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球墨铸铁由于高温时强度下降比率小,且能比较经济地制造形状复杂的部件,所以在高性能发动机上得到了应用。其典型部件是球铁活塞。本文研究了对 FCD80球铁用等离子喷涂法覆盖 Al_2O_3陶瓷膜后的高温疲劳特性。结果表明,喷涂陶瓷膜与未喷涂时相比,高温疲劳强度提高了10%。其原因是:由球铁表面微小气孔(裂纹发生源)引起的疲劳裂纹在未开裂前就被陶瓷膜所抑制。即陶瓷膜延缓了由球铁表面微小气孔引起的疲劳裂纹的扩展。
Ductile iron has been used in high-performance engines due to its low rate of strength reduction at high temperatures and its ability to manufacture more complex-shaped parts economically. The typical part is a ductile iron piston. In this paper, the fatigue properties of FCD80 ductile iron coated with Al_2O_3 ceramic coating by high temperature plasma spraying were studied. The results showed that the fatigue strength of the sprayed ceramic coating increased by 10% at high temperature compared with that without spray coating. The reason is that fatigue cracks caused by minute pores (sources of crack generation) on the surface of the ductile iron are suppressed by the ceramic film before cracking. That is, the ceramic film retards the propagation of fatigue cracks caused by tiny pores on the surface of the ductile iron.