research article composition design and fatigue...

Research ArticleComposition Design and Fatigue Curves ofHardfacing Materials for Cold Roll

C L Chen12 C X Chen12 Z H Guo1 J Ding12 X Han1 and Q Jiang1

1School of Materials Science and Engineering Hebei University of Technology Tianjin 300132 China2Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology Tianjin 300132 China

Correspondence should be addressed to C X Chen karenccx126com

Received 30 November 2015 Revised 4 February 2016 Accepted 7 February 2016

Academic Editor Sheng-Rui Jian

Copyright copy 2016 C L Chen et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In order to improve the fatigue life of cold rolls a series of hardfacing alloys were designed by orthogonal experiments consideringthe interaction between carbon chromium and niobium Hardfacing layers were produced by Tungsten Inert Gas (TIG) arcwelding The effects of alloy content on microstructure and carbides and fatigue behavior at different load frequency and differenttemperature were analyzedThe results show that suitable combination of 05 C 40 Cr and 20Nb can obtain a high hardnessof 547 HRC for the formation of fine lath martensite and carbides with dispersed distribution The new designed hardfacingmaterials have similar Δ120576-119873 curves with parent material in low load frequency and below 400∘C

1 Introduction

Thewidely used backup rolls in industrial production alwaysendure cycle load at high temperature during rolling process[1] Therefore subsurface cracks can form for the contactfatigue and then propagate to surface resulting in spalling [23] In order to improve the mechanical properties of roll sur-face and avoidmaterial waste for the replacement of new rollsoverlaying welding is usually used to develop surface layerswhich make considerable contributions to high productivityhigh product quality extended roll life and low material cost[4 5]

Hardfacing should be a material selected for high hard-ness and goodmicrostructural and for strength and economy[6]There are many kinds of hardfacing alloy systems includ-ing cobalt-based nickel-based copper-based and iron-basedalloys Fe-based alloys are considered as one of the mostpromising alloys for their high bonding strength high hard-ness excellent mechanical properties and lower cost thancobalt-based and nickel-based overlaying so it has drawnmore and more attention in recent years [7]

Carbides such as chromium carbide and tungsten car-bide are very important strengthening phases in hardfacing

layer and used widely in hardfacing materials However thehardfacing layer must have higher fatigue resistance to avoidspalling failure which requires that hardfacing layer musthave a good match of hardness and toughness So multialloysystem is adopted to solve this problem Except chromiumand tungsten strong carbide forming alloy elements such asniobium and titanium are added in hardfacing materials togain hardMC type carbides As one of themost effective hardparticles MC carbides are sphere and short rods in shape andthe hardness is up to 2000sim3000HV which will strengthenthe hardfacing layer Moreover the carbides of niobium andtitanium can effectively refine microstructure by pinninggrain boundary [7ndash9] and be helpful for the improvement oftoughness [10]

The purpose of this research is to control the type andquantity of carbides and predict fatigue curves of rolls underthe condition of high temperature and different load fre-quency New hardfacing materials with different contentmatch of carbon chromium and niobium were developedwith goodmatch of strength and toughness In addition loadfrequency and temperature effects on hardfacing materialwere investigated compared with 9Cr2Mo

Hindawi Publishing CorporationJournal of EngineeringVolume 2016 Article ID 8487976 5 pageshttpdxdoiorg10115520168487976

2 Journal of Engineering

Table 1 Chemical composition of hardfacing materials (wt)

C Si Mn Cr Mo W + V + Ti Nb Fe03ndash05 05 15 30ndash50 le20 le21 20ndash60 Bal

2 Experiment and Calculation Method

21 Experimental Procedure Three factors and three-levelorthogonal experiments were adopted to design the hardfac-ing materials The interactions between carbon chromiumand niobium were considered in this study The compositionof hardfacing material is shown in Table 1

The hardfacing materials were deposited on low carbonsteel using the Tungsten Inert Gas Welding Technology Inorder to gain undiluted layer the thickness of hardfacing lay-ers was approximately 8mm

