STUDY ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF 1000 MPa GRADE 0Cr16Ni5Mo STEEL

Abstract

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 grade 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, quasicleavage and intergranular features. The steel had little irreversible hydrogen due to less C content, and had much susceptibility with reversible hydrogen contained. The model of hydrogen induced stress was calculated on basis of *收到初稿日期: 2015-01-12,收到修改稿日期: 2015-05-16 作者简介:孙永伟,男, 1986年生,博士生 DOI: 10.11900/0412.1961.2015.00033 第1315-1324页 pp.1315-1324