激光冲击对K403镍基合金高温疲劳性能和断口形貌的影响

Effects of Laser Shock Processing on High Temperature Fatigue Properties and Fracture Morphologies of K403 Nickel-Based Alloy

对K403镍基合金涡轮叶片进行激光冲击强化(LSP),利用高温高低周复合疲劳试验验证其强化效果。试验结果表明:冲击后裂纹源区附近平坦区较冲击前变大,在快速扩展(FCG)区,激光冲击强化后疲劳条纹间距减小,有大量二次裂纹产生。且强化后在材料表层会引发晶粒细化以及高残余压应力,但在550℃/150min保温下,残余应力部分发生松弛,但是表层细化结构有很好的热稳定性。相比冲击前样件,激光冲击强化后涡轮叶片疲劳寿命提高了140%。热松弛后的残余压应力和表面晶粒细化是镍基合金疲劳寿命提高的主要原因。

Laser shock processing（LSP）is carried out on K403 nickel-based alloy turbine blades and the high temperature high and low cycle complexed fatigue tests are conducted to verify the reinforcement effect.The results of the fatigue experiments show that a greater flatness area near the fatigue crack initiation（FCI）is induced by LSP,the fatigue striation spacing on the fatigue crack growth（FCG）area decreases and lots of second cracks are generated after LSP.Grain refinement and high residual compressive stress on the surface layer are induced by LSP.But when the K403nickel-based alloy after LSP is subjected to heat treatment at 550℃for 150 min,apart of residual compressive stress has got relaxation while the refined structure has still remained good thermal stability.Compared with the untreated samples,the fatigue life of turbine blades is increased by 140% after LSP.The grain refined structure and residual compressive stress after relaxation are the main causes of improvement of nickel-based alloy fatigue life.