The hardness was tested by Rockwell hardness testingmachine All specimens were etched with a solution of4 nital Microstructure examination of the specimens wascarried out by Olycia M3 optical microscopy (OM) and NovaNano SEM450s scanning electronmicroscopy XPertMPDX-ray diffractometer was used to analyze carbides

22 Fatigue Curves Calculation The 119878-119873 relationship ofmaterials can be obtained using fatigue test [11] However a lotofmoney and timewill be spent So calculating fatigue curveshas great advantages JMatPro a multiplatform software pro-gram for the prediction of the properties of multicomponentalloys was used to analyze the fatigue property (Δ120576-119873 curves)of hardfacing materials

In this method a relationship between monotonic tensileproperties and uniaxial fatigue properties was developed firstand then combined high temperature properties (Youngrsquosmodulus and strength) to evaluate the fatigue curves of thematerial The relationship between the strain range Δ120576 andsubsequent fatigue life 119873 is usually given by the classicalCoffin-Manson Equation

Δ120576

2=Δ120576119890

2+

Δ120576119901

2=Δ120590

2119864+ (Δ120590

21198701015840

)

1119899

1015840

Δ120576

2=Δ120576119890

2+

Δ120576119901

2=

1205901015840

119891

119864(2119873)119887

+ 1205761015840

119891

(2119873)119888

(1)

in which Δ120576 is total strain range in axial fatigue test Δ120576119890is

elastic strain range in axial fatigue test Δ120576119901is plastic strain

range in axial fatigue test 119873 is number of cycles to failure1205901015840

119891

is axial fatigue strength coefficient 1205761015840119891

is axial fatigueductility coefficient 119887 is axial fatigue strength exponent 119888 isaxial fatigue ductility exponent 1198991015840 is cyclic strain hardeningexponent1198701015840 is cyclic strain hardening coefficient

The two equations are usually used to describe the cyclicstress-strain behavior and strain-life relationship [12]

3 Results

31 Hardness Table 2 and Figure 1 give the hardness resultsof orthogonal experiments It can be seen that carbon is

Table 2 Hardness of different samples

C (wt) Cr (wt) Nb (wt) Hardness (HRC)1 03 30 20 4232 03 40 40 683 03 50 60 1454 04 30 40 4005 04 40 60 826 04 50 20 5007 05 30 60 4198 05 40 20 5479 05 50 40 5041198791119895

636 1242 1471198792119895

982 697 9721198793119895

147 1149 6461198721119895

212 414 491198722119895

3273 2323 3241198723119895

49 383 2153119877119895

278 1817 2747

20

25

30

35

40

45

50

Har

dnes

s (H

RC)

Nb2 Nb3Nb1Cr2 Cr3Cr1C2 C3C1Factor

Figure 1 Relationship between hardness and factors

the most effective factor for the hardfacing hardness and theleast is chromium Moreover the hardness is improved withthe increasing of carbon content and the decrease of niobiumcontent However the hardness exhibited a drop and then risewith the increase of chromium content This is related to thecarbon redistribution and carbides content [4] As a strongcarbide forming element niobium carbides will precipitatefirst at high temperature stage The higher the niobiumcontent is the lower the content of carbon in matrix andchromium carbides is and the lower the hardness is Accord-ing to the thermodynamic equilibrium calculation the aver-age mass fraction of NbC is 388 331 and 345 in thelevel of 30 Cr 40 Cr and 50 Cr respectively As NbChas significant effect on hardness the hardness exhibited adrop and then rise with the increasing chromium contentThrough the analysis of Figure 1 05 C 30 Cr and 20

Journal of Engineering 3

2 3 4 5 6 71 98

Number of each experiment

0

1

2

3

4

5

6

Mas

s fra

ctio

n of

carb

ides

(wt

)

Figure 2 Mass fraction of carbides

20120583m

(a)

