铸钢轮材料在700℃～20℃热循环下断裂机制分析

Fracture Mechanism Analysis of Wheel Cast Steel under Thermal Fatigue Test at 700℃～20℃

研究铸钢车轮材料在700℃～20℃热循环温度幅下热疲劳破坏规律。实验结果发现，试样表面出现大量的氧化腐蚀坑，表面主裂纹优先通过这些腐蚀坑扩展。试样表面的氧化腐蚀及氧化皮剥落均比次表层严重，表面的开裂也加速了次表层裂纹的形核和扩展。断口上的二次裂纹以沿晶为主，穿晶为辅，说明蠕变损伤导致晶界弱化。断口处腐蚀坑和夹杂物的开裂对试样热疲劳损伤有重要的促进作用，同时，断口上和表面的破坏互相促进，加深了试样的损伤程度。

The thermal fatigue fracture behavior of wheel cast steel at 700℃～20℃ is studied by using SEM. Plenty of oxidation etching pits are found on the surface of the specimen after the thermal fatigue test, and the surface principal crack is prone to propagate through these etching pits. Peeling of oxidation film and oxidationdecarbonization are more serious on the surface than on the sub-surface. The damage on the surface also accelerates the formation and propagation of cracks on the sub-surface. The secondary cracks appearing on the fracture are mainly in the intercrystalline form, partly in the transcrystalline form, which shows that creep damage has weakened grain boundaries of the specimen. The impurities cracking and etching pits on the fracture have sped up the damage of the specimen. Meanwhile, the interaction of damage on the surface and on the fracture aggravates the thermal fatigue damage of specimens.