455
5
Vol.45
No.5
2009
566—572ACTAMETALLURGICASINICAMay2009pp.566–572
0Cr18Ni9
∗
(
,
710048)
,
SFPB:
(SFPB)
0Cr18Ni9
,
.
SFPB
,
250µm
,
,
15nm,,
,
,
.
SFPB
450
,
,
,
.,
,
,
,
.
0Cr18Ni9
,
,
TG142.71,TG156.8
A
0412−1961(2009)05−0566−07
EFFECTOFSURFACENANOCRYSTALLIZATIONAND
THERMALSTABILITYOF0Cr18Ni9STAINLESSSTEELONLOWTEMPERATURENITRIDINGBEHAVIOR
GELiling,LUZhengxin,JINGXiaotian,LIUZhongliang,TIANNa
SchoolofMaterialsScience&Engineering,Xi’anUniversityofTechnology,Xi’an710048
Correspondent:GELiling,seniorengineer,Tel:(029)82312536,E-mail:geliling–xut@163.comManuscriptreceived2008–04–24,inrevisedform2008–09–18
SupportedbyNationalNaturalScienceFoundationofShaanxiProvince(No.2005E101)
ABSTRACTThecompositestructurewithananocrystallizedsurfaceandthematrixisveryusefultoobtaingoodcomprehensiveproperties.Surfacenanocrystallizationisanimportantwaytomakeagoodcombinationofhighhardnessonthesurfaceandgoodductilityatthecenterofmaterials,whichnotonlymodifiesthesurfacialproperties,butalsoprovidesmorechannelstoaccelerateatomstodiffuse.Inthiswork,ananostructuredlayerwasfabricatedona0Cr18Ni9stainlesssteelsheetsurfacebyasupersonicfineparticlebombarding(SFPB)technique,andfollowedbylowtemperaturegasnitriding.Theeffectofthenanocrystallizationonthesurfaceofthe0Cr18Ni9stainlesssteelonthermalstabilityandthegasnitridingatlowtemperaturewasinvestigatedbymetallograph,XRD,TEMandmicroscopichardness.Itisfoundthatadeformationzonewithadepthofabout250μmisformedonthesurfaceafterSFPBtreatment.Thesurfacemicrostructureiscomposedofnanocrystalswithanaveragegrainsizeof15nm.Itisalsofoundthattwinningdominantlycontrolssurfacedeformation.Meanwhile,thereismartensitetransformationonthesurfaceduringthedeformation,thusresultinginasignificantincreaseofsurfacehardness.Afternitridingat450,theSFPBtreatedspecimenshowsanexcellentthermalstabilitywithastablehardnesseventhoughnoobviouslycoarseningofnanocrys-talonthesurfacelayerandaslightdecreaseoftheamountofmartensites.IncomparisonwiththespecimenwithoutSFPBtreatment,grainrefinement,martensitetransformationandexcellentther-malstabilityarethemainreasonsfavorableforrapidnitridingatlowtemperature,whichcontributeto
*
2005E101
:2008–04–24,
:2008–09–18
:
,
,1961
,
5
:0Cr18Ni9
567
thethickernitridinglayer,thefurtherincreaseofsurfacehardnessandtheimprovementofhardnessgradient.
KEYWORDS0Cr18Ni9stainlesssteel,surfacenanocrystallization,thermalstability,
lowtemperaturegasnitriding
,
,
,
.
,
,
,
[1−5]
.
.
,.
(supersonicfine
particlesbombarding,SFPB)
–
,,
,
,
,
,
[6,7]
.
,
0Cr18Ni9
,
.
300,400
450
,
2.
,
[8]
,
,
,
,
.
,
.
,
0Cr18Ni9
SFPB
(
),
[9,10]
,.
1
0Cr18Ni9
,
,50μm.(,%):C0.049,Cr18.24,Ni8.22,Si≤1.00,Mn≤2.00,S≤0.030,
P≤0.035,Fe.
60mm×
60mm×4mm
,
,
SFPB
,
.
1433/8558Pro-GREssive(DT1480)
,
,
,
SFPB
.
:
0.18MPa;
0.3mm
;
85◦;
15,3060min.5,SFPB
30min
,300,350,400
450
9h
,
,
;
300,400
4509h
,
,
560
,
,[11]
,
.
GX71
XRD–7000S
X
(XRD)JEM–3010(TEM)Tukon2100B/
SFPB
,
0.5N,
10s.TEM
,
,
30μm,
MTP–1A
,
.
22.1
SFPB
0Cr18Ni9
SFPB
,
,
,
30min,
250μm,
1.
,
.
,
30μm
,
,
.
