alloying of metal and carbides on an aluminium alloy surface by electron beam welding

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This article was downloaded by: [University of Colorado at Boulder Libraries] On: 21 December 2014, At: 20:38 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Welding International Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/twld20 Alloying of metal and carbides on an aluminium alloy surface by electron beam welding H Yamanaka a & S Shimizu a a NDK Processing Centre KK , Published online: 05 Jan 2010. To cite this article: H Yamanaka & S Shimizu (1998) Alloying of metal and carbides on an aluminium alloy surface by electron beam welding, Welding International, 12:2, 160-164, DOI: 10.1080/09507119809448469 To link to this article: http://dx.doi.org/10.1080/09507119809448469 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms- and-conditions

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Page 1: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

This article was downloaded by: [University of Colorado at Boulder Libraries]On: 21 December 2014, At: 20:38Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41Mortimer Street, London W1T 3JH, UK

Welding InternationalPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/twld20

Alloying of metal and carbides on an aluminium alloysurface by electron beam weldingH Yamanaka a & S Shimizu aa NDK Processing Centre KK ,Published online: 05 Jan 2010.

To cite this article: H Yamanaka & S Shimizu (1998) Alloying of metal and carbides on an aluminium alloy surface by electron beamwelding, Welding International, 12:2, 160-164, DOI: 10.1080/09507119809448469

To link to this article: http://dx.doi.org/10.1080/09507119809448469

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in thepublications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations orwarranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsedby Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings,demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectlyin connection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Page 2: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

lVelding Internntiorrnl 1998 I 2 ( 2 ) 160-164 Selectedfroni lvelding Technique 1997 45 ( 4 ) 108-1 12; Reference lVT/97/4/108: Translntion 2218

Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

H Y A M A N A K A a n d S S H l M l Z U N D K Processing Centre K K

Introduction

Arc, plasma, laser and electron beam welding processes are used for alloy surfacing purposes to improve the wear resistance of aluminium alloy surfaces. Arc, plasma and laser welding processes, however, readily generate defects, such as porosity, in the hard surfacing layer.

Electron beam welding is used for alloying at a high energy density in a high vacuum and produces a good- quality hard surfacing layer containing very few defects, such as porosity. The technique is now seeing practical applications in the formation of hard surfacing layers using Ni or Si alloys. The hard surfacing layers produced by metals being used on alloys, however, generally perform well in relation to abrasive wear, but perform less well in relation to adhesive wear. To improve the adhesive wear resistance, it is necessary to disperse carbides in the hard surfacing layer. It is generally found that, when carbide powders are added to the molten pool by electron beam welding in a high vacuum, the powder disperses, and it is difficult to obtain a good-quality hard surfacing layer.

This paper describes the use of metal and carbide composite alloys, the alloying of metals and carbides on aluminium alloy surfaces, the method of forming hard surfacing layers with superior wear resistance, and the properties of the hard surfacing layers produced.

Alloys

The alloys used were those involving carbide powders being packed in a metal tube and drawn into wire. By this method, some ingenuity is thus applied particularly to the alloy material.

Properties

Metal coating of carbide powders

Figure 1 shows that, when just a carbide powder is used as the alloy, it is dispersed by the force of repulsion due to the electric charge between the particles. If the carbide is coated with metal, however, dispersion of the metal is much reduced, and it accumulates in the molten Al.

Table 1 shows the amount of wetting between carbides and molten metals. The amount of wetting between car- bides and molten A! is very small, so that it is difficult to add carbides to molten Al. If the carbide concerned is coated with high-wetting metal, however, the metal fused by the electron beam satisfactorily covers the carbide sur- face, so that the carbide can be easily added to molten A!.

