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对GH742镍基高温合金紧凑拉伸件预制裂纹,并分别进行1次及3次搭接激光冲击处理,利用复型技术和光学显微镜研究了镍基合金的裂纹起源、裂纹分布及尺寸演化全过程。结果表明,未作激光冲击强化试样形成的是沿晶裂纹,晶界处大量位错塞积群造成很高的应力集中;而经激光冲击强化后试样在远离冲击强化区域以裂纹群的形式萌生,且大约集中在同一时段萌生,疲劳后期萌生的新裂纹条数不多,且激光冲击作用的次数越多,裂纹扩展速率越小,激光冲击处理产生的强化效应能大大降低裂纹扩展速率,在某些强化区还能明显提高应力强度因子门槛值。
The pre-crack of GH742 nickel-based superalloy compact tensile member was preformed, and the lapped laser shock treatment was carried out once and three times respectively. The origin of crack, distribution of crack and the whole process of size evolution of Ni-based alloy were studied by using complex technology and optical microscope . The results show that there is a large stress concentration caused by a large number of dislocation plugging groups along the crystal crack along the grain crack without being strengthened by laser shock. When the laser shock is intensified, And the number of new cracks is small, and the more the number of laser shocks is, the smaller the crack propagation rate is, and the strengthening effect produced by laser shock treatment can greatly reduce the crack growth rate , In some areas can also be significantly enhanced stress intensity factor threshold.