCD
北大核心
2012年第8期122-125,共4页
Heat Treatment of Metals
关键词
排气阀
断裂
失效分析
exhaust valve
fracture
failure analysis