20120583m

(b)

Figure 3 Microstructure of hardfacing layer of (a) alloy 2 and (b) alloy 8

Nb appear to be an optimum composition for the improvedRockwell hardness

Table 2 also shows that hardness changes evidently for thesamples with different content match of carbon chromiumand niobium This contributes to carbides type and content(as shown in Figure 2) Under the condition of certain carboncontent the ratio of CrNb is very important to the hardnessFor alloy 1 with higher CrNb ratio 15 the hardness is 423HRC But the hardness decreases evidently for alloys 2 and 3with lower CrNb ratio The same phenomenon can be seenfor samples with carbon content of 04 and 05 Alloy 8with 05 C and 20 CrNb ratio has the highest hardness forits higher carbides content It indicates that the goodmatch ofC Cr and Nb is crucial to achieve a hard matrix with a largefraction of carbides

For the same chromiumcontent the interactions betweencarbon and niobium influence the hardness dramaticallyThehardness of alloy 2 and alloy 8 with 40 Cr is 68 HRCand 547 HRC respectively for the different content of Cand Nb The microstructure of alloy 2 is composed of ferriteand carbides for the low carbon content and higher niobiumcontent as shown in Figure 3(a) The carbides mainly consist

of NbC and TiC (as shown in Figure 5(a)) and are distributedin grain boundary (as shown in Figure 4(a)) This is becauseniobium is the element to reduce the 120574 phase which is helpfulfor the formation of ferrite In addition as a strong carbideforming element [7] NbCwill precipitate first and inhibit theformation of chromium carbides

For alloy 8 with higher carbon content and lower nio-bium the microstructure is composed of fine lath martensiteand dispersed carbides (NbC and Cr7C3) (as shown in Fig-ures 3(b) 4(b) and 5(b)) which contributed to the excellenthardness [4]

32 Δ120576-119873 Curves Considering the service environment ofcold rolls load frequency and temperature have great effecton fatigue performance In order to evaluate the fatigue lifeof new designed hardfacing materials (05 C 30 Cr and20 Nb) a series of Δ120576-119873 curves at high temperature werecalculated compared to 9Cr2Mo

Figure 6 gives the Δ120576-119873 curves of alloy 9Cr2Mo and theoptimum new alloy in different load frequency at 400∘C Itcan be seen that when the load frequency is 1 Hz the fatigue


20120583m

NbC

(a)

20120583m

NbC

(b)

Figure 4 Carbides distribution (a) alloy 2 and (b) alloy 8

(Ti Nb)C

8020 40 60

2120579 (deg)

0

2000

4000

6000

8000

10000

12000

Inte

nsity

(cps

)

120572-Fe

(a)

M7C3(Ti Nb)C

8020 40 60

2120579 (deg)

1000

1500

2000

2500

3000

3500

4000

Inte

nsity

(cps

)

120572-Fe

(b)

Figure 5 XRD results (a) alloy 2 and (b) alloy 8

1

10

Tota

l str

ain

()

100 1000 10000 100000 1000000 1E710

Number of cycles

9Cr2Mo 1Hz9Cr2Mo 200Hz

10 1Hz10 200Hz

Figure 6Δ120576-119873 curves of alloy 9Cr2Mo and the optimumalloy (10)under different load frequency at 400∘C

curves of the two alloys are similar which indicates that thehardfacing material (the optimum alloy) has the same fatigueproperties with the roller matrix (alloy 9Cr2Mo) at low loadfrequency The stable carbides and strength matrix maybehelp for the excellent fatigue properties of hardfacing mate-rial When the load frequency is 200Hz fatigue behavior ofthe two alloys does not differ much below 100 cycles but itdiffers dramatically above 10000 cycles which illustrates thatthe strain capacities of the hardfacingmaterial are not as goodas the roll material in higher load frequency The hardfacingmaterial is more sensitive to the change of loading frequencythan the roll material

