柴油机排气阀盘面断裂的失效分析

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第 6卷 第 4期 肖晓玲，等：柴油机排气阀盘面断裂的失效分析 275Failure analysis of exhaust valve in diesel engineXIAO Xiaoling，KUANG Min，LE YoushuDPpt.of New Material，Guangdong General Research Institute of Industrial Technology，Guangzhou 510650ChinaAbstract：The failure of the exhaust valve was investigated using the optical microscope，SEM and EDS。

The resuIt showed that the fracture of valve was mixture of inter-granular and trans-granular fracture withcharacteristic of herringbones，river patterns and dimples.Corruption oxidation action happened with theinclusion and oxide during the fracture.Corruption oxidation and the interaction of high frequency impactstress and heat stress resulted in fatigue fracture in the valve。

Key words：diese1 engine；exhaust valve；fracture；failure analysis， ， ， ， ， m m ' l ， ， ， ' l ， ' ' ' l m l ， ' ' ， l l l ' I ' l ' ' ， l l l l l l l l l ， l ' ， l ' l l l I I I I l l ， ， l ， l ' ' ' ' ， ， ， (上接第 239页)Protective performance ofof bothcoatings prepared by plasma spraying using the powdermicro and nano AI2O3-13 wt TiO2DENG Chunming 。ZHANG Xiaoshui ，MAO Jie ，ZHANG Jifu ，LIU Min ，DENG Changguang1.Guangdong General Research Institute of Industry Technology (Guangzhou research institute of non-ferrousm tals)。G 口 gzhD 510650，China；2.AVICSouth Aviation Industry Limited Corporation，Zhuzhou 412002，ChinaAbstract：A12 03-1 3wtTiO2 coatings were deposited on Q235 steel by air plasma spraying(APS)usingboth micro and nano A1，O3-13wt TiO2 powder as feedstock.The microstructure，phase compositions andmicro-hardness for as-sprayed coatings were examined.The protective properties Oboth micro and nanoA12O3-13wt%TiO2 coatings were investigated and compared including resistance to sand abrasion and elec-trochemical corrosion.The results showed that relatively denser coating with a mixture Of micro and nano-structure by nano A12O3-13wt TiO2 powder was fabricated by far higher plasma power than that appliedin coating prepared by micro A12O3-13wt TiO2 powder.The as sprayed nano A1203-13wtTiOz coatingexhibited better resistance to sand abrasion and electrochemical corrosion，indicating that nanostructuredAl2 O3-1 3 wtTiO2 coating showed better protective performances。

Key words：air plasma spraying；nanostructured A1203-13wtTiOz coating；protective performance