30—250μm
,
(
)
,
1
30minSFPB
Fig.1Cross–sectionopticalmicrostructureofthesurface
layerof0Cr18Ni9stainlesssteelsampleafterSFPBtreatmentfor30min
568
45
2
.
0Cr18Ni9
[3]
SFPB,
SFPB
5min
,
SFPB
XRD
.
,
,
,
,
,K
39.9%,43.3%,47.5%
49.2%.
,
SFPB
Bragg
,
,
.5,15,3048.1,25.7,15.4
[3]
60min12.5nm.,
SFPB
,
,
30min
.
3TEM
SFPB
30min
(SAED).
2SFPB
XRD
,
,
15nm
Fig.2XRDpatternsofthestainlesssteelsurfacebefore
andafterSFPBtreatmentfordifferenttimes
(
3a).
30μm
TEM
,
,
,
60nm,
3SFPB30minTEM
Fig.3TEMimagesandcorrespondingSAEDpatternsatdifferentdepthsfromthesurfaceofsample
afterSFPBfor30min
(a)surfacelayerconsistingofmartensite
(b)martensiteandaustenitecoexistingatabout30µmindepth(c)austenitewithdeformationtwinningatabout60µmindepth(d)dislocationreactionatabout200µmindepth
5
:0Cr18Ni9
569
SAED
,(
3b).
60μm
,
,
,
(
3c).
,
,
.
200μm,
(4d).
0Cr18Ni9
2(16.8mJ/m),
,
,
,
[4]
.
2.2SFPB
4
0Cr18Ni9
SFPB
.
,
,
30min(HV650),HV
250.
SFPB
.
5SFPB
30min
.
,
SFPB
30μm
,,
;
4
SFPB
Fig.4SurfacemicrohardenssofsamplesvsSFPBtreat-menttime
530minSFPB
Fig.5Hardnessvariationalongdepthofthesamplesbefore
andafterSFPBtreatmentfor30min
30—60μm
,
,
,
;
60—120μm
,
,
;
120—250μm
,
,
.
30—250μm
,
,
30—
120μm
,
120—250μm
[3,4]
.2.3SFPB
6SFPB
30min
400450
9h
.
,
,
60μm
,
,
,
.
XRD
(
7)
,SFPB
.
,2.
300,350,
400450,
45.2%,45.0%,
43.9%
39.9%,,
6SFPB
Fig.6HardnessdistributionsoforiginalandSFPBsampleswithoutandwithheattreatment
7SFPB
XRD
Fig.7XRDpatternsofthesurfacelayerof0Cr18Ni9stain-lesssteelafterannealedatdifferenttemperaturesaf-terSFPBtreatmentfor30min
570
45
.,
,
,
;400
SFPB
19.8,21.7,23.527.7nm.
0Cr18Ni9SFPB450
15—20μm
90μm,
,
5—10μm
.
,
;450
(
)
25—30μm
,
SFPB110μm,
,
15μm,
[12]
.
,
SFPB
.0Cr18Ni9
2.4Ni9
,
.300
SFPB
30min
300,400
SFPB450
0Cr18-9h
SFPB
,
,
,
8
.
300
.
,
SFPB
,
SFPB
,
,
5μm
30μm
,
,
80Cr18Ni9SFPB39h
Fig.8Cross–sectionopticalmicrostructuresof0Cr18Ni9stainlesssteelnidridizedafterandbeforeSFPBtreatment
atdifferenttemperaturesfor9h
5
:0Cr18Ni9
571
;
,
(
),
<6μm,30
,
.
,
60μm.
0Cr18Ni9
SFPB
0Cr18Ni9
,
.
,
,
,
,
,
SFPB
300,
γ
ε.
,
.,
SFPB
,
.
,
SFPB
300
,
300
,
,
,
.
,
,
.
9
SFPB
450
9h
XRD.
FeN(α)
,
Fe4N(γ)
Fe3N(ε).
,Fe
FeN,.
,
,
,
,
SFPB
,,
,
,
γε
,
SFPB
[13]
.
10SFPB
30min
SFPB
300,400
450
9h
.
,
,,
SFPB300,
400
450
HV
700,1450
1478,
3
.
,
SFPB
(
SFPB)
30,90110μm;
SFPB
9SFPB
450
9h
XRD
Fig.9XRDpatternofaSFPBsamplesurfaceafternitrid-ingat450
for9h,
,
,
,
10SFPB
Fig.10Microhardnessdistributionsalongdepthofthesur-facelayerofSFPBandoriginalsamplesnitridizedat
300(a),400(b)and450
(c)for9h57245
,
,
,
.
3
(1)0Cr18Ni9SFPB
250μm
,
15nm
,
,
.
.
(2)SFPB
,,
.
,
.
(3)SFPBSFPB,
450.
,
,
.
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