Stress corrosion cracking and hydrogen embrittlement behavior of titanium-based materials:a review
Due to the combination of excellent specific strength,good corrosion resistance,heat resistance,and bio-logical compatibility,titanium and its alloy have played a vital role as one of the most important materials candi-dates used in the high-end manufacturing,including aerospace,nuclear industry,petrochemical industry as well as biomedical devices.While the further development and application of titanium-based materials are significantly re-stricted by the stress corrosion cracking(SCC)/hydrogen embrittlement(HE)and limited working process window.Moreover,the SCC and HE behavior poses a major threat to the service safety and life extension of the titanium-based components.In attacking service environment,titanium-based structural materials commonly suffer from the stress corrosion cracking,especially the hot salt stress corrosion cracking(HSSCC),salt aqueous stress corrosion cracking,and hydrogen-induced brittle fracture.The presence of moisture and oxygen favors the reactions between the protective oxide layer of titanium and the salts,thus accelerates the corrosion of titanium matrix and generation of corrosion products(titanium chlorides and atomic hydrogen).It is proposed that the cathodic hydrogen evolution reaction(HER)dominates the hydrogen embrittlement behavior of titanium-based materials via affecting the pas-sivation of titanium oxide films.To be specific,the electronic structure of the oxide films is altered by the hydrogen atoms.The compactness and stability of protective films are resultantly weakened.Except for the strength and duc-tility,hydrogen also exerts great impact on the fatigue performance of titanium-based materials.Interestingly,high-er hydrogen content may prolong the fatigue life of titanium alloys.A hydrogen-induced time-dependent load shed-ding inside the lamellar microstructure and localized plasticity at the crack tips synergistically increase the dwell-fa-tigue life of Ti-6242Si alloy.While the formation of brittle titanium hydrides at phase boundaries is responsible for the severe ductility and toughness loss.Advanced surface treatment,like laser shock peening(LSP),is regarded as a promising process to reduce the HE susceptibility of materials.The compressive residual stress layer produced by LSP leads to the near-surface grain refinement,reduction of hydrogen solubility,and density increment of effective hydrogen trapping sites,such as twins and dislocation tangles.Therefore,the uptake of hydrogen of titanium alloys can be effectively retarded.While the post printing heat treatment deteriorates the HE resistance of TC4 alloy print-ed by laser beam powder bed fusion(LB-PBF),which can be ascribed to the introduction of β phase with high hy-drogen solubility and the preferential nucleation of cracks at the brittle hydrides in the α/β phase interface.Additive manufacturing(AM)might be an accessible technical pathway to reduce the HE susceptibility of titanium-based al-loys owing to the grain refinement and variation of dislocation substructure in the as-printed materials.Besides,AM technology also provides a promising way to improve the processing efficiency of titanium-based structural materials.Eventually,it is pointed out that the focus of the future development of titanium-based materials should be placed on the following aspects:additive manufacturing processes;further improving the corrosion and stress corrosion resistance through stabilizing the protective oxide film and elucidating the underlying mechanisms of the formation of corrosion products,titanium hydrides,and the interaction between hydrogen and substructures of tita-nium-based materials.
NETL
NSTL
万方数据
