通过光学显微镜、扫描电镜等手段,研究了高SiMo蠕铁在不同热疲劳试验上限温度Tmax(600℃、700℃、800℃、900℃)下的微观组织以及抗热疲劳性能.结果表明,随着上限温度升高,珠光体以及(FeMo)3C加速消失,残留的(FeMo)3C会明显促进热疲劳裂纹的产生,并使裂纹扩展方式发生变化,导致蠕铁抗热疲劳性能下降.Tmax为600～800℃时,主裂纹的扩展路径是优先沿着蠕虫状石墨长轴扩展,其次顺带连接沿线已萌生裂纹的球墨或者(FeMo)3C.Tmax为900℃时,主裂纹的扩展路径是沿着蠕虫状石墨长轴方向扩展的同时,沿垂直方向以龟裂加宽,顺带连接球状石墨和孔洞,且裂纹带较宽,导致高SiMo蠕铁的抗热疲劳性能急剧恶化.%By the optical microscope (OM) and scanning electron microscope (SEM), the microstructures and thermal fatigue resistance of the high silicon-molybdenum vermicular graphite cast iron under various thermal cycle maximum temperature Tmax(600℃, 700℃, 800℃ and 900℃) were studied. The results show that with Tmax increasing, the pearlite and (FeMo)3C in the vermicular graphite cast iron disappear faster, and the residual (FeMo)3C significantly promotes the formation of thermal fatigue cracks. With increasing Tmax, the thermal fatigue resistance of the vermicular graphite cast iron decreases and the crack propagation mode changes. When Tmax=600-800℃, the propagating route of the main crack in the vermicular graphite cast iron is preferably along the long axis of the vermicular graphite, simultaneously connecting the ductile graphite or (FeMo)3C carbides which cause cracks initiated along the main crack. When Tmax=900℃, the main crack propagating paths are both along the long axis of vermicular graphite and along the vertical direction to widen the crack, connecting the spherical graphite by the way; since the crack band is relatively wider, the thermal fatigue resistance of the vermicular graphite cast iron deteriorates sharply.
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