残余应力对涂覆WC-17Co涂层的Ni718合金弯曲疲劳寿命的影响

Effect of residual stress on bending fatigue behaviors of Inconel 718 coated with WC-17Co

摘要:

利用超音速火焰喷涂技术在Ni718合金表面制备WC-17Co涂层，对喷涂后的试样进行150℃? h 和300℃? h 保温热处理，利用Almen试片曲率法计算不同热处理条件下涂层中的残余应力，利用反复弯曲试验测试试样的疲劳寿命，分析残余应力对试样疲劳寿命的影响。结果表明在疲劳循环过程中，裂纹在涂层中萌生并向涂层/基体界面处扩展，最后扩展至基体内部形成最终断裂。涂层中的残余压应力能够抑制疲劳裂纹的产生和扩展。当经过保温处理后涂层中的残余压应力降低，导致试样的疲劳寿命随热处理的温度上升而下降。

Abstract:

An Inconel 718 alloy was coated by WC-17Co using a high-velocity oxygen fuel (HVOF) thermal spray process. The residual stress of WC-17Co coating under different heat-treatment conditions was investigated. The effect of residual stress on bending fatigue life of the coated alloy was discussed. It was found that fatigue cracks were initiated at the WC-17Co coating and propagated to the alloy substrate. The compressive residual stress generated during HVOF process could restrict the initiation and propagation of cracks. The absolute value of the compressive residual stress in WC-17Co coating decreased after annealing treatment, resulting in a lower fatigue life of the coated specimens.