1000MPa级0Cr16Ni5Mo钢的氢脆敏感性STUDY ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF 1000 MPa GRADE 0Cr16Ni5Mo STEEL

利用升温脱氢分析(TDS)实验研究了 1000 MPa 级 0Cr16Ni5Mo 马氏体不锈钢的氢陷阱行为.同时,采用慢应变速率拉伸实验(SSRT)研究了该钢缺口与光滑试样的氢脆敏感性,并利用SEM观察了试样的断口形貌.结果表明, 位错和晶界为该钢的主要氢陷阱,充氢后缺口试样与光滑试样的伸长率均下降明显,但强度变化不大.随着氢含量的升高,断口形貌由韧窝型韧性断裂向穿晶、准解理断裂,甚至向沿晶断裂方式过渡.由于 C 含量较少,该钢的不可逆陷阱含量极少,大量的可扩散氢使得该钢具有较高的氢脆敏感性.最后利用与Eshelby等效夹杂理论有关的氢致应力模型,验证了应力集中与氢含量之间的变化关系.
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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