Figure 7 shows the effect of temperature on fatigue lifeFor 9Cr2Mo fatigue property at 400∘C is not better than thatat 100∘C at the load frequency of 100Hz It manifests temper-ature has a small effect on the fatigue curves of 9Cr2Mowhentemperature is below 400∘CMeanwhile fatigue curves of theoptimum alloy have little change when temperature rangesfrom 100∘C to 400∘C which illustrates that the hardfacingmaterial has good strain capacities during high temperature


9Cr2Mo 100∘C9Cr2Mo 400∘C

10 100∘C10 400∘C

100 1000 10000 100000 1000000 1E710

Number of cycles

01

1

10

Tota

l str

ain

()

Figure 7Δ120576-119873 curves of alloy 9Cr2Mo and the optimumalloy (10)at different temperature in 100Hz load frequency

4 Conclusion

New hardfacing materials with different carbon chromiumand niobium content for cold rolls were designed by orthog-onal experiments methodsThe results show that the interac-tion between the three elements is critical for the hardnessof hardfacing layer Under the condition of certain carboncontent the increase of the CrNb ratio is helpful to increasehardness For the condition of certain chromium contentthe higher carbon content and lower niobium lead to higherhardness When the chemical composition is 05 C 40Cr and 20 Nb the hardness is up to 547 HRC This con-tributed to the fine lath martensite and dispersed distributedcarbidesΔ120576-119873 curves with different load frequency and tempera-

ture for 9Cr2Mo and the new designed alloy were calculatedFatigue behavior of the optimum alloy is as good as that of9Cr2Mo at load frequency of 1Hz and 400∘C

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This research is financially supported by the Nation NaturalScience Foundation (no 51304059) and China ScholarshipCouncil (no 201406705011)

References

[1] G Pantazopoulos and A Vazdirvanidis ldquoFractographic andmetallographic study of spalling failure of steel straightenerrollsrdquo Journal of Failure Analysis and Prevention vol 8 no 6 pp509ndash514 2008

[2] H R B Rad A Monshi M H Idris M R A Kadir and HJafari ldquoPremature failure analysis of forged cold back-up roll ina continuous tandemmillrdquoMaterials and Design vol 32 no 8-9 pp 4376ndash4384 2011

[3] X-F Qin D-L Sun L-Y Xie and Q Wu ldquoHardening mech-anism of Cr5 backup roll material induced by rolling contactfatiguerdquo Materials Science amp Engineering A vol 600 pp 195ndash199 2014

[4] C K Kim S Lee J-Y Jung and S Ahn ldquoEffects of com-plex carbide fraction on high-temperature wear properties ofhardfacing alloys reinforced with complex carbidesrdquo MaterialsScience and Engineering A vol 349 no 1-2 pp 1ndash11 2003

[5] D J Branagan M C Marshall and B E Meacham ldquoHightoughness high hardness iron based PTAW weld materialsrdquoMaterials Science and Engineering A vol 428 no 1-2 pp 116ndash123 2006

[6] B Venkatesh K Sriker andV S V Prabhakar ldquoWear character-istics of hardfacing alloys state-of-the-artrdquo Procedia MaterialsScience vol 10 pp 527ndash532 2015

[7] X H Wang F Han X M Liu S Y Qu and Z D ZouldquoMicrostructure and wear properties of the Fe-Ti-V-Mo-Chardfacing alloyrdquoWear vol 265 no 5-6 pp 583ndash589 2008

[8] E O Correa N G Alcantara L C Valeriano N D BarbedoandR R Chaves ldquoThe effect ofmicrostructure on abrasivewearof a Fe-Cr-C-Nb hardfacing alloy deposited by the open arcwelding processrdquo Surface amp Coatings Technology vol 276 pp479ndash484 2015

[9] A V Khvan B Hallstedt and K Chang ldquoThermodynamicassessment of Cr-Nb-C and Mn-Nb-C systemsrdquo Calphad vol39 pp 54ndash61 2012

