高硅钼球铁排气歧管高温氧化开裂原因分析

High temperature oxidation cracking analysis of exhaust manifold made of high Si-Mo nodular cast iron

通过电镜、金相、能谱分析等手段对高硅钼耐热球铁的排气歧管开裂进行综合分析。该耐热铸铁在高温条件下,氧化由外向内推进,由于材料表面不当的应力强度及分布在氧化区诱发了裂纹,同时,氧化层的破裂造成氧化呈管道向内突进;而排气歧管基体中局部区域石墨的非球形态促进了裂纹的萌生及扩展。因此该排气歧管的开裂为氧化腐蚀疲劳开裂。

By means of SEM, EDS and metallography microscope, the cracking exhaust manifold made of high Si-Mo nodular cast iron were analyzed and tested. The results show that at high temperature, the oxidation of cast iron extends from surface to inside, the improper intensity and distribution of stress result in oxidation cracks, at the same time, the rupture of oxidation layers promotes the pipeline oxidation. Some non-spheroidal graphite also accelerates the initiation and propagation of cracks. So the crack of exhaust manifold belongs to oxidation erode fatigue crack.