The Mechanism of Grain Boundary in Hydrogen Embrittlement of Inconel 690 Alloy
The effects of grain boundary on tensile deformation behaviors of Inconel 690 alloy precharged with hydrogen were investigated by changing the grain size, in order to clarify the mechanism of hydrogen embrittlement of the alloy. The results show that tensile strength and elongation of precharged alloy decreases, and the decreasing degree is gradually reduced with the increase of grain size, indicating that the interaction between grain boundary and hydrogen dominate hydrogen embrittlement of Inconel 690 alloy. Hydrogen could easily migrate towards the grain boundaries following the moving dislocations during tensile, and then enrich at grain boundaries, when the strain rate is relatively low. Thus, the accumulation of hydrogen results in dislocations pile-up, and if such dislocations pile-up reaches a critical degree, the hydrogen-induced cracking will initiate at grain boundaries, which leads to the brittle intragranular fracture characteristics. That means hydrogen-enhance dislocation pile-up is the main reason for hydrogen embrittlement of Inconel 690 alloy. Therefore, how to control the ratio of grain boundary could be considered as the key to avoid the hydrogen embrittlement.
KeywordsInconel 690 alloy Grain boundary Hydrogen embrittlement
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