Electron beam Electron beam a 000

a 000

Carbide particles Metal-plated carbide particles

1) Large electrical resistance of 1) Small electrical resistance on particle

2) Increase in electric charse of 2) Decrease in electric charoe of

panicles themselves; large contact resistance between particles between particles

surface: small contact resistance

panicles panicles

to electric charge between particles 3) Dispersion by force of repulsion due 3) Decrease in dispersion of particles

1 Dispersion of carbide particles by electron beam.

Table I Amount of wetting between carbides and molten metals in vacuum

Amount of wetting between carbides Carbides Metals and molten metals (mN/m)

Tic AL -786 Ni 1,547 c u 25.7

Ni 1,689 c u 668

wc co 1,873

NbC AL - 649

Packing of carbide powders in metal pipe under vacuum

To deposit the carbide powder on the alloying A1 alloy surface and to prevent the powder from being dispersed by the force of repulsion due to vaporisation of the weld metal during welding, the coated powder is packed in a metal tube and thus used as the alloy material. If air is present in the metal tube, the tube shape becomes non-uniform during wire-drawing, and, when alloying is performed by electron beam welding, welding operability is impaired, and defects readily occur in the hard surfacing layer. For this reason, it is necessary to pack the alloying carbide powder in the metal tube under a vacuum.

Production method

The metal-coated carbide powders used were TiC- 30vol%Ni, NbC-30vol%Ni, and NbC-30vol%Cu pow- ders produced by electroless plating of Ni or Cu on NbC and TIC powders as well as 17%Co-WC poivder pro- duced as a granular composite for hot spraying using WC and Co powders. The particle sizes of the carbide powders all ranged between 10-40 pm.

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Page 3: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

Alloying of metal arid carbides 011 A1 sirrfnce 161

These carbide powders were packed in an A1 or Cu tube, both ends were plugged by electron beam welding, and the inside of the tube was evacuated. This tube was then drawn into wire by stretching and used as 3 mm dia. and 4 mm dia. alloy materials.

Table 2 shows the constitutions of the alloy materials and their cross-sections.

Alloying by electron beam welding

Figure 2 shows how the alloy material was embedded in a groove cut in the A1 alloy base material surface and alloyed by electron beam welding. Table 3 lists the electron beam welding conditions. Electron beam weav- ing was performed to extend the bead width, to homogen- ise the hard surfacing layer components, and to control and homogenise the penetration depth.

Tcible 3 Constitutions of alloy materials and their cross-sections

Tube Dimensions (mm) Packed powder

A f 3 0.d. Plating of 30vol%Ni or A f 4 0.d. 3Ovol%Cu on Tic and

c u 3 0.d. l 7 % c o - w c NbC powders

I t .,

3 0.d. Al tube

a 3 0.d. C u tube

4 0.d. Al tube

Table 3 Electron beam welding conditions

Acceleration voltage, kV Beam current, mA Weaving Waveform Weaving Frequency, Hz Weaving Width, mm Welding speed, mm/min Processing distance, mm Dcgree of vacuum, Torr

40 45-65 Triangular 500

8 300 320 4 x 1 0 - ~

Alloy material

Al alloy base material

2 Groove cut in A/ alloy surface.

Alloy materials Bead appearance of hard surfacing layers

Al .D. x 2 1.D

130:

-3Ovol%Ni

-30vol%cL

1 7 %co-\vc

Base material: A5052

3 Bead appearance of hard surfacing layers.

Properties of hard surfacing layer

Bead appearance of hard surfacing layer

Figure 3 shows the bead appearance of the hard surfacing layer produced with each alloy material. All the alloy materials tested give good bead appearance except for the case where Cu-plated TIC was used. In Cu-plated TIC, T i c and Cu have poor wetting, which results in a poor bead appearance.

Cross-sectional microstructure of hard surfacing layers

Figure 4 shows the cross-sectional microstructure of the hard surfacing layers. The hard surfacing layers produced with all the alloy materials tested contain no defects, and the carbides are uniformly dispersed in them.

