Effect Of Pre-Deformation On Aging Behavior And Intergranular Corrosion Property Of SUPER304H Stainless Steel

SUPER304H austenitic stainless steel have been used for the tube of ultra-supercritical Boiler's superheater because of its good resistance to general corrosion and weld property.Because its work environment is so terrible,however,the microstructure after aging for different time and its intergranular corrosion susceptibility should be deeply studied.Precipitation and intergranular corrosion susceptibility of SUPER304H austenitic stainless steel aged for different time on 700℃have been studied in this paper.Microstructure of samples deformed 0,15%and 20%before aging were studied by TEM and extraction replica.The precipitation were identified by combining electron diffraction and X-ray spectrum.Degree of intergranular corrosion susceptibility was evaluated by DL-EPR in 0.5MH₂SO₄+0.01MKSCN solution.The main conclusions were report below:Precipitation content was increased with the aging time.M₂₃C₆ type carbide precipitated at grain boundaries and innergranular,besides,face-center cube NbC was found within grains. Influence of deformation on microstructure was that there were a lot of precipitation of NbC with profile of sphere,needle,quadrangle and hexagon.Reaction rate(Rr)which was obtained by DL-EPR testing of all samples showed a trend that increased and then decreased with aging time going.Samples deformed before aging had the highest Rr when they were aged for 100h,which was earlier than that of un-deformed samples which had its highest Rr when they were aged for 1000h.Rr of samples which were deformed was higher than that of samples which were un-deformed.Rr of 15%-deformation samples were higher than that of 20%-deformation samples.