THERMODYNAMIC AND KINETIC MODELING OF PRECIPITATION PHENOMENA IN P9 STEELS

Proceedings of ASME Turbo Expo 2011

GT2011

THERMODYNAMICANDKINETICMODELINGOFPRECIPITATIONPHENOMENAINP9STEELS

K.C.HariKumar V.B.Rajkumar

DepartmentofMetallurgicalandMaterialsEngineering

IndianInstitueofTechonlogyMadras

Chennai600036,INDIAEmail:kchkumar@iitm.ac.in

S.Raju

PhysicalMetallurgyDivision

IndiraGandhiCentreforAtomicResearch

Kalpakkam603102,INDIA

ABSTRACT

Thermo-kineticsimulationofprecipitateevolutionduringlong-termthermalexposureinfourdifferentferritic-martensiticheat-resistantpowerplantsteels(P91,P92,E9016,andRAFM)iscarriedoutusingMatCalcandThermo-Calcsoftwares,incom-binationwithanindependentlydevelopedGibbsenergydatabaseandamodi edversionofmobilitydatabaseforsteelsthatcomeswithMatCalc.MXandM23C6arepredictedtoremainasma-jorprecipitatesduringlong-termaginginthesesteels.AveragesizeofMXprecipitateisfoundtovarybetween10-100nmdur-ingtheaging,whileM23C6exceeds100nmafter100,000hofthermalexposureat600 C.Thesimulatedprecipitationsequenceandprecipitatesizeevolutionduringthermalexposureareingen-eralagreementwithavailableexperimentaldata.Itisexpectedthatthecalculationspresentedheregivesinsightintolong-termmicrostructuralstabilityofferritic-martensiticsteelsunderser-viceconditions,whichareotherwisedif cultestablishbyexper-imentsalone.

Introduction

Thereisanurgentneedtoimprovethethermalef ciencyoffossilfuelaswellasnuclearpowerplants,mainlyduetoen-vironmentalconsiderations.Thiscanbeachievedbyincreasingoperatingtemperatureandpressureofthepowerplants.Inthis

contextpipematerialsthatcanperformwellatelevatedtempera-tureandpressurearedesirable,withoutcompromisingsafetyas-pects.Plantoperationsathighertemperaturesinevitablyrequiresthedevelopmentofheat-resistantalloyswithahighercreeprup-turestrengthatanacceptablelevelofcreepductility.Inthisre-gard9-12%Crferritic-martensiticheatresistantsteelswithotheralloyingadditionsareidealmaterialsowingtotheirhighthermalconductivity,lowthermalexpansioncoef cientandlowsuscep-tibilitytothermalfatigue.

Itisgenerallyacceptedthatferriticandausteniticsteelsareusefuluptoabout620and675 C,respectively,purelyfromthecreepstrengthpointofviewatasteampressureofabout35MPa[1].Theroleofprecipitationphenomenoninenhancingcreepstrengthofheat-resistantsteelsiswellestablished[2].Inordertoimprovethecreepstrengthitisnecessarytoensureauni-formdistribution neprecipitateswithgoodlong-termhightem-peraturestability.Forexample,austeniticheat-resistantsteelsareknowntoexhibitquitecomplexprecipitationbehaviorin-volvingprecipitatessuchascarbides,nitridesandintermetallicphases[3].Inthecaseof9-12%Crferritic-martensiticsteels,thecreepstrengthisduetotheirspecialmicrostructuralfea-tures.Duetodiffusionprocessesatelevatedtemperatureser-vice,microstructuralchangestakesplaceleadingtodeteriorationinstrength.Inferritic-martensiticsteelsstrengthdeteriorationisattributedtocoarseningofM23C6precipitatesandtransfor-mationofMXprecipitatesintoZ-phase(Cr(V,Nb,Ta)N).Inthis Address

allcorrespondencetothisauthor.

搜索“diyifanwen.net”或“第一范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，第一范文网，提供最新资格考试认证THERMODYNAMIC AND KINETIC MODELING OF PRECIPITATION PHENOMENA IN P9 STEELS全文阅读和word下载服务。