简介：High-temperaturecorrosionisaseriousproblemforthewater-walltubesofboilersusedinthermalpowerplants.Oxidation,sulfidationandmoltensaltcorrosionaremaincorrosionways.Thereinto,themostseverecorrosionoccursinmoltensaltcorrosionenvironment.Materialsrichinoxidesformers,suchaschromiumandaluminum,areneededtoresistcorrosioninhigh-temperatureandcorrosiveenvironment,butprocessabilityofsuchbulkalloysisverylimited.Highvelocityelectricarcspraying(HVAS)technologyisadoptedtoproducecoatingswithhighcorrosionresistance.Bycomparison,NiCr(Ni-45Cr-4Ti)isrecommendedasapromisingalloycoatingforthewater-walltubes,whichcanevenresistmoltensaltcorrosionattack.Inthestudyofcorrosionmechanism,themodernmaterialanalysismethods,suchasscanningelectronmicroscopy(SEM),X-raydiffractometry(XRD)andenergydispersivespectrometry(EDS),areused.ItisfoundthatthecorrosionresistancesofNiCrandFeCrAIcoatingsaremuchbetterthanthatof20gsteel,thattheNiCrcoatingshavethebestanti-corrosionproperties,andthattheNiCrcoatingshaveslightlylowerporesthanFeCrAIcoatings.Itistestifiedthatcorrosionresistanceofcoatingsismainlydeterminedbychromiumcontent,andthemicrostructureofacoatingisasimportantasthechemicalcompositionofthematerial.Inaddition,thefracturemechanismsofcoatingsinthecycleofheatingandcoolingareputforward.Thedifferenceofthethermalphysicalpropertiesbetweencoatingsandbasemetalsresultsinthethermalstressinsidethecoatings.Consequently,thecoatingsspallfromthebasemetal.