| Incoloy 800H alloy has a wide range of applications in petrochemical industry,because of its excellent high temperature strength,high temperature oxidation resistance and corrosion resistance.However,the corrosive atmosphere in the service environment would often cause the corrosion of the alloy,with the alloy service conditions becoming increasingly complex,the corrosion resistance of the alloy presented a greater challenge."Grain boundary engineering?GBE?",the concept of grain boundary design and control,was proposed to optimize the grain boundary character distribution of the alloy,and to improve the grain boundary-related properties by the thermomechanical treatment process.The failure of Incoloy 800H alloy was mainly due to intergranular stress corrosion and intergranular corrosion.Therefore,grain boundary engineering treatment would be the most effective way to improve the grain boundary character distribution and corrosion properties of Incoloy 800H alloy.This paper was to design and control the grain size and grain boundary character distribution through cold rolling deformation and subsequent high temperature annealing,the effect of deformation,annealing process and iteration on grain boundary character distribution was studied,comparing the corrosion resistance,tensile and creep properties of the material.From this work,the following conclusions were drawn:?1?Based on the grain boundary character distribution and the improvement of intergranular corrosion tendency,the optimum thermomechanical treatment process for Incoloy 800H alloy was 15%cold rolling reduction followed by annealing at 1050? for 45min.?2?There underwent annealing twin production through the occurrence of recovery and recrystallization after thermomechanical process,the proportion of special grain boundary of Incoloy 800H alloy increased from 45.53%to 72.69%,and the connectivity of large angle grain boundary network had been interrupted.?3?Compared with the base material,the mechanical properties of the optimized sample were improved:the tensile strength increased by 6.7%in tensile test,the elongation increased by 11.3%;the creep properties of the material was improved in 600?/250MPa,the creep life increased from 251.9h to 405.8h and the creep strain rate reduced from 1.84×10-7 s-1 to 1.55×10-7 s-1.?4?The low-E CSL?coincidence site lattice,??29?grain boundaries have better intergranular corrosion resistance than large angle grain boundaries,and interrupted grain boundary network could inhibit the intergranular corrosion crack growth,so the intergranular corrosion resistance of the optimized alloy could be improved,the corrosion rate was reduced to 1/2 of the base material's. |
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