1. Fabrication and Characterization of novel
W80Ni10Nb10 alloy produced by mechanical
alloying
Presented by
Rishabh Saxena
NATIONAL CONFERENCE ON PROCESSING & CHARACTERIZATION OF MATERIALS (NCPCM 2015)
(12th December, 2015)
Contributing authors : R. Saxena, A. Patra, S. K. Karak, A. Pattanaik, S. C. Mishra
Department of Metallurgical and Materials Engineering
NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA
ROURKELA-769008
2. Brief outline
Aims and Objective
Introduction and Background
Materials & Methods
Result & Discussion
Conclusions
Future scope of work
References
2
3. Aims and objective
To fabricate W based alloys made by mechanical alloying, for kinetic energy
penetrator in defense application, structural applications in fusion reactors
designed for operation at higher (>550oC) operating temperature.
To characterize W80Ni10Nb10 alloy produced through mechanical alloying.
3
6. Introduction & Background
Why tungsten?
• High melting point (34200C)
• High hardness (9.8 GPa), Modulus of Elasticity=407 GPa.
Good thermal conductivity (1.74 W/cm K) , low
co-efficient of thermal expansion.
• Low-activating metal in radiation environment with low
sputtering yield.
(W.F. Smith, McGraw-Hill, 1993)
6
7. Introduction & Background
Problems?
• High ductile brittle transition temperature.
• Poor Oxidation resistance at elevated temperature.
[Anshuman Patra, Microscopy and Anlysis , 26 (5), (2012)]
Why Nickel Addition ?
• Improves ductility.
• Promotes liquid phase sintering which can improve mechanical
(hardness) and Physical property (density).
[Kemp et al., Jou. Of Less Common Metal, 175 (1991)]
7
8. Introduction & Background
Niobium Addition?
• High melting point (2468°C).
• To provide enhanced oxidation resistance at elevated temperature
[ A. Patra, Microscopy and Analysis, (2012)]
Why nanostructuring ?
• To lower sintering temperature. [R. malewar et al., J. Mater. Res., 22 (2007)]
• To improve the mechanical properties. [H. Glieter, Acta. Mater., 48 (2000)]
8
9. Introduction & Background (Basis of Nickel Selection)
G. D. Samolyuk et al. Fusion Reactor Materials Program (2011)
Reduced peierls
barrier (barrier to
overcome for
dislocation
movement) & low
cost as compared to
other rare earth
metals.
9
10. Materials and Method
Elemental W-Ni-Nb
Mechanical Alloying (20 h)
Compaction (500 MPa)
Sintering (1500°C, 2 h
holding)
XRD at various milling times, SEM,
TEM.
Density/Porosity
XRD,SEM
Hardness WearDensity
10
11. Materials and Method
FRISTSCH planetary ball mill
Room temperature milling
Chrome steel vials and 10 mm balls
300 rpm, 10:1 (ball to powder weight)
Wet milling with toluene
Elemental powders of W, Ni, Nb (purity 99.5%, Sigma
Aldrich) with initial particle of 100-150 µm (for W, Ni,
Nb)
Material
Designation
W
(wt %)
Ni
(wt %)
Nb
(wt%)
M1 80 10 10
Composition (initial) of the powder blends for mechanical alloying /milling
11
14. Materials and Method
Equipment and Method Parameters measured
XRD (X-Pert High Score, Origin,
Powdll software)
1. Crystallite size, Lattice strain, Lattice parameter, Dislocation
density, phase evolution of milled powder
2. phase evolution in sintered product.
SEM Morphology and compositional study of milled powder.
TEM & SAD pattern Crystallite size determination and Crystal structure Indentification.
Archimedes’s principle Density/porosity measurement.
