Activated gas nitriding of 17-4 PH stainless steel

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1、Surface&CoatingsTechnology200(2006)6558–6562www.elsevier.com/locate/surfcoatActivatedgasnitridingof17-4PHstainlesssteelP.Kochmański,J.Nowacki⁎TechnicalUniversityofSzczecin,Al.Piastow17,70-310Szczecin,PolandAvailableonline15December2005AbstractResultsoftheinvestigationofnitride

2、dprecipitation-hardenedsteel17-4PHsurfacehavebeenpresented.Thelayershavebeencreatedasaresultofthegasnitridingprocessinapartlydissociatedammonia.Hydrogenchlorideadmixturetoammoniawasusedasasteelsurfaceactivator.Theinfluenceofthesteelheattreatmentbeforenitridingonthediffusivepro

3、cesshasbeenconsidered.17-4PHstainlesssteelinvariousstatesofheattreatment,i.e.insupersaturatedorprecipitation-hardenedstatewasnitrided.Thenitridedlayerswerestudiedbyscanningelectronmicroscopy,X-raymicroanalysis(EDXandWDX),andX-raydiffraction.MicrohardnesstestsofthelayersusingVi

4、ckersmethodhasbeendonetoo.Hardnessofthegeneratedlayersreached1700HV.Theoptimaltemperaturerangeofthethermo-chemicaltreatmentwasdetermined.Theinfluenceofprecipitationprocessestakingplaceduringtheheattreatmentbeforenitridingonkineticsofdiffusivenitridingprocess,surfacegeometryand

5、thecreatedlayerpropertieshasbeenproved.Thetestsresultsshowed,thatnitridedlayersthicknessisbiggeronabaseofthe17-4PHstainlesssteelinprecipitation-hardened,thaninsupersaturatedstate.Increaseofsteelageingtemperaturebeforenitridingcausedanincreaseofthenitridingprocessintensity.Diff

6、erencesofsurfacemorphology,thickness,phasecompositionandnitrogenconcentrationofthediffusionlayerscreatedatthesamenitridingconditions,butvariousconditionsof17-4PHsteelheattreatmentbeforenitridinghavebeenobserved.©2005ElsevierB.V.Allrightsreserved.Keywords:Precipitation-hardenin

7、gstainlesssteel;17-4PHsteel;Gasnitriding1.IntroductionstrengthRm=900–1400MPa,yieldpointRe=590–1280MPa,impactresistanceKV=20–135Jandhardness27–44HRC.Precipitation-hardenedstainlesssteel17-4PHiswidelyusedThehighestvaluesofstrengthandhardnesscorrespondwiththeasstructuralmaterialb

8、ecauseofitsbalancedcombinationoflowestageingtemperaturesdueto