[10] Q B Wang Z X Li Y W Shi L Z Wang and F Liu ldquoInteriorcrack and its formation mechanism in overlaying weld of back-up rollsrdquo Engineering Failure Analysis vol 34 pp 268ndash277 2013

[11] C S Bandara S C Siriwardane U I Dissanayake and RDissanayake ldquoFull range S-N curves for fatigue life evaluationof steels using hardness measurementsrdquo International Journal ofFatigue vol 82 part 2 pp 325ndash331 2016

[12] Z L Guo N Saunders P Miodownik and J-P SchilleldquoModelling the strain-life relationship of commercial alloysrdquo inProceedings of the ASME Pressure Vessels and Piping Conferencepp 281ndash287 San Antonio Tex USA July 2007

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Table 1 Chemical composition of hardfacing materials (wt)

C Si Mn Cr Mo W + V + Ti Nb Fe03ndash05 05 15 30ndash50 le20 le21 20ndash60 Bal

2 Experiment and Calculation Method

21 Experimental Procedure Three factors and three-levelorthogonal experiments were adopted to design the hardfac-ing materials The interactions between carbon chromiumand niobium were considered in this study The compositionof hardfacing material is shown in Table 1

The hardfacing materials were deposited on low carbonsteel using the Tungsten Inert Gas Welding Technology Inorder to gain undiluted layer the thickness of hardfacing lay-ers was approximately 8mm

The hardness was tested by Rockwell hardness testingmachine All specimens were etched with a solution of4 nital Microstructure examination of the specimens wascarried out by Olycia M3 optical microscopy (OM) and NovaNano SEM450s scanning electronmicroscopy XPertMPDX-ray diffractometer was used to analyze carbides

22 Fatigue Curves Calculation The 119878-119873 relationship ofmaterials can be obtained using fatigue test [11] However a lotofmoney and timewill be spent So calculating fatigue curveshas great advantages JMatPro a multiplatform software pro-gram for the prediction of the properties of multicomponentalloys was used to analyze the fatigue property (Δ120576-119873 curves)of hardfacing materials

In this method a relationship between monotonic tensileproperties and uniaxial fatigue properties was developed firstand then combined high temperature properties (Youngrsquosmodulus and strength) to evaluate the fatigue curves of thematerial The relationship between the strain range Δ120576 andsubsequent fatigue life 119873 is usually given by the classicalCoffin-Manson Equation

Δ120576

2=Δ120576119890

2+

Δ120576119901

2=Δ120590

2119864+ (Δ120590

21198701015840

)

1119899

1015840

Δ120576

2=Δ120576119890

2+

Δ120576119901

2=

1205901015840

119891

119864(2119873)119887

+ 1205761015840

119891

(2119873)119888

(1)

in which Δ120576 is total strain range in axial fatigue test Δ120576119890is

elastic strain range in axial fatigue test Δ120576119901is plastic strain

range in axial fatigue test 119873 is number of cycles to failure1205901015840

119891

is axial fatigue strength coefficient 1205761015840119891

is axial fatigueductility coefficient 119887 is axial fatigue strength exponent 119888 isaxial fatigue ductility exponent 1198991015840 is cyclic strain hardeningexponent1198701015840 is cyclic strain hardening coefficient

The two equations are usually used to describe the cyclicstress-strain behavior and strain-life relationship [12]

3 Results

31 Hardness Table 2 and Figure 1 give the hardness resultsof orthogonal experiments It can be seen that carbon is

Table 2 Hardness of different samples

C (wt) Cr (wt) Nb (wt) Hardness (HRC)1 03 30 20 4232 03 40 40 683 03 50 60 1454 04 30 40 4005 04 40 60 826 04 50 20 5007 05 30 60 4198 05 40 20 5479 05 50 40 5041198791119895

