Mechanism Research Of Composite Ceramic Coatings Prevent Corrosion And Affection Of Boiler Operation Parameters

Because of the coal's poor quality,the tube explosion phenomenon of boiler heating surface is quite serious in our country.High temperature corrosion of heating surface is an important reason of tube explosion.Aiming at the problem,this paper use thermochemical reaction method prepare Si₃N₄/BN multiphase ceramic coatings on the surface of 20 G,15CrMoG and TP347.Then prove the corrosion resistance of Si₃N₄/BN multiphase ceramic coatings by corrosion test.At the same time,prepare the multiphase ceramic coatings on the heating surface of utility boiler.Then uses the thermodynamic calculation solve some issues of boiler operation caused by multiphase ceramic coatings.Firstly,morphology analysis of surface and interface of Si₃N₄/BN multiphase ceramic coatings were investigated by scanning electron microscopy?SEM?.The results show that,the powder particles on the surface of coatings are compact and well distributed.The binding situation of coatings and metal matrix is good,and there is no defect in binding domain,such as hole,gap and crack.So the coatings can prevent the corrosive away from metal matrix.Then,starting the corrosion test.The test has been divided into three parts,SO₂ gas corrosion,H₂ S gas corrosion and sulfate corrosion.The result of SO₂ gas corrosion test shows that,the corrosion resistance of multiphase ceramic coatings on the surface of 20 G,15CrMoG and TP347 improved 5.39 times,6.53 times and 2.28 times than 20 G bases,15 CrMoG bases and TP347 bases.The result of H₂ S gas corrosion test shows that,the corrosion resistance of multiphase ceramic coatings on the surface of 20 G,15CrMoG and TP347 improved 9.59 times,2.69 times and 3.82 times than 20 G bases,15 CrMoG bases and TP347 bases.The result of sulfate corrosion test shows that,the corrosion resistance of multiphase ceramic coatings on the surface of 20 G,15CrMoG and TP347 improved 1.73 times,1.49 times and 1.54 times than 20 G bases,15 CrMoG bases and TP347 bases.Finally,using the Si₃N₄/BN multiphase ceramic coatings in field.The calculation result shows that,lower temperature of main steam casued by unreasonable spraying proportion of coatings,when the coatings cover all of wall superheater,the main steam temperature can meet the boiler operation requirments.Calculating by change the spray proportion of multiphase ceramic coatings and the hight of flame center.The results show that,when amplify the spray proportion of multiphase ceramic coatings of furnace,the gas temperature of furnace outlet and attemperation water will be decreased greatly.We know that condition of spray all the wall superheater is the best scheme.