INDUSTRIAL MATERIALS

Turning Grades ‘AC5000S’ for Exotic Alloys
Shinya IMAMURA*, Keizo TANAKA, Shuhei MISUMI, Kazuhiro HIROSE,and Haruyo FUKUI---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Exotic alloys, such as nickel alloys, cobalt alloys, and titanium alloys, are widely used for equipment and parts in the aircraft andauto industries due to their superior heat and corrosion resistance. There has been a growing demand for the machining tools forthese alloys. When machined, exotic alloy work materials are likely to adhere to the edges of cutting tools, resulting in a sudden
fracture of the tools. These tools have a significantly shorter life than those used for general steel. Thus, demand is high for cutting
tools with stable performance and long tool life. The newly developed grades, AC5015S and AC5025S, are characterized by
improved wear and fracture resistance with a state-of-the-art physical vapor deposition coating and special cemented carbide.
These materials help reduce tool replacement frequency and tool consumption by extending tool life, thus contributing to thereduction of machining costs.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Keywords: difficult-to-machine material, cutting tool, PVD, stable performance and long tool life, high efficiency machining

1. Introduction
Regarding indexable inserts for cutting tools, theusage ratio of coated materials (cemented carbide alloybase metals coated with a hard ceramic film) has been
increasing year by year.
Compared to other tool materials, coated materials arecharacterized by an outstanding balance between wear
resistance and fracture resistance. At present, coated materials account for 70% of all indexable insert materials.
Recently, nickel (Ni)-based metals, cobalt (Co)-based
metals, titanium (Ti) alloys, and other materials are often
used for equipment and parts in the aircraft, oil and gas,
medical, and auto industries because they are characterized
by superb heat resistance and corrosion resistance. The
consumption of these materials is expected to increasesignificantly.
These materials are characterized by high temperaturestrength. When cutting these materials, they are likely to bewelded onto the cutting edge of a tool, resulting in significant reduction in the tool life due to sudden fracture of thecutting edge of the tool, among other factors.
Against this backdrop, demand for cutting tools withstable performance and long tool life has been increasing inorder to cut difficult-to-machine materials.
To meet such market needs, we have developed andmarketed two products. One is AC5015S, a new physicalvapor deposition (PVD)*1-coated material that achieves
long tool life and high efficiency machining when turning
difficult-to-machine materials, and the other is AC5025S, a
new coated material that achieves stable performance andlong tool life in interrupted machining.
This paper reports the development history andperformance of these materials.

2. Development Target for AC5015S and AC5025S
To identify issues in turning difficult-to-machinematerials, we collected used tools from the market andconducted in-depth analysis of the damage morphology.

The results are shown in Fig. 1. There were mainly
two types of damage to the cutting edge.

Plastic deformation 4%

Other
8%

Chipping 4%
Flank wear

Crater wear
34%

19%
Notch wear
31%

Fig. 1. Analysis of used tools

One was crater wear resulting from the abrasion ofinserts generated by chips, and the other was boundary
fracture that occurs near the area where the work material
comes into contact with the tool initially (Fig. 2). We foundthat these types of damage account for 65% of total
damage.
Thus, the target performance for AC5015S andAC5025S was to double the crater wear resistance andnotch wear resistance compared to our conventional materials.
Meanwhile, we also found that there was strong
market demand for high efficiency machining. Thus, we set
a target for AC5015S to achieve a tool life equivalent tothat of our conventional material under twice as high efficiency machining conditions as with the conventionalmaterial.

SEI TECHNICAL REVIEW · NUMBER 89 · OCTOBER 2019 · 43

film.

Crater wear

Notch wear

Flank wear

Fig. 2. Damage morphology on the cutting edge

3. Features of AC5015S and AC5025S
3-1 Efforts to improve crater wear resistance
To elucidate the mechanism of crater wear, we turned
Inconel*2 718, an Ni-based heat-resistant alloy (ourconventional coated material) and closely observed thecutting edge.
Notably, we cut the cutting edge in the initial stage(three minutes after the start of machining) on the A-A’cross section, as shown in Fig. 3, and observed it from thecross section direction.

Work material: Inconel718 (Ni55-Cr21at%)
Cutting conditions: Vc = 40 m/min, f = 0.2 mm/rev, ap = 1.5 mm, WET, T = 3 minBA

Welding

The high oxygen concentration is attributable to oxidization of the coating film due to heat generation during
cutting. It is necessary to improve the oxidization resistance of the coating film to reduce oxidization wear.
The high Cr concentration is attributable to diffusionof Cr contained in the work material into the coating film.
The composition of the coating film that was applied to theconventional material was AlTiCrN. Thus, both the work
material and the coating film contained Cr. This is considered to have increased the affinity of these materials andincreased the likelihood of welding of the work material on
the coating film. This is also considered to have promoted
diffusion wear due to diffusion of Cr in the work material
into the coating film.
To improve oxidization wear resistance and diffusion
wear resistance, we developed a new Cr-free AlTiSiN film.
Figure 4 shows the results of an oxidation test.
We created samples of cemented carbide alloy basematerials on which a conventional AlTiCrN film and thenewly developed AlTiSiN film were formed. The samples
were retained at 900°C in the atmosphere for 30 minutes,
and were observed from the cross section direction.
The oxidation layer thickness of the conventional
AlTiCrN film was 1.0 μm. Meanwhile, the oxidation layer
thickness of the newly developed AlTiSiN film was 0.4
μm. The oxidization resistance properties of the AlTiSiN
film were good, more than double that of conventional
AlTiCrN film.
We also turned Inconel 718 using a cutting edge
coated with the AlTiSiN film, and analyzed the composition of the crater wear area from the cross section direction
three minutes after the start of machining.
The results are shown in Fig. 5. No diffusion of Cr
was confirmed near the surface of the AlTiSiN film.

B’AA'Welding

Film(Al, Ti, Cr)N(Ni, Cr)

Thickness ofoxidation layer
0.4 µmThickness ofoxidation layer
1.0 µmCarbidesubstrate

Film
Carbide substrate

AlNiOCr(a) Conventional
AlTiCrN film

TiDiﬀusion of Cr near the ﬁlm surface(c) B-B’ Cross section
Fig. 3. Observation of damage at the crater wear from the cross section direction

We identified wear of the coating film on the face andwelding of the work material on the worn area. To conduct
in-depth analysis, we used energy dispersive X-ray spectrometry (EDX)*3 along B-B’ to analyze the composition.
We found that the concentration of oxygen (O) and chrome(Cr) was high in some areas near the surface of the coating

44 · Turning Grades ‘AC5000S’ for Exotic Alloys(b) Newly developedAlTiSiN film

Fig. 4. Results of observation of the cross section after oxidation test

Intensity (cps)Intensity (cps)Carbide substrate(b) A-A’ Cross section(a) Rake face

B

FilmB

Welding(Ni, Cr)

NiO

Film(Al, Ti, Si)N

Carbidesubstrate

AlCr

Ti
Si

N

Almost no Cr diﬀusion

Fig. 5. Results of composition analysis of the crater wear on the AlTiSiN film

18.0
Newly developed substrate(S10 grade)

Hardness Hv / GPa

17.5
17.0
16.5

Conventional grade(S10 grade)

15.5
15.0

6.5

7.5

Work material: Hastelloy
Insert: CNMG120408N-EX
Cutting conditions: Vc = 50 m/min, f = 0.1 mm/rev,
ap = 1.5 mm, WET

0.6
Conventional
grade

0.5
0.4

T = 37 min
Conventional
grade

AC5025S

0.3AC5025S

0.2
0.1
0

Conventional grade(S20 grade)

16.0

using AC5015S. The results are shown in Fig. 7. AC5015S
demonstrated a tool life that is double or more that ofconventional materials.
A similar evaluation was made on AC5015S byincreasing the cutting speed to 70 m/min. The results
showed that machining is possible for up to 13 minutes,
achieving high efficiency machining that is double that ofthe conventional material.
The boundary fracture resistance test of Hastelloy*4
was conducted using AC5025S. Figure 8 shows the results.
AC5025S demonstrated notch wear resistance that isdouble that of the conventional material.

Notch wear Vn / mm

3-2 Efforts to improve notch wear resistanceDuring cutting, there is a large difference in stressapplied between the areas where the work material comes
into contact (on the ridge line of the cutting edge) and thosewhere the work material does not. Fracture and wear are
likely to occur near the boundary.
Fracture is likely to occur at the boundary whenmachining difficult-to-machine materials whose hightemperature strength is high in particular. The tools must betough.
Against this backdrop, we worked to increase thestrength of the cemented carbide base metal to improve thenotch wear resistance.
We developed a new cemented carbide alloy byincreasing the strength of the WC raw materials, uniformly
granulating the WC raw materials, and improving thesintering conditions, in particular. As shown in Fig. 6, boththe S10 grade and S20 grade show fracture toughness values
1.2 times or higher than that of conventional materials.

Newly developed substrate(S20 grade)

8.50102030405060

Cutting time / minFig. 8. Results of evaluation of cutting Hastelloy using AC5025S

9.5

Fracture toughness K1C / MPa m1/2

Fig. 6. Characteristic value of carbide substrate

4. Examples of Machining Using AC5015S andAC5025S

T = 13 min

Work material: Inconel718
Insert: CNMG120408N-EX
Cutting conditions: Vc = 35 m/min, f = 0.1 mm/rev,
ap = 1.5 mm, WET

Flank wear Vb / mm

0.5
Conventional grade0.4

Conventional
grade

AC5015S

0.3
AC5015S

0.2
0.1
00102030
Cutting time / min

40Fig. 7. Results of evaluation of cutting Inconel 718 using AC5015SFigures 9 to 12 show examples of machining of heatresistant alloys using AC5015S and AC5025S by different
users.
The results of the machining of an aircraft part(Inconel 718) using AC5015S are shown in Fig. 9. The tool
life of AC5015S was double that of the competitor’sWork material: Inconel718 (Aircraft part)
Insert: SNMG120408N-EG
Cutting conditions: Vc = 50 m/min, f = 0.15 mm/rev,ap = 2.0 mm, WET
Number of machining (init/c)

3-3 Cutting performance of AC5015S and AC5025S
We commercialized AC5015S, which is derived fromthe combination of the AlTiSiN film and the S10 grade
substrate, and AC5025S, which is derived from the combination of the AlTiSiN film and the S20 grade substrate.
The wear resistance test of Inconel 718 was conducted100

Double tool life

50Competitorʼsgrade

AC5015SFig. 9. Example of machining using AC5015S ①

SEI TECHNICAL REVIEW · NUMBER 89 · OCTOBER 2019 · 45

product due to the excellent wear resistance.
Figure 10 shows the results of the machining of an
automotive part (Inconel 713C) using AC5015S. Under thehigh-speed conditions (cutting speed: 100 m/min.), the tool
life of AC5015S was double that of the conventional
product.
The results of the machining of an aircraft part(Inconel 718) using AC5025S are presented in Fig. 11. The
tool life of AC5025S was 1.7 times that of the conventional
product. The damage after machining was negligible.

Number of machining (init/c)

Work material: Inconel713C (Automotive part)
Insert: CNMG120408N-EX
Cutting conditions: Vc = 100 m/min, f = 0.12 mm/rev,
ap = 0.3 mm, WET

10Figure 12 shows an actual example of the machiningof an automotive part (Ni-based heat-resistant alloy) using
AC5025S. The tool life of AC5025S was double that of acompetitor’s product.

5. Conclusion
As discussed above, we developed a new PVD coating
film with superb wear resistance and a new cemented
carbide substrate with outstanding notch wear resistance,and applied them to AC5015S and AC5025S.
We succeeded in achieving stable performance andlong tool life (more than double that of conventional materials). These two materials will contribute greatly toreducing the cost of machining and improving productivity
in turning difficult-to-machine materials.

Double tool life

5＊1

AC5015S

CompetitorʼsgradeFig. 10. Example of machining using AC5015S ②Work material: Inconel718 (Aircraft part)
Insert: DNMG150408N-EG
Cutting conditions: Vc = 35 m/min, f = 0.1 mm/rev,
ap = 1.6 mm, WET

Conventional grade(1.5 unit/c)

AC5025S(2.5 unit/c)

Fig. 11. Example of machining using AC5025S ①

Work material: Ni based heat resistance alloy (Automotive part)
Insert: TNGG160402N-SU
Cutting conditions: Vc = 70 m/min, f = 0.1 mm/rev,
ap = 0.15 mm, WETCompetitorʼs grade(100 unit/c)

AC5025S(200 unit/c)

Fig. 12. Example of machining using AC5025S ②

46 · Turning Grades ‘AC5000S’ for Exotic Alloys

＊2＊3

＊4

Technical Terms

Physical vapor deposition (PVD): A target material isionized by arc discharge or other means and reactedwith a gas to allow the gas to deposit on the basematerial as a ceramic film.
Inconel: A type of Ni-based heat-resistant alloy. It is a
registered trademark of Special Metals Corporation.
Energy dispersive X-ray spectrometry (EDX): Atechnique to measure elements that constitute anobject and their concentration based on characteristic
X-ray that is generated when an electron beam or
X-ray is irradiated on an object.
Hastelloy: A type of Ni-based heat-resistant alloy. It
is a registered trademark of Haynes International, Inc.

Contributors The lead author is indicated by an asterisk (*).

S. IMAMURA*• ‌Manager, Sumitomo Electric Hardmetal Corp.

K. TANAKA• ‌Assistant Manager, Hardmetal Division

S. MISUMI• ‌Sumitomo Electric Hardmetal Corp.

K. HIROSE• ‌Manager, Sumitomo Electric Hardmetal Corp.

H. FUKUI• ‌Assistant General Manager, Sumitomo ElectricHardmetal Corp.

SEI TECHNICAL REVIEW · NUMBER 89 · OCTOBER 2019 · 47