1000MPa級0Cr16Ni5Mo鋼的氫脆敏感性STUDY ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF 1000 MPa GRADE 0Cr16Ni5Mo STEEL

利用升溫脫氫分析(TDS)實驗研究了 1000 MPa 級 0Cr16Ni5Mo 馬氏體不銹鋼的氫陷阱行為.同時,采用慢應變速率拉伸實驗(SSRT)研究了該鋼缺口與光滑試樣的氫脆敏感性,并利用SEM觀察了試樣的斷口形貌.結果表明, 位錯和晶界為該鋼的主要氫陷阱,充氫后缺口試樣與光滑試樣的伸長率均下降明顯,但強度變化不大.隨著氫含量的升高,斷口形貌由韌窩型韌性斷裂向穿晶、準解理斷裂,甚至向沿晶斷裂方式過渡.由于 C 含量較少,該鋼的不可逆陷阱含量極少,大量的可擴散氫使得該鋼具有較高的氫脆敏感性.最后利用與Eshelby等效夾雜理論有關的氫致應力模型,驗證了應力集中與氫含量之間的變化關系.
0Cr16Ni5Mo steel is the most popular material used for fasteners and bolts in the marine engineering equipment. With the light weight trend of equipment, the strength grades of the steel become higher. 0Cr16Ni5Mo steel combines high strength, high hardness and high fracture toughness with good ductility. However, high strength steel is prone to degradation by hydrogen, resulting in the loss of its excellent mechanical properties. And the presence of diffusible hydrogen near a notch tip is easily to cause crack propagation. The susceptibility to hydrogen embrittlement of steel is largely determined by the hydrogen diffusivity and the behaviors of hydrogen trapping in the steel. Therefore, the hydrogen trapping behaviors of 1000 MPa 0Cr16Ni5Mo steel have been investigated by means of thermal desorption spectroscopy (TDS). Meanwhile, the hydrogen embrittlement susceptibility of the notch and smooth specimens was evaluated by slow strain rate tests (SSRT), and the fracture morphology was also observed. The results showed that the main hydrogen traps of experimental steel was contained dislocations and grain boundaries. The elongation of hydrogen charged specimens was decreased obviously rather than tensile strength. With the increase in hydrogen concentration, the fracture surfaces of hydrogen charged specimens was displayed a transition from ductile microvoid coalescence to a mixed morphology of dimples, quasi-cleavage and intergranular features. The steel had little irreversible hydrogen due to less carbon content, and had much susceptibility with reversible hydrogen contained. The model of hydrogen induced stress was calculated on basis of Eshelby equivalent inclusion, validating the relationship between stress concentration and hydrogen concentration.
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