定向凝固镍基高温合金上激光熔覆Inconel 738的裂纹敏感性研究

针对定向凝固镍基高温合金叶片的强化与修复需求,研究了在定向凝固镍基高温合金基体上激光熔覆Inconel 738的裂纹敏感性问题.在定向凝固镍基高温合金基体上激光熔覆Inconel 738合金对裂纹非常敏感,所产生的裂纹为热裂纹,由定向凝固基体晶界处引发并穿过界面向熔覆层发展;多层熔覆过程中熔覆层间也会产生热裂纹,热裂纹沿晶界纵向扩展.定向凝固高温合金基体晶界处的低熔共晶成为主要的裂纹源.严格控制激光熔覆过程中的热输入量可以显著降低裂纹敏感性.选择适当的熔覆工艺方法和参数可以在定向凝固镍基合金基体上形成良好冶金结合且无裂纹的基本保持定向凝固特性的熔覆层组织.

Cracking Sensitivity on Laser Cladding Inconel 738 on Directionally Solidified Ni-base Superalloy

The cracking sensitivity of laser cladding Inconel 738 alloys on directionally solidified Ni-base superalloy substrate for the purpose of strengthening and repairing the directionally solidified gas turbine blades was studied. The results indicated that laser cladding of Inconel 738 on directionally solidified Ni-base superalloy substrate was very sensitive to crack. The cracks were mostly the thermal cracks which originated in the grain boundary in the heat affected substrate. The cracks went through the interface between the directionally solidified substrate and the cladding layers, and then developed into multi-deposited cladding layers. Cracks also appeared inside the multi-deposited cladding layers, developing along the grain boundaries directly. The low melting point eutectics between the grain boundaries of directionally solidified Ni-base superalloy substrate were the main sources of the thermal cracks. Strict control of the heat input during laser cladding could dramatically decrease the cracking tendency. Directionally solidified layers were deposited by laser cladding on directionally solidified substrate with good shaping and free of cracks by optimizing the cladding technique and laser parameters.