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本文对铸造镍基高温合金光滑板试样(经过热等静压处理)疲劳裂纹的形成与扩展进行了研究。扫描电镜观察到裂纹在碳化物、显微疏松及其附近的基体上形成。着重观察了裂纹从20～2000μm长度范围内的扩展行为,以及从微观裂纹到宏观裂纹转变的特征。从裂纹长度和循环次数的关系可以看到小裂纹(<1000μm)的扩展是不连续和不规则的,它表明显微组织(特别是晶界)对裂纹扩展速率有影响。但是,用裂纹的平均扩展速率仍可以描述小裂纹的长大过程,小裂纹的扩展速率至少比长裂纹的扩展速率高一个数量级。
In this paper, the formation and propagation of fatigue cracks on cast Ni-base superalloy smooth plate specimens (after hot isostatic pressing) were studied. Scanning electron microscopy showed cracks in the carbide, microscopic loose and in the vicinity of the matrix formed. The behavior of the crack propagation along the length of 20 ~ 2000μm and the characteristics of the transition from micro-cracks to macro-cracks were observed. It can be seen from the relationship between the crack length and the number of cycles that the propagation of small cracks (<1000μm) is discontinuous and irregular, which indicates that the microstructure (especially the grain boundaries) has an effect on the crack growth rate. However, the average growth rate of cracks can still describe the growth of small cracks, and the propagation rate of small cracks is at least an order of magnitude higher than the propagation rate of long cracks.