带中心孔的镍基高温合金GH4049的高温疲劳短裂纹扩展规律

对疲劳试样GH4049镍基高温合金在同一载荷与不同温度下的疲劳短裂纹扩展进行了试验，利用复型技术和光学显微镜观测了裂纹形态演化全过程。发现应力集中条件下的高温疲劳短裂纹扩展主要是单裂系统破坏，随着温度升高，短裂纹逐渐变为多裂系统，并以多裂纹的合并形式进行最终破坏；扩展方式由穿晶到沿晶和穿晶的混合方式进行，温度越高，短裂纹起裂越早，裂纹平均长度越短，短裂纹扩展速率反而越慢。

Study on Groeth Behavior of Elevated Temperature Small Fatigue Cracks in Ni-Base Superlloy GH4049 with a Central Hole

The study of small fatigue cracks development process of Ni-base superalloy GH4049 under same loading at various temperatures is carried out. The evolution process of cracks' length is observed by using a replication method and an optical microscope. It is found that elevated temperature fatigue damage in the condition of concentrative stress is single cracks system. Fatigue damage can change into several systems under the circumstance of higher temperature and damage in the form of combination. These cracks begin to extend from the centers of the grain, and then grow on grain boundaries or centers of the grain. In the meantime, we can see that elevated temperature make cracks begin early and less length of cracks. What is more important is that rate of growth in cracks can decrease with the increase of temperature.