636 1242 1471198792119895

982 697 9721198793119895

147 1149 6461198721119895

212 414 491198722119895

3273 2323 3241198723119895

49 383 2153119877119895

278 1817 2747

20

25

30

35

40

45

50

Har

dnes

s (H

RC)

Nb2 Nb3Nb1Cr2 Cr3Cr1C2 C3C1Factor

Figure 1 Relationship between hardness and factors

the most effective factor for the hardfacing hardness and theleast is chromium Moreover the hardness is improved withthe increasing of carbon content and the decrease of niobiumcontent However the hardness exhibited a drop and then risewith the increase of chromium content This is related to thecarbon redistribution and carbides content [4] As a strongcarbide forming element niobium carbides will precipitatefirst at high temperature stage The higher the niobiumcontent is the lower the content of carbon in matrix andchromium carbides is and the lower the hardness is Accord-ing to the thermodynamic equilibrium calculation the aver-age mass fraction of NbC is 388 331 and 345 in thelevel of 30 Cr 40 Cr and 50 Cr respectively As NbChas significant effect on hardness the hardness exhibited adrop and then rise with the increasing chromium contentThrough the analysis of Figure 1 05 C 30 Cr and 20


2 3 4 5 6 71 98


0

1

2

3

4

5

6

Mas

s fra

ctio

n of

carb

ides

(wt

)


20120583m

(a)

20120583m

(b)










20120583m

NbC

(a)

20120583m

NbC

(b)


(Ti Nb)C

8020 40 60

2120579 (deg)

0

2000

4000

6000

8000

10000

12000

Inte

nsity

(cps

)

120572-Fe

(a)

M7C3(Ti Nb)C

8020 40 60

2120579 (deg)

1000

1500

2000

2500

3000

3500

4000

Inte

nsity

(cps

)

120572-Fe

(b)


1

10

Tota

l str

ain

()

100 1000 10000 100000 1000000 1E710

Number of cycles


10 1Hz10 200Hz






10 100∘C10 400∘C

100 1000 10000 100000 1000000 1E710

Number of cycles

01

1

10

Tota

l str

ain

()


4 Conclusion





Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










2 3 4 5 6 71 98


0

1

2

3

4

5

6

Mas

s fra

ctio

n of

carb

ides

(wt

)


20120583m

(a)

20120583m

(b)










20120583m

NbC

(a)

20120583m

NbC

(b)


(Ti Nb)C

8020 40 60

2120579 (deg)

0

2000

4000

6000

8000

10000

12000

Inte

nsity

(cps

)

120572-Fe

(a)

M7C3(Ti Nb)C

8020 40 60

2120579 (deg)

1000

1500

2000

2500

3000

3500

4000

Inte

nsity

(cps

)

120572-Fe

(b)


1

10

Tota

l str

ain

()

100 1000 10000 100000 1000000 1E710

Number of cycles


10 1Hz10 200Hz






10 100∘C10 400∘C

100 1000 10000 100000 1000000 1E710

Number of cycles

01

1

10

Tota

l str

ain

()


4 Conclusion





Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










20120583m

NbC

(a)

20120583m

NbC

(b)


(Ti Nb)C

8020 40 60

2120579 (deg)

0

2000

4000

6000

8000

10000

12000

Inte

nsity

(cps

)

120572-Fe

(a)

M7C3(Ti Nb)C

8020 40 60

2120579 (deg)

1000

1500

2000

2500

3000

3500

4000

Inte

nsity

(cps

)

120572-Fe

(b)


1

10

Tota

l str

ain

()

100 1000 10000 100000 1000000 1E710

Number of cycles


10 1Hz10 200Hz






10 100∘C10 400∘C

100 1000 10000 100000 1000000 1E710

Number of cycles

01

1

10

Tota

l str

ain

()


4 Conclusion





Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











10 100∘C10 400∘C

100 1000 10000 100000 1000000 1E710

Number of cycles

01

1

10

Tota

l str

ain

()


4 Conclusion





Acknowledgments


References















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article composition design and fatigue...

Documents