Microhardness Tester Hardness evaluation (50,100,500,1000 gram-force load, 10 sec dwell
time)
Ball on plate wear tester Wear study (load = 20 N,30N, time = 10 mins, speed= 25 r.p.m
14
15. Materials and Method
Crystallite size & Lattice strain calculation:
𝛃 𝒄𝒐𝒔 𝛉 =
𝟎.𝟗𝟒𝝀
𝑫
+ 𝛆sin 𝛉 (1)
β is the full width half maxima (FWHM), D is the crystallite size and 𝛆 is the lattice strain.
[R. Jenkins et al. Introduction to X-ray Powder Diffractometry (1996)]
Dislocation density calculation:
𝝆 𝐝 = 𝟐√𝟑
𝜺 𝟐
𝑫 𝐗 𝒃
𝟏
𝟐
(2)
b : burgers vector of dislocations, b = (a√3)/2 for the bcc structure, a= cell parameter= lattice
parameter, D = crystallite size, ε = lattice strain. (Zhao et al. Acta Mater, 2001)
15
16. Materials and Method
Sintered Density Calculation:
𝛒 𝐬=
𝑾 𝐚
𝑾 𝐬𝐚𝐭−𝑾 𝐬𝐮𝐬𝐩
𝑿 𝝆 𝒘
𝐠𝐦
𝐜𝐦 𝟑 (3)
𝑊a: weight of the sintered sample in air. 𝑊sat : weight of the sample with all the open
porosity saturated with water, 𝑊susp : weight suspended in water. 𝜌 𝑤 : density of water.
[Ozkan et al. J. Eur. Ceram. Soc , 1994]
Hardness Measurement: 𝐇𝐕 = 𝟏. 𝟖𝟓𝟒𝟒
𝑷
𝒅 𝟐 (4) GPa conversion= 0.009807 X HV
P : applied load, d : diagonal length of the indentation. [ L. Ayers, The Hardening of Type
316 L Stainless Steel Welds with Thermal Aging, 2012]
Sliding distance : 𝐒𝐥𝐢𝐝𝐢𝐧𝐠 𝐃𝐢𝐬𝐭𝐚𝐧𝐜𝐞 𝐒. 𝑫 =
𝑹
𝟔𝟎
× 𝐭 × 𝟐𝝅𝒓 (𝟓)
R : number of rotation per minute traversed by the indenter on sample surface, t: time in sec (600 s),
r : track radius (4 mm) measured from the center of the sample to the track. [ A. Patra, Microscopy
and Analysis (2015)] 16
17. Results and Discussions
XRD Study of Milled Powder
Fig. 1. XRD pattern of W80Ni10Nb10 alloy milled for 20 h.
17
18. Results and Discussions
XRD Study of Milled Powder
Fig. 2. Variation of crystallite size and lattice strain of W with milling time in W80Ni10Nb10.
18
19. Results and Discussions
XRD Study of Milled Powder
Fig. 3. Variation of a) Dislocation density and b) Lattice parameter of W in W80Ni10Nb10
with milling time. 19
20. Results and Discussions
SEM Study of Milled Powder
Fig. 4. SEM images of powder morphology of W80Ni10Nb10 alloy after different milling times: (a) 0 h,
(b) 5 h, (c) 10 h, and (d) 20 h. 20
21. Results and Discussions
TEM Study of Milled Powder
Fig. 5. TEM image of W80Ni10Nb10 powder milled at 20 h: (a) Bright field TEM image and
(b) corresponding SAD pattern. 21
22. Results and Discussions
XRD Study of Sintered alloy
Fig. 6. XRD pattern of W80Ni10Nb10 alloy milled for 20 h and sintered at 1500°C for 2 h.
22
23. Results and Discussions
SEM Study of Sintered alloy
Fig. 7. SEM micrograph of 20 h milled W80Ni10Nb10 alloy sintered at 1500°C for 2 h.