Thickness of hard surfacing layer

Figures 5 and 6 show the relationship between the beam current and hard surfacing layer thickness of the hard surfacing layers produced with the alloy materials tested. Table 4 lists the types and compositions of alloys produced when Ni or Cu-plated carbides were packed in an A1 tube.

Table 4 Types and compositions of alloys

A1 tube Compositions, Alloys Powders dimensions, mm VOMO

At-Tic-Ni TiC-30vol%Ni plating

AC-TIC-Cu TiC-3Ovol%Cu plating

AC-NbC-Ni NbC-30vol%Ni plating

AC-NbC-Cu NbC-30vol%Cu plating

3 0.d. x 2 i.d. 4 o.d x 3 id .

3 0.d. x 2 i.d.

4 0.d. x 3 i.d. 3 0.d. x 2 i.d.

4 0.d. x 3 i.d.

3 0.d. x 2 i.d. 4 0.d. x 3 i.d.

AL: 57 TIC: 30 Ni: 13 A(: 51 T i c 30 cu: 13 Af: 51 N b C 30 Ni: 13 AL: 57 N b C 30 cu: 13

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Page 4: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

162 Ynmniinka mid Shiinizu

TiC-30vol%Ni plating powder NbC-30vol%Ni plating powder

Base material: A5052

4 Microstructure of hard surfacing layers.

-II

f 3 - I-

2 -

1 -

0 1 , I I I I I 40 45 SO S5 60 65 70

Beam currenl, mA

5 Relationship between beam current and thickness of hard surfacing layer (1).

0 1 I I I I

i. mm

6 Relationship between beam current and thickness of hard surfacing layer 12).

Cu (3.1°-D. X 2.0'.'.)

17%Co-WC powder

I 5 mrn I

The thickness of the hard surfacing layer corresponds to the penetration depth and increases with an increasing beam current. For the hard surfacing layers produced with Ni or Cu-plated carbides, the thickness of the hard surfacing layer produced with an AI-Ni matrix is greater than that produced with an Al-Cu matrix.

Areal fractions of carbides in hard surfacing layers

Figures 7 and 8 show the relationship between the beam current and areal fractions of the hard surfacing layers produced with the alloy materials tested. The areal fraction of each hard surfacing layer increases with a decreasing beam current or an increasing alloy carbide content. The limiting value of the carbide areal fractions of the hard surfacing layers produced with Ni or Cu- plated NbC and Tic alloys, however, is around 20%, being around 30% for the Cu + I7%Co-WC alloy. Under welding conditions involving this limiting value being exceeded, heavy dispersion of the carbide powder occurs, and a sound bead is never formed.

01 I I I I I

40 45 50 55 60 65 Beam current, mA

7 Relationship between beam current and carbide areal fraction of hard surfacing layer (1).

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Page 5: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

Alloying of iiietnl mid carbides 011 A1 sirrfnce 163

Beam current, m A

s, m m

8 Relationship between beam current and carbide areal fraction of hard surfacing layer (21.

Figure 9 shows the dispersion conditions of the car- bides in the hard surfacing layers at a carbide areal fraction of around 17%.

Hardness, cracking, and Ni and Co contents of hard surfacing layers

Figures 10 and 1 1 show the relationship between the hardness, cracking and Ni or Cu contents of the hard surfacing layers produced with the alloy materials tested. The hardness here refers to the matrix hardness. For all hard surfacing layers, the hardness increases with an increasing Ni or Cu content. If the hard surfacing layer of the Ni or Cu-plated NbC and Tic alloys reaches HV244 and if that of the hard surfacing layer of the Cu + 17%Co- WC alloy reaches HV244, cracking occurs.

