鋼的低溫復合滲鉻層的微觀組織與結構表征.pdf

1、湖南大學碩士學位論文鋼的低溫復合滲鉻層的微觀組織與結構表征姓名：元敏申請學位級別：碩士專業(yè)：材料物理與化學指導教師：伍翠蘭20100414鋼的低溫復合滲鉻層的微觀組織’j占構表征AbstractLowtemperaturecompositechromizingisthetwo—stepprocess，whichis6rstnitridingornitrocarburizingat540℃～580℃andf0110wingchromizi

2、nginasaltbathbelow700℃Inthispaper，themicrostructure，thedistributionoftheCrandN，thecrystallineofphasesandthemorphologyofnitridesorcarbidesinconlpositechromizedlayers，whichhadfomedduringlowtemperaturecompositechromizing，we

3、reinvestigatedusingX—raydiffractometer’opticalmicroscopy’scanningelectronmicroscopy，transmissionelectronmiCroscopyInordertodecreasethechromizingtemperatureandimproVethequalityofchromized1ayer，theprocessingparameters，such

4、astheingredientsofsaltbath，werestudiedTheresultsshowthatthemainphasesinthelow—temperaturechromizedlayersareCrN，p，Q一(Cr，F(xiàn)e)andCr7C3Whenthechromiumatomsfromthesaltbathdiffuseintothesurfaceofsampleandthencombinewiththenitro

5、genatomsinoriginalnitridedconlpoundslayer，thechromizedlayerisgraduallyfbmedTheamountofnitrogeninoriginalnitridedlayerplaysaninlportantroleinthequalityandthicknessofchromizedlayerandthecaIbonofthesubstratewasnosignificant

6、contributiontoincreasethethicknessofchromizedlayerat500℃Thenitrogenatomsoforiginalnitridedlayerhadtwoactionsinthechromizingprocess：ontheonehand，theycombinewiththeactivechromiumatomsinthesurfacelayertofomchromizedlayer；on

7、theotherhand，theydiffuseintotheinsideofthespecimen，resultingintheineffectivelossAtthelowertemperature，thediffusionrateofnitrogenatomisVeryslow，asreducethelossoftheinef億ctiveloss，soitishelpfultoincreasethethicknessofchrom

8、izedlayerThechromiumcarbidesintheouterlayerarefomedwhenthechromiumatomsonthesurfacecombinewiththecarbonatomsfromthesubstrateaftertheconsumingofnitrogenatomsoftheoriginalnitride1ayerOwingtotheconcentrationofchemicalcompos

9、itionandthemodynamiceffect，CrNwillbeformedpriortopphaseWhenthechemicalpotentialofnitrogeninthesamplesurfaceisdecreasedtoacertainextent，thenitrogenatomscancombinewiththechromiumatomstofompWithincreasingoftemperatureandthe

10、concentrationofcarboninthematrix，theconcentrationofCrNphaseisgraduallyincreasingwhilethatofa—phaseisgraduallydecreasingTherearesomesubmicronCINclusteredareasandnanocrystallineCrNclusteredareasinthelow_temperaturecomposit