Study On Corrosion Behavior Austenitic Steel For High Parameter Boiler On Flue Gas Side

The development of the Ultra-supercritical generating sets of,stringent requirements have been put forward for the performance of high-parameter boiler steels.In many boiler steel Super304H,HR3C two kinds of austenitic alloys with mechanical properties at room temperature,high temperature performance,chemical properties,technology performance,economy and other comprehensive performance in line with Ultra-supercritical boiler pipe requirements,become the main parameters of high pressure boiler pipe pressure parts?water wall,superheater,reheater?candidate matewial.The current research reports on high-parameter generator boiler tubes mainly focus on the evaluation and analysis of the mechanical properties and microstructure of the alloy materials.There are limited reports on the corrosion behavior of the alloys in the high-sulfur atmosphere/coal ash environment where power plants are actually operating.In this paper,The coal ash used in this experiment was taken as power plant boiler overheating pipe coal-as?X?Y coal ash?and laboratory synthetic coal ash.The SO₂ content in the simulate flue gas is 0.15%and 0.3%,At high temperature corrosion in 650?and 700?.The morphology and composition of the corrosion products were investigated by using XRD,SEM and EDS analysis,the corrosion behavior and corrosion mechanism of the synergistic effect of the atmosphere/coal ash of the experimental materials at different temperatures are discussed the advantages and disadvantages of the corrosion behavior of high temperature sulfur at the side of the two materials are compared.The corrosion processes of Super304H and HR3C alloys are similar at 650 and700°C,The initial high-temperature oxidation and the increase in sulfurization weight increase the kinetic curve.With the prolongation of the corrosion time,the increase of temperature,sulfate and metal oxides in the coal ash form a molten compound sulfate.Destruction and exfoliation of the product layer cause a decrease in the kinetic curve.Under the same corrosive environment,the corrosion resistance of HR3C steel against high temperature sulfur atmosphere/coal ash is superior to that of Super304H steel.The HR3C alloy is slightly corrosive to atmosphere/X coal ash and atmosphere/Y ash coal ash,which has good corrosion resistance;HR3C steel has a high content of Cr?25%?,The main products of corrosion in atmosphere/site coal ash?X coal ash and Y coal ash?are Fe₂O₃ and Cr₂O₃;In addition to the oxides,spinel compounds?NiFe₂O₄,CrFe₂O₄?and Fe₂?SO₄?₃ were also formed in the synthetic coal ash.Alloy at 650°C,0.15%SO₂ corrosion in the three coal ash environment less production,product layers are thin,With the increase of temperature and SO₂,the product layer of HR3C alloy in plutonium can be thicker than the X coal ash.In the synthetic coal ash environment,there was a noticeable peeling of the product.The content of Cr in Super304H is relatively low,and the corrosion products in atmosphere/source coal ash are mainly Fe₂O₃ and Fe₃O₄ at 650°C,and the main products at elevated temperature are Fe₂O₃ and?Cr,Fe?₂O₃;The alloy generates Fe₂O₃,Cr₂O₃,FeS,and spinel compounds?CuFe₂O₄,NiFe₂O₄,NiCr₂O₄?after etching at a temperature of 650°C to 700°C.in the atmosphere/X coal ash;the alloy removes iron,oxides of chromium,and sulfides in the coal ash.Sulfate?Fe₂?SO₄?₃?is also produced outside the plant.The SiO₂ and Al₂O₃ remained on the surface of the specimen after the corrosion of the coal ash on the two alloys.When the SO₂ concentration in the atmosphere increases from 0.15%to 0.3%,the oxides in the corrosion product of the alloy increase,and the oxides of Cr decrease.Super304H steel has good corrosion resistance in X coal ash environment;the corrosion product layer is thicker and delaminated in the Y coal ash,and some of the products are exfoliated;the corrosion is aggravated in the synthetic coal ash,the product is severely exfoliated,and the SO₂content The increase in the thermal corrosion of the low Cr alloy?Super304H steel?is more pronounced.In the same environment,the temperature rises from 650°C to700°C,and the loss per unit area of the sample increases by 2-3 times.In this experiment,the content of alkaline sulphates in the three types of coal ash was increased from the letter source coal ash,the plutonium energy coal ash,and the synthetic coal ash.due to the increase of alkali metal sulfate content in coal ash,the alloy's resistance to sulfate-type hot corrosion decreases.The experimental results show that the corrosion resistance of both Super304H and HR3C austenitic steels in the test environment are atmosphere/X coal ash better than atmosphere/Y caol ash can be better than atmosphere/synthetic ash.The corrosion of the alloy in the laboratory synthesis ash is the most serious.