The document discusses characterization of three high nickel content alloys - Maraging Grade 300, INCONEL 600, and INCONEL 718 - before and after undergoing an arc activated plasma nitriding process. The objectives were to increase surface hardness and wear resistance at room and high temperatures. Samples underwent nitriding and were analyzed for their mechanical, structural, and tribological properties using nanoindentation, XRD, SEM, and wear testing. Results showed the nitrided samples exhibited increased surface hardness, nitrogen diffusion depths up to 18 microns, and formation of nitride phases. Wear resistance significantly improved for the nitrided INCONEL alloys but not for nitrided Maraging Grade 300.

1. Mechanical, Structural and Tribological
Characterisation of High Nickel Content Alloys
before and after Arc Activated Plasma Nitriding
aintech@ain.es
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding

2. Mechanical,
Structural
and
Tribological
Characterisation of High Nickel Content Alloys
before and after Arc Activated Plasma Nitriding
J. Fernández, E. Almandoz, J. Arrikaberri, S. Kulkarni, J. F. Palacio,
G.G. Fuentes, J.A. García, R. Rodríguez
AIN – Asociación de la Industria Navarra, Spain
IVC-19 / ICN+T 2013 and partner conferences
9th – 13th September 2013, Paris (France)

3. Outline
1. Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 3

4. Outline
1.Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 4

5. The alloys under study
1) Maraging Grade 300, which belongs to the group of maraging steels with
18% Ni and Co containing.
C (%)
Ni (%)
Co (%)
Mo (%)
Ti (%)
Al (%)
Fe (%)
Specified
< 0.03
17-19
8.5-9.5
4.7-5.2
0.6-0.7
< 0.15
Balance
Measured
0.008
17.31
9.05
5.10
0.66
0.11
Balance
Chemical composition of Maraging Grade 300
Samples
30.3 ± 0.2 HRc after quenching at 820 ºC during 1 h
52.1 ± 0.2 HRc after aging at 485 ºC during 3h
Dimensions: Ø = 35 mm; thickness = 5 mm
Grinded and polished to Ra ~ 10 nm
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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6. The alloys under study
2) INCONEL alloy 600, which belongs to the group of nickel superalloys.
C (%)
Cr (%)
Fe (%)
Mn (%)
Si (%)
Cu (%)
S (%)
Ni (%)
Specified
< 0.15
14-17
6-10
≤1
≤ 0.50
≤ 0.50
≤ 0.015
Balance
Measured
0.12
16.3
9.1
0.54
0.43
0.32
0.011
Balance
Chemical composition of INCONEL alloy 600
Samples
17.0 ± 0.2 HRc
Dimensions: Ø = 40 mm; thickness = 5 mm
Grinded and polished to Ra ~ 10 nm
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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7. The alloys under study
3) INCONEL alloy 718, which belongs to the group of nickel superalloys.
C (%)
Cr (%)
Fe (%)
Mo (%)
Ti (%)
Al (%)
Si (%)
B (%)
Specified
≤ 0.0080
17-21
17
2.8-3.3
0.65-1.15
0.20-0.80
≤ 0.35
≤0.0060
Measured
0.006
17.6
17.1
2.9
0.96
0.55
0.30
0.002
Co (%)
Cu (%)
Mn (%)
Nb (%)
P (%)
S (%)
Ni (%)
Specified
≤ 1.0
≤ 0.30
≤ 0.35
4.75-5.5
≤ 0.015
≤ 0.015
Balance
Measured
0.75
0.22
0.26
5.1
0.009
0.012
Balance
Chemical composition of INCONEL alloy 718
Samples
41.8 ± 0.8 HRc
Dimensions: Ø = 40 mm; thickness = 4 mm
Grinded and polished to Ra ~ 10 nm
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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8. Outline
1. Introduction
2.Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 8

9. Objectives
Study the mechanical, structural and tribological
properties of high nickel content alloys before and
after an arc activated plasma nitriding process.
What for?
Increasing the superficial hardness
Increasing the wear resistance (room &
high temperature)
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 9

10. Outline
1. Introduction
2. Objectives
3.Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 10

11. Arc activated plasma nitriding
Spanish patent: ES 2 344 981 B1 in 2011
and European patent EP 2 369 028 B1 in
2013.
1: Reactor
2: Samples
3: Electric arc discharge units
4: Heat source
5: Sample holder
6: Electron collector (anode)
- 6.1: Electric field concentrator
spirals
7: Gas inlet
8: Vacuum system
9: Pulsed DC current source
10: DC current source
11: DC power system
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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12. Arc activated plasma nitriding
Steps
eIonized
gas
- N + Ar (+H )
e 2
2
+
+
e-
+
Vacuum: 5x10-3 Pa
Pre-heating: 350 ºC
Cleaning: Ar
Nitriding: 1 Pa, 425 ºC, 60 min
90 sccm N2 & Ar
Cooling down
PVD scheme
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 12

13. Arc activated plasma nitriding
Characteristics
High ionization rate
Low pressure
Benefits
High ratio of active specimens
Versatility for future treatments
(DUPLEX treatments: nitriding + PVD,
nitriding + oxidation)
No formation of white layer
Labelling
Material
Nitrided
Maraging 300
MAR-3
MAR-3N
INCONEL 600
METAPLAS PVD MZR 323 equipment
Untreated
INC-6
INC-6N
INCONEL 718
INC-7
INC-7N
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 13

14. Outline
1. Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 14

15. Chemical analysis: GD-OES
70
MAR-3N
C
Fe
Mo
N
O
Ti
Co
Ni
60
Atomic %
50
40
30
20
10
INC-6N
INC-7N
0
3
70
C
Cr
Fe
N
O
Si
Ni
Cu
Mn
60
50
Atomic %
6
40
30
20
9
12
Depth (microns)
15
70
18
Al
C
Cr
Fe
Mo
N
O
Ti
Co
Ni
60
50
Atomic %
0
40
30
20
10
10
0
0
0
1
2
3
Depth (microns)
4
5
0
1
2
3
4
5
Depth (microns)
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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16. Chemical analysis: GD-OES
Nitrogen profiles
MAR-3N
12
18
INC-6N
INC-7N
16
14
N (atomic %)
N (atomic %)
10
8
6
4
12
10
8
6
4
2
2
0
0
2
4
6
8
10
12
Depth(microns)
14
16
18
20
0
0,0
0,5
1,0
1,5
2,0
2,5
Depth (microns)
• MAR-3N shows longer profiles with less nitrogen concentration than INCONEL
alloys, and a longer diffusion zone.
• Both INCONEL alloys show very similar nitrogen profile, with a plateau of ~ 14-15%
of nitrogen content, that decreases drastically .
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 16
3,0

17. Microscopy: SEM of the fracture
MAR-3
INC-6
INC-7
MAR-3N
INC-6N
INC-7N
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 17

18. Mechanical properties (Nanoindentation)
Test parameters
• 10 x10 indents, 25 µm space between
indents
• Decreasing Loads from 10 mN to 100 µN
(in 100µN steps)
• Loading rate constant
• Berkovich Tip radius (150 nm)
• E and H
Oliver and Pharr Method
HYSITRON nanoindenter TI950
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 18

19. Mechanical properties (Nanoindentation)
REFERENCES (Non nitrided samples): MAR-3, INC-6 & INC-7
Er values between 150
GPa and 200 GPa for all
the samples.
MAR-3
INC-6
INC-7
H values of ~ 10 GPa for
MAR-3 and INC-7 and of
~ 7 GPa for INC-6.
Sample
MAR-3
52.1 ± 0.2
INC-6
17.0 ± 0.2
INC-7
MAR-3
INC-6
INC-7
HRc
41.8 ± 0.8
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 19

20. Mechanical properties (Nanoindentation)
MAR-3 & MAR-3N
MAR-3N
MAR-3
Slightly
lower
Er
compared to the as
received MAR-3.
Increase of hardness by
40%, especially at
higher loads.
MAR-3N
MAR-3
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 20

21. Mechanical properties (Nanoindentation)
INC-6 & INC-6N
Similar Red. Modulus.
INC-6N
INC-6
Dramatic increase of
superficial
hardness
(more than x2) with
respect to the as
received INC-6.
INC-6N
INC-6
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 21

22. Mechanical properties (Nanoindentation)
INC-7 & INC-7N
Similar Red. Modulus
INC-7N
INC-7
Dramatic increase of
hardness (x2) with
respect to the as
received
INC-7,
especially at higher
loads.
INC-7N
INC-7
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 22

23. XRD analysis
MAR-3 & MAR-3N
Cr Kα (λ = 2.29110 Å)
BB, 40 KV, 30 mA
Room T, 0.02º step, 0.5 s/step
There is no austenitic
phase 43.64º, 50.76º &
74.58º for γ(111), γ(200) &
γ(220).
Fe3N
Fe4N
Fe-α (101)
a.u.
Peaks of Fe4N, FeNi3N,
Fe3N and
Fe3NiN are
observed.*
MAR-3
MAR-3N
40
50
60
70
Fe3N
XRD test conditions
Fe-α
(200)
80
90
100
110
120
2 Theta
*K. Shetty, S. Kumar, P. Raghothama Rao, Surface & Coatings Technol., 203 (2009) 1530-1536
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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24. XRD analysis
INC-7 & INC-7N
γ (111)
u.a.
50
55
60
65
70
75
80
85
90
50
55
60
2 Theta
γ (2 0 0)
INC-7
INC-7N
γΝ (2 0 0)
CrN
γ (2 0 0)
γΝ (1 1 1)
INC-6
INC-6N
γΝ (2 0 0)
Fe4N
γ (111)
a.u.
γΝ (1 1 1)
INC-6 & INC-6N
65
70
75
80
85
90
2 Theta
γ phase is observed in the as received samples, whereas in the nitrided samples a
mixture of γ and γN phases is present*.
Fe4N is also formed in INC-6N and CrN is observed in INC-7N.
*S. Chollet et al., Surface & Coatings Technol., (2013) In press.
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 24

25. Wear (Room T)
K wear at room temperature
Pin-on-disc configuration
Counter ball: alumina; Ø = 6 mm
20000 cycles, 2N, 10 cm/s
R = 7, 9 and 11 mm
18
-14
3
m /Nm
15
Kwear x10
Wear test conditions
12
Sample
MAR-3
MAR-3 MAR-3N INC-6 INC-6N INC-7 INC-7N
0.099 ± 0.008
INC-7
0,1
0,0
14 ± 4
INC-6N
3
2.6 ± 0.2
INC-6
6
3.8 ± 0.5
MAR-3N
9
Kwear x10-14 m3/Nm
17 ± 2
INC-7N
0.094 ± 0.010
Sample
Nitrided maraging does not show an improvement on wear resistance whereas both
nitrided INCONEL alloys show an improvement of 2 orders of magnitude compared to
their respective non-treated samples.
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 25

26. Wear and COF (RT)
MAR-3
MAR-3N
Wear test conditions
Pin-on-disc configuration
Counter ball: alumina; Ø = 6 mm
20000 cycles, 2N, 10 cm/s
R = 7, 9 and 11 mm
INC-6
INC-6N
Sample
MAR-3
0.85 ± 0.05
INC-6
0.84 ± 0.06
INC-6N
0.86 ± 0.06
INC-7
0.67 ± 0.07
INC-7N
INC-7N
0.92 ± 0.07
MAR-3N
INC-7
COF
0.66 ± 0.04
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
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27. Wear and COF (RT)
MAR-3
INC-6
500 µm
500 µm
MAR-3N
INC-7
INC-7N
INC-6N
500 µm
500 µm
500 µm
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
500 µm
Page 27

28. Wear (at 450 ºC)
16
Wear test conditions
Pin-on-disc configuration
Counter ball: alumina; Ø = 6 mm
20000 cycles, 2N, 10 cm/s
10
8
Kwear x10
3
12
-14
m /Nm
14
6
4
2
0
MAR-3N
INC-6
INC-6N
INC-7
INC-7N
MAR-3
10.5 ± 1.0
MAR-3N
13.2 ± 1.0
8.2 ± 3.8
3.1 ± 0.3
INC-7
8.1 ± 2.0
INC-7N
MAR-3
Kwear x10-14 m3/Nm
INC-6N
Sample
Sample
INC-6
MAR-3 MAR-3N INC-6 INC-6N INC-7 INC-7N
2.7 ± 0.5
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 28

29. Wear (at 450 ºC)
MAR-3
MAR-3N
Wear test conditions
Pin-on-disc configuration
Counter ball: alumina; Ø = 6 mm
20000 cycles, 2N, 10 cm/s
INC-6
INC-6N
MAR-3N
shows
no
improvement compared
to the non treated MAR-3
INC-7
INC-7N
Nitrided INCONEL alloys
show
a
slight
improvement.
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 29

30. On going work
18
INC-7
14
N (atomic %)
When comparing with
other processes
(longer time, higher
temperature):
500 ºC, 1,5 h
480 ºC, 1,5 h
INC-7N
16
12
10
8
6
4
2
0
• 480 ºC – 1.5h
• 500 ºC – 1.5h
0
1
2
3
4
5
6
7
8
Depth (microns)
Nanoindentation results
are similar at high loads,
despite
the
thicker
nitrided layers of the
above
mentioned
processes.
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
500 ºC, 1,5h
480 ºC, 1,5h
INC-7N
INC-7
Page 30

31. On going work
MAR-3
MAR-3N
500 ºC -1.5h
480 ºC -1.5h
Sample
Kwear x10-14 m3/Nm at RT
MAR-3
3.8 ± 0.5
MAR-3N
2.6 ± 0.2
480 ºC-1.5h
1.4 ± 0.5
500 ºC-1.5h
Kwear x10-14 m3/Nm at 450 ºC
MAR-3
10.5 ± 1.0
MAR-3N
13.2 ± 1.0
480 ºC-1.5h
8.1 ± 0.8
500 ºC-1.5h
7.9 ± 0.5
15
10
5
2.1 ± 0.3
Sample
N (atomic %)
20
0
0
10
20
30
40
50
60
70
80
Depth (microns)
When comparing with other processes
(longer time, higher temperature):
• 480 ºC – 1.5h
• 500 ºC – 1.5h
Longer profiles with higher nitrogen
concentration in the surface are obtained.
Tribological tests show a slight
improvement on wear resistance.
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 31

32. Outline
1. Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5.Summary
6. Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 32

33. Summary
Arc activated plasma nitriding processes have been carried out for the nitriding
of a series of high nickel content alloys (Maraging 300, INCONEL 600 and
INCONEL 718).
Chemical, mechanical, microstructural and tribological analysis of the non
treated and nitrided samples has been done.
Maraging steel 300 has shown long nitriding profiles. The formation of Fe
nitrides explains the superficial hardness increase.
INCONEL alloys 600 and 718 have shown short nitrogen profiles but with
nitrogen concentrations up to 14-15%. The formation of γN phase and Fe4N
(INC-6N) and CrN (INC-7N) compounds permits to improve wear resistance of
both alloys 2 order of magnitude at room temperature.
Longer and higher nitrogen profiles are possible to obtain when varying different
process parameters (temperature, time,…)
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 33

34. Outline
1. Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6.Future work
7. Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 34

35. Future work
Characterization of corrosion properties of
nitrided samples
EBSD characterization of nitrided samples
Optimization of the nitriding process for each
alloy
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding

36. Outline
1. Introduction
2. Objectives
3. Methodology
4. Characterization: Results and discussion
5. Summary
6. Future work
7.Acknowledgments
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 36

37. Acknowledgments
The authors would like to thank to the Departamento
de Innovación y Empleo of Gobierno de Navarra for
their support in Super-Maraging project.
Thank you for your kind attention!
Mechanical, Structural and Tribological Characterisation of High Nickel Content Alloys before and after
Arc Activated Plasma Nitriding
Page 37