Calculated sinterability
𝑺𝒊𝒏𝒕𝒆𝒓𝒆𝒅 𝒅𝒆𝒏𝒔𝒊𝒕𝒚
𝒕𝒉𝒆𝒐𝒓𝒊𝒕𝒊𝒄𝒂𝒍 𝒅𝒆𝒏𝒔𝒊𝒕𝒚
= 𝟗𝟎. 𝟖%
23
24. Results and Discussions
Fig. 8. Variation of Hardness of W80Ni10Nb10 alloy milled for 20 h and sintered
at 1500°C for 2 h. 24
Hardness Study
25. Results and Discussions
Fig. 9. Variation of wear depth of W80Ni10Nb10 alloy milled for 20 h and sintered at
1500°C for 2h.
Applied Load (N) Wear rate (× 10-15) m3/Nm
20 N 4.01
30 N 4.43
J. Archard, J. Appl. Phys, 1953
25
Wear Study
27. Conclusions
W80Ni10Nb10 alloy powder can be effectively produced by mechanical alloying.
Crystallite size of tungsten in W80Ni10Nb10 reduces with increasing milling time and
minimum crystallite size of 34 nm is achieved at 20 h of milling.
Expansion of the lattice parameter of tungsten in W80Ni10Nb10 records 0.04% at 10 h and
contraction upto 0.02% at 20 h of milling.
Bright field TEM image and corresponding SAD pattern reveals the presence of
nanocrystalline BCC-W phase with 20-30 nm in size at 20 h of milling.
Presence of NbNi intermetallic is evident in the sintered alloy due to Ni rich liquid phase
formation at the selected sintering temperature.
Microhardness value increases with decrease in load due to smaller indentation and
detection error of the diagonals of the indentation at lower loads.
Wear rate at maximum wear depth increases with increase in load due to enhanced abrasion
effect at higher load.
27
28. Future scope of study
Fabrication of alloy through advanced consolidation techniques (such as
spark plasma sintering)
Improvement of high temperature strength through Oxide dispersion.
Investigate the effect of increasing oxide content on mechanical properties of
W based alloy.
Study the effect of increasing Nb content with respect to high temperature
response (oxidation behavior)
28
29. References
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[2] Glieter H 2001 Acta. Mater 48 1.
[3] Koch C 1997 Nanostruct. Mater 9 13.
[4] Suryanarayana C 1998 Mechanical Alloying ASM Handbook 7 80.
[5] Suryanarayana C 2001 Prog. Mater. Sci 46 1-184.
[6] Cullity B 1978 Elements of X-ray diffraction 2 (Addison Wesley: Philippines) 86-88.
[7] Williamson G and Hall W H 1953 Acta. Mater 1 22.
[8] Zhao Y H, Sheng H W and Lu K 2001 Acta. Mater 49 365–375.
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3754.
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Inc: New York).
[11] Chattopadhayay P, Nambissan P M G, Pabi S K and I Manna 2001 Appl. Surf. Sci 182 308-
312.
[12] Singh V 2002 Physical Metallurgy 1 (Standard Publisher Distributor: New Delhi) 63-64.
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Materials (Rourkela) 75 (Bristol: UK/IOP Science) 012032. 29
30. References
[14] Li X, Cheng Z, Hu K, Chen H and Yang C 2015 Vacuum 114 93-100.
[15] Ozkan N and Briscoe B J 1994 J. Eur. Ceram. Soc 14 143-151.
[16] Ayers L J 2012 The Hardening of Type 316 L Stainless Steel Welds with Thermal Aging
Massachusetts Institute of Technology.
[17] Dieter G 1928 Mechanical Metallurgy SI Metric Edition (McGraw-Hill Co: Singapore)
189-93.
[18] Patra A, Karak S K and Pal S 2015 Microscopy and Analysis 29(4) 18-22.
[19] Nuthalapati M, Karak S K and Basu A 2015 Materials Today: Proceedings 2 1109- 1117.
[20] Archard J F 1953 J. Appl. Phys 24 (8) 981-988.
[21] Smith W. F, 1993 Structure and Properties of Engineering Alloys, Second Edition,
McGraw- Hill, USA,
[22] Samolyuk G. D, Osetskiy Y. N, and Stoller R. E., 2011 Fusion Reactor Materials Program,
DOE/ER-0313/50, 50 124-128.
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