The hardness of the hard surfacing layer of the Cu + 17%Co-WC alloy is greater than that of the hard

Alloy material: AI-Tic-Ni; carbide areal fraction: 16.1%

Alloy material: AI-NbC-Ni: carbide areal fraction: 17.7%

0 I AI-TIC-Ni

0 I Al-NbC-Cu

Base material: A5052 0 Y

Occurrence of cracking I

AI-Ni hard surfacing layer

>

so l 1 I 1 1 I 8 I I 1 I I I I I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Ni or Cu content (wt%)

10 Hardness, cracking, and Ni or Cu content of hard surfacing layer.

x

U 0

0 - x - L 0 U 1 v1 M

c

- E

t?

5

F

Y "

11

l o o t

Cu content, wt%

Hardness, cracking, and Cu content of Cu+77%Co-WC hard surfacing layer.

surfacing layer of Cu alloy, whereas the hardness of the hard surfacing layers of the Ni or Cu-plated NbC and TIC alloys is equivalent to that of the hard surfacing layers of Ni or Cu alloys. This is due to the fact that the WC and Co of the Cu+ 17%Co-WC alloy melts and solidifies in the matrix but that, in Ni or Cu-plated NbC and TIC alloys, NbC and TIC scarcely melt at all in the matrix.

With regard to the Ni or Cu content of the hard surfacing layers of the Ni or Cu-plated NbC and Tic alloys, Figure 12 shows the relationship between the calculated values of the Ni or Cu content of the alloys and the measured values determined by EPMA of the hard surfacing layers. The Cu content shows good agreement between the calculated and measured values, and the measured values of the Ni content are also around 0.9-fold of the calculated ones. The yields of Ni or Cu in the hard surfacing layers are good.

Alloy material: AI-NbC-Cu; carbide areal fraction: 17.2%

Alloy material: Cu + 25 vol% l17%CoWC); carbrde areal fraction: 16%

1 mm U

9 Dispersion conditions of carbides in hard surfacing layers.

Wear resistance of hard surfacing layers

Figure 13 presents the results obtained during Ogoshi type high-speed wear tests of the hard surfacing layers

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Page 6: Alloying of metal and carbides on an aluminium alloy surface by electron beam welding

164 Ynntn11nkn alln sllilnizu

._ c - 01 Calculated Ni or Cu content wt% n - v)

12 Calculated and measured values of Ni or Cu content of hard surfacing layer.

0.5

26 xio-5 500

24 - Symbol Alloy materials

5 1 6 -

1 4 -

: Rotating disc: SUJZ

Final load 20.6 N Friction distance: 600 m m

i

' z i . .' 3 -

I I I I I

For the hard surfacing layers of the Ni or Cu-plated NbC and T i c alloys and Cu + 17%Co-WC alloy, some 2-3-fold the wear resistance of the A5052A1 base material is invariably found at a high wear rate. As the wear rate decreases, however, the hard surfacing layers of the NbC and Tic alloys show a reduced wear resistance equivalent to that of the base material, whereas the hard surfacing layer of the Cu + 17%Co-WC alloy shows an improved wear resistance reaching around 10-fold that of the base material at a wear rate of 0.083 m/sec.

The wear resistance of the hard surfacing layer of Cu alloy is equivalent to that of the hard surfacing layers of the Ni or Cu-plated carbides.

Conclusions

Electron beam welding can now be used to form a high-quality hard surfacing layer on aluminium alloy

13 Results obtained during Ogoshitype high-speed wear tests of hard surfacing layers produced with alloy materials tested.

surfaces. To improve the wear resistance, however, i t is necessary to add ceramic or metal elements to the hard surfacing layer. As described in this paper, alloy powders can be added to the hard surfacing layer produced by electron beam welding. If alloy powders with these ceramic or metal elements are used by the proposed method, the composition of the hard surfacing layer can be easily adjusted to obtain a hard surfacing layer offering superior wear resistance.

References

1 Yarnanaka and Shirnizu: Proc nat confJpn Weld SOC, 1995.56, (4), 240-24 1.

2 Yarnanaka and Shirnizu: Proc 91st autumn conf Jpn lnst Light hlet, 1996, 291-292.

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