1. technology and computing

INDUSTRIAL MATERIALS
Coated SUMIBORON BNC2010/BNC2020 for
Hardened Steel Machining Realizing Long and
Stable Tool Life
Yusuke MATSUDA*, Hironari MOROGUCHI, Nozomi TSUKIHARA,
Katsumi OKAMURA, Makoto SETOYAMA and Tomohiro FUKAYA
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------In the automotive industry, a trend is seen that in line with the acceleration of automakers’ transferring production to
developing countries, an increasing number of production lines are unmanned, or operated by a small number of people. For
that reason, there are strong demands for cutting tools having long and stable tool life. To satisfy such demands, we have
developed Coated SUMIBORON BNC2010/BNC2020. Compared with conventional cutting tools, Coated SUMIBORON
BNC2010 has improved in notch-wear resistance and achieves longer tool life, even in high-precision cutting of strict surface
roughness criteria. BNC2020 has improved in breakage resistance and peeling resistance of the coating layer and achieves
longer and more stable tool life in continuous and interrupted machining. This report describes the advantages and cutting
performance of BNC2010/BNC2020.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Keywords: PCBN, hardened steel, high precision cutting, interrupted cutting, PVD coating
1. Introduction
2. Issues in Hard Turning
Cubic boron nitride (CBN)* has hardness and
thermal conductivity second only to diamond, and has
low reactivity with ferrous metals. Sumitomo Electric
Hardmetal Corporation succeeded in developing the
world’s first CBN tool for the machining of hardened
steel parts by sintering a mixture of CBN particles and a
special ceramic binder, and launched it on the market in
1977 under the trade name SUMIBORON. Since the
release in 2000 of Coated SUMIBORON, which features
higher wear resistance by ceramic coating on the CBN
sintered body with PVD*2 technology, higher-precision
and higher-efficiency machining have been realized.
The shift from grinding to cutting, has contributed to
productivity improvement and cost reduction, mainly in
the automotive industry.
In the automotive industry, a trend is seen that, in
line with the acceleration of automakers’ transferring
production to developing countries, an increasing
number of production lines are unmanned, or operated
by a small number of people. For that reason,
customers' demands for cutting tools have shifted from
“high-efficiency cutting” to “long and stable tool life.”
Furthermore, the requirement for high-precision cutting
has become stronger against the background of an
increase of high-functional automotive parts. To satisfy
such demands, we have developed Coated
SUMIBORON BNC2010 and BNC2020, which achieve
considerably longer and more stable tool life than the
conventional Coated SUMIBORON series. The advantages and cutting performance of BNC2010 and
BNC2020 are described below.
A coated CBN tool has a hard and tough CBN
sintered body covered with a ceramic coating having
excellent heat and oxidation resistance, as shown in Fig. 1.
As the result, it can achieve longer tool life, even in hard
turning where the cutting edge is subjected to high
load and heat during the cutting. However, the hardness
and toughness of a ceramic coating is lower than a CBN
sintered body, abrasive wear and coating peelings occur
in the case when the mechanical load is added at the
cutting edge. On the other hand, desired shape and
mechanical strength are given to the hardened steel
workpieces by applying appropriate forming, forging
and thermal treatments. However, surface integrity, such
as hardness, microstructure and stress state, may vary
among different lots and within the same lot, too.
Moreover, an overall tooling system, composed of a
lathe, a chuck and a holder, may not always has enough
rigidity to cut hardened steel. As the result, above abrasive wear or coating peeling may occur due to discontinuous load, and often cause shorter or more unstable
tool life.
1
Cross section of cutting edge
Coated CBN tool
Tool type： 2NC-CNGA120408
Ceramic coating
Edge preparation
CBN
sintered body
Fig. 1. Structure of Coated CBN tool
SEI TECHNICAL REVIEW · NUMBER 80 · APRIL 2015 · 85
Figure 2 shows classification of the failure mode in
hard turning. In the case of high-precision cutting with
the required surface roughness of less than Rz 3.2*3, the
feed rate is often set low for the superior theoretical
surface roughness. As a result, the notch wear is increased
by the focused mechanical load on the end-cutting edge
of the notch where the thickness of the chip becomes
thin. In such high-precision cutting, suppression of the
notch wear is most important because it is transcribed on
the machined surface and it becomes a deciding factor of
the surface roughness, as shown in Fig. 3. In the case of
general purpose, breakage from crater wear and chippings from coating peeling become the main failure
mode because of the high feed rate, high depth of cut,
or interruptions.
Criteria of surface roughness
Rz（µm）
14
General purpose
Crater → Breakage
12
Coating peeling
10
8
6
High-precision
4
2
Notch wear
0
0
10
20
30
Efficiency Vc（m/min）・f（mm/rev.）
Fig. 2. Failure mode for hard turning
Edge
SEM image
f
Notch wear
Previous edge
Table 1. Specifications of BNC2010 and BNC2020
Application
Grade
BNC2010
BNC100
BNC160
BNC2020
BNC200
High
precision
General
CBN sintered body
CBN content CBN grain
Binder
size（µm）
（%）
50-55
2
TiCN
40-45
1
TiN
60-65
3
TiN
70-75
5
TiN
65-70
4
TiN
Ceramic coating
Composition
TiCN+Unique multi layer
TiAlN+TiCN
TiAlN+TiCN
TiAlN+Unique adhesion layer
TiAlN
Tickness
（µm）
1.5
2
2
1.5
2
Table 2. Physical properties of BNC2010 and BNC2020
Application
High
precision
General
Grade
BNC2010
BNC100
BNC160
BNC2020
BNC200
Hardness
Strength
HV（GPa） TRS（GPa）
30-32
1.10-1.20
29-32
1.05-1.15
31-33
1.10-1.20
34-36
1.20-1.30
33-35
1.15-1.25
Toughness
K1C（MPa・m1/2）
5.5-6.0
5.0-5.5
6.0-6.5
7.0-7.5
6.5-7.0
Thermal conductivity
（W/m・K）
40-60
40-60
55-75
65-85
60-80
physical properties of these grades. The CBN content,
particle size, and binding material are optimized and
controlled, depending on the applications, to provide
the CBN sintered body with the desired breakage and
wear resistances.
Figure 4 shows the micro structure of the CBN
sintered body of BNC2010 and BNC2020. Both have
improved in wear and breakage resistances by extremely
decreasing impurities which causes wear and cracks.
Furthermore, BNC2010 shows high wear resistance in
the cutting from high-speed to light interruption by
applying a high-purity titanium carbonitride (TiCN)
binder with excellent heat resistance. BNC2020 has
improved in thermal conductivity and toughness by
applying a larger size of CBN particles than conventional CBN grades and a high-purity titanium nitride
(TiN) binder.
Surface roughness
Rz
Machined
Notch wear surface
Conventional
cBN
Fig. 3. Relationship between notch wear and surface roughness
Ceramics
binder
Issues of impurities
Impurities
Less toughness
Less heat
resistance
BNC2010/BNC2020
BNC2010 for high-precision cutting is able to maintain superior surface finish by suppressing notch wear.
BNC2020 has improved in breakage resistance and
peeling resistance of the coating layer, achieving a longer
and more stable tool life under various cutting conditions. As a result, BNC2010 and BNC2020 eliminate tool
change at irregular intervals, making unmanned operations possible over a longer time, and realizing significant progress in both productivity improvement and
machining cost reduction.
3. Features of BNC2010 and BNC2020
3-1 Characteristics of BNC2010 and BNC2020
Table 1 shows the specifications of BNC2010,
BNC2020 and conventional grades. Table 2 shows the
cBN
Flank
Wear
Progress cracks
→ Breakage
High-purity binder
High toughness
High heat resistance
Fig. 4. CBN sintered body of BNC2010 and BNC2020
Ceramic coating can add various functions to the
cutting tool by design of its composition, thickness and
structure of coating layer. Figure 5 shows the cross
section view of BNC2010 and BNC2020 coatings.
BNC2010 has a trilaminar structure of a TiCN layer and
unique multi-layer that shows excellent notch wear
resistance. BNC2020 has a titanium aluminum nitride
(TiAlN) layer and unique adhesion layer that shows
86 · Coated SUMIBORON BNC2010/BNC2020 for Hardened Steel Machining Realizing Long and Stable Tool Life
■BNC2020
1.5 µm
TiN
7
1.5 µm
6
TiN
TiCN
Rz (µm)
■BNC2010
Unique multi
TiCN
TiAlN
Unique multi
TiCN
5
BNC100
4
3
BNC2010
2
1
Unique multi
Unique adhesion
CBN sintered body
0
0
CBN sintered body
2
4
6
8
Cutting length (km)
10
SCM415 HRC 58-62 (Continuous cutting)
4NC-DNGA150408
Vc = 160m/min, f = 0.08 mm/rev., ap = 0.1 mm, WET
Fig. 5. Coating structure of BNC2010 and BNC2020
Fig. 7. High-precision cutting evaluation results of BNC2010
Failure mode
at 8.0 km
BNC2010
BNC100
Small notch wear
Large notch wear
Profile
Surface roughness
excellent wear and coating peeling resistances, and realized stable coating during cutting.
3-2 Edge preparation of BNC2010 and BNC2020
BNC2010 and BNC2020 have two types of edge
preparations as shown in Fig. 6. “Standard” is for general
purpose and “HS” is a stronger type. By using appropriate edge preparation for each application, BNC2010
and BNC2020 can be used for various hard turning,
which covers a wide range of machinability and shape
of workpiece. “Standard”, with a good balance between
sharpness and breakage resistance, is the first recommendation for general cutting. By using “HS”, the
breakage in interrupted cutting could be suppressed by
larger chamfer angle and width.
Rz: 3.5 µm
Rz: 6.4 µm
Fig. 8. Comparison of BNC2010 with conventional CBN
Standard
HS
Standard
BNC2020
HS
Sharpness
better
BNC2010
Standard
α
25
30
25
35
W
0.12
0.17
0.12
0.27
Honing
Yes
Yes
Yes
Yes
Chamfer width W
BNC2020
HS
Cross section
of cutting edge
In case of
Breakage
Breakage resistance
better
Honing
Chamfer angle
α
BNC2020 (5.0 km)
BNC200
Fig. 6. Edge preparation of BNC2010 and BNC2020
BNC200 (3.0 km)
Competitor’s
CBN
4. Cutting Performance of BNC2010 and
BNC2020
4-1 High-precision cutting evaluation of BNC2010
Figure 7 shows the results of a comparison of
BNC2010 with conventional BNC100 in continuous
cutting of case hardened steel. BNC2010 achieved a
twice longer tool life by maintaining a lower surface
roughness than BNC100 in the case of the required
surface roughness of Rz 3.2. Figure 8 shows the results
of a comparison of the failure mode and machined
surface after 8 km of cutting of these 2 grades. It seems
that the notch wear of BNC2010 was smaller than that
of BNC100 and the surface roughness became better.
4-2 Interrupted cutting evaluation of BNC2020
Figure 9 shows the results of a comparison of
BNC2020 with conventional BNC200 and a competi-
0
1
2
3
Tool life (km)
4
5
SCM415 HRC 58-62 (Interrupted cutting)
4NC-CNGA120412
Vc = 130 m/min, f = 0.1 mm/rev., ap = 0.6 mm, DRY8
Competitor’s CBN
(2.5 km)
Fig. 9. Interrupted cutting evaluation results of BNC2020
tor’s CBN in interrupted cutting by using a case hardened steel workpiece with 5 V-shaped grooves. The
criteria of tool life was the breakage size of 0.2 mm.
BNC2020 achieved 1.8 times longer tool life than
BNC200 and 3 times more than the competitor’s CBN. It
seems that BNC2020 achieved the longest tool life of
the 3 grades because of its higher toughness.
SEI TECHNICAL REVIEW · NUMBER 80 · APRIL 2015 · 87
4-3 Coating peeling evaluation of BNC2020
Figure 10 shows the result of a coating peeling
evaluation of BNC2020, conventional BNC200 and a
competitor’s CBN in accelerated cutting condition in
which the cutting edge was repeatedly contacted to
the case hardened steel workpiece. Comparing the
average of the peeling areas after 1,000-time contacts
repeated 3-time tests for each grade, the peeling area
of BNC2020 is one-third of BNC200 and one-sixth of
the competitor’s CBN. BNC2020 shows excellent
coating peeling resistance due to the effect of its unique
adhesion layer.
5. Application Range of BNC2010
and BNC2020
Figure 12 shows the application range of Coated
CBN grades in hard turning. BNC2020 is a general
purpose grade which can use in a wide range from
continuous to medium interrupted cutting. In the case
of heavy interrupted cutting, conventional BNC300 is
the first recommendation. BNC2010 can be applied
from continuous to light interrupted cutting, and especially shows excellent performance in high-precision
cutting, such as a required surface roughness of less
than Rz 3.2.
BNC2020
Peeling area = 11340 µm2
Cutting speed
Vc (m/min)
BNC200
BNC200
BNC2010
300
Peeling area = 639 µm2
BNC2020
BNC2020
200
120
100
BNC300
50
Competitor’s CBN
Competitor’s
CBN
Peeling area = 20293 µm2
0
10000
Degree of
interruption
Continuous
0%
20000
Peeling area (µm 2)
Light
25%
Medium
50%
Heavy
100%
Bolt hole end
face, etc.
Spline shaft
outside diameter
Workpiece example
SCM415 HRC 58-62 (Inching cutting)
4NC-CNGA120412WH
Vc = 150 m/min, f = 0.2 mm/rev., ap = 0.2 mm, WET
Ratio of
interruption
No interruption
Fig. 10. Coating peeling evaluation results of BNC2020
About several
oil holes
Load to cutting edge
Large
Fig. 12. Application range of Coated CBN
4-4 Continuous cutting evaluation of BNC2020
Figure 1 1 shows the results of a comparison of
BNC2020 with conventional BNC200 in continuous
cutting of case hardened steel. BNC2020 achieved 1.5
times longer tool life than BNC200 in the case of the
required surface roughness of Rz 3.2. Comparing these
failure modes after 3-km cutting, BNC2020 had smaller
notch wear than BNC200 and showed better surface
roughness. It seems that the coating of BNC2020 at the
notch was maintained by the effect of unique adhesion
layer and worked to suppressing notch wear.
at 3 km
BNC2020
6. Cutting Example of BNC2010 and
BNC2020
Figures 13–17 show the application example of
BNC2010 and BNC2020.
Figure 13 is a high-precision cutting by BNC2010.
It with WH-wiper achieved long and stable tool life,
even in the case of a surface roughness requirement of
Rz 1.6.
CVJ outer race face turning
BNC2020
Criteria: Rz 1.6 μm
Material: S53BC (HRC 58-63)
Vc = 150 m/min, f = 0.2 mm/rev
ap = 0.2 mm, DRY
4NC-CNGA120412WH
BNC200
BNC200
0
1
2
3
4
5
6
Workpiece number
0
(pcs)
7
Tool life (km)
BNC2010
Criteria: Rz = 3.2 µm
SCM415 HRC58-62 (Continuous cutting)
4NC-DNGA150408
Vc = 130 m/min, f = 0.1 mm/rev., ap = 0.2 mm, WET
Notch wear
Fig. 1 1. Continuous cutting evaluation results of BNC2020
BNC100
200
400
600
Rz: 0.9 µm
800
700 pcs
(4.0 km)
400 pcs
Fig. 13. Application example 1 of BNC2010
88 · Coated SUMIBORON BNC2010/BNC2020 for Hardened Steel Machining Realizing Long and Stable Tool Life
Figure 14 is a high-precision cutting by BNC2010
with a surface roughness requirement of Ra0.6, nearly
equal to Rz 3.2. It maintained a low surface roughness
and achieved more than twice a longer tool life than the
conventional CBN grade.
Figure 15 is interrupted cutting by BNC2020. It
achieved 1.5 times longer tool life than conventional
CBN grade. Furthermore, BNC2020 with HS-type edge
preparation showed greater breakage resistance and
could continue to cutting over 300 pcs.
Sun gear carburized layer removal machining
Main shaft outer diameter turning
Criteria: Ra 0.6 μm
Material: 20NiCrMo2-2
Vc = 200 m/min,
f = 0.1 mm/rev
ap = 0.35 mm, DRY
4NC-DNGA150408
BNC2010
: 80 pcs
(5.7 km)
0.9
BNC100: 35 pcs
Ra（µm）
0.8
0.7
Competitorʼs
CBN: 50 pcs
BNC160
: 26 pcs
0.6
0.5
Criteria
0.4
0.3
0
20
40
60
because of using a low rigidity lathe. BNC2020 achieved
twice a longer tool life than the conventional CBN grade
by suppressing coating peelings.
As described above, BNC2010 enables longer tool
life in high-precision cutting by maintaining low surface
roughness. BNC2020 realizes longer and more stable
tool life with higher reliability against breakage and
coating peeling in various cuttings, like interrupted or
high-load cutting.
80
100
Criteria: Dimension
Material: SCR420 (HRC 60)
Vc = 100 m/min
f = 0.15 mm/rev
ap = 0.5mm, WET
4NC-CNGA120408
Workpiece number 0
(pcs)
100
200
300
BNC2020
300 pcs
BNC200
200 pcs
Competitorʻs
CBN
100 pcs
BNC2020: 300 pcs
BNC200: 200 pcs
Workpiece number (pcs)
Fig. 14. Application example 2 of BNC2010
CVJ cage outer finishing
Criteria: Ra 0.8 μm
Material: 21NiCrMo2 (HRC 60)
Vc = 120 m/min
f = 0.1 mm/rev
ap = 0.15 mm, DRY
4NC-TNGA160420
Workpiece number 0
(pcs)
100
200
300 pcs
continuing
ø54
300 pcs
BNC2020
BNC2020 HS: 300 pcs
Hub outer diameter / face turning
300
BNC2020 HS
BNC200
Fig. 16. Application example 2 of BNC2020
200 pcs
BNC200: 200 pcs
Workpiece number 0
(pcs)
Criteria: Ra 1.6 μm
Dimensional accuracy 19 μm
Material: S58C (HRC 58-60)
Vc = 105 m/min
f = 0.12 mm/rev
ap = 0.2 mm, WET
4NC-DNGA150412N-SV
500
250
BNC2020
240 pcs
BNC200
BNC2020: 490 pcs
490 pcs
(18.7 km)
BNC200: 240 pcs
Fig. 15. Application example 1 of BNC2020
Coating peeling
Figure 16 is a carburized layer removal machining
by BNC2020, which was a very hard application because
of the tough cutting conditions like 0.5 mm of ap (depth
of cut) for eliminating the hardened layer. BNC2020
achieved 1.5 times longer tool life than the conventional
CBN grade, and 3 times longer tool life than the competitor’s CBN grade.
Figure 17 is a continuous cutting by BNC2020. In
this application, coating peelings were the main issue
Fig. 17. Application example 3 of BNC2020
7. Conclusion
By using BNC2010 and BNC2020, longer and
more stable tool life can be achieved in hard turning. It
is expected that the use of BNC2010 and BNC2020
accelerates improvement in tool life making significant
SEI TECHNICAL REVIEW · NUMBER 80 · APRIL 2015 · 89
contributions to productivity improvement and cost
reduction.
• ‌SUMIBORON is a trademark or registered trademark of
Sumitomo Electric Industries, Ltd.
＊ 1CBN
Technical Terms
(cubic boron nitride): Has hardness and thermal conductivity second only to diamond, and has
low reactivity with ferrous metals.
＊ 2PVD (physical vapor deposition): A coating method
using physical reaction
＊ 3
Rz (ten point average roughness): A criterion of
surface roughness. Micrometer order.
References
(1)Harada et al., “Development of Coated cBN Sintered Tools,”
SEI Technical Review, No. 52, pp. 81–86 (2001)
(2)Teramoto et al., “Development of SUMIBORON BNC100 for
High-Speed Cutting and SUMIBORON BNC160 for Highprecision Cutting of Hardened Steel,” SEI Technical Review,
No. 66, pp. 93–100 (2008)
(3)Okamura et al., “Development of SUMIBORON NEW BNC200
for High-Efficiency Machining of Hardened Steel Parts,” SEI
Technical Review, No. 68, pp. 16–21 (2009)
(4)Harada et al., “Development of ‘SUMIBORON’ BN1000/
BN2000 for Hard Turning” SEI Technical Review, No. 72, pp.
100–106 (2011)
Contributors (The lead author is indicated by an asterisk (*).)
Y. MATSUDA*
• ‌Super Hard Materials Development
Department, Sumitomo Electric Hardmetal
Corp.
H. MOROGUCHI
• ‌Super Hard Materials Development
Department, Sumitomo Electric Hardmetal
Corp.
N. TSUKIHARA
• ‌Super Hard Materials Development
Department, Sumitomo Electric Hardmetal
Corp.
K. OKAMURA
• ‌Manager, Super Hard Materials
Development Department, Sumitomo
Electric Hardmetal Corp.
M. SETOYAMA
• ‌Super Hard Materials Development
Department, Sumitomo Electric Hardmetal
Corp.
T. FUKAYA
• ‌General Manager, Super Hard Materials
Development Department, Sumitomo
Electric Hardmetal Corp.
90 · Coated SUMIBORON BNC2010/BNC2020 for Hardened Steel Machining Realizing Long and Stable Tool Life