160 · New PVD-Coated Carbide Grade AC1030U for Precision Turning

INDUSTRIAL MATERIALS

1. Introduction

Among the indexable insert grades used for cutting tools, those with hard ceramics coated over a cemented carbide substrate (hereinafter referred to as coated grades) are increasingly being used. They now account for more than 70% of all indexable insert grades because of their good balance between wear resistance and fracture resis-tance compared to other tool grades.(1)

Work materials that are machined using coated grades include various steel materials, such as carbon steel, alloy steel, stainless steel, and cast iron. In recent years, the competition for energy saving and fuel efficiency has been increasingly intensified, particularly in the automotive industry. The automotive components have therefore become smaller and lighter, whereas work materials have become more diversified.

Consequently, high performances are required for cutting tools, particularly for those used in precision machining of small components. These cutting tools should be versatile, capable of cutting a wide range of work mate-rials such as steel, stainless steel, heat-resistive steel, and pure iron, and have a good finishing performance to meet the requirements of finished surface precision. The conven-tional cutting tools hardly satisfy these requirements, and they need frequent replacement because tools need to be changed depending on the materials to be machined. Moreover, their life is short, which eventually causes a decrease in productivity.

To address these issues, we have developed AC1030U, a physical vapor deposition (PVD)*1 coated grade for precision machining, by applying the new PVD-coating technology “Absotech Bronze.” We have also added to our lineup the FYS-type grinded chip breaker for fine finishing. The background of their development and their performance, with examples of applications, are described in the following sections.

2. Issues of Precision Machining of Small Components

According to the survey, more than 70% of the factors that determine tool life in precision machining of small components are related to finished surface appearance and accuracy problems, such as a clouded finished surface and insufficiently smooth surface, as shown in Fig. 1.

Figure 2 shows the relationship between damage to the tool and finished surface quality. The damage to the tool that is particularly related to finished surface quality occurs where the tool directly contacts the work material, which is indicated as “nose R” and “front notch” in the figure. In general, the progress of wear or the occurrence of abnormal damage at this nose R and front notch part, such as chipping and deposit, has an adverse effect on finished surface quality. The resulting blemished surface or worsened surface rough-ness often indicates the end of the tool life.

However, an enhanced finished surface quality is required in precision machining of small components. Shown in Fig. 3 are examples of indexable inserts for

New PVD-Coated Carbide Grade AC1030U for Precision Turning

Takato YAMANISHI*, Hiroki TAKESHITA, Shinya IMAMURA, Kazuhiro HIROSE and Haruyo FUKUI

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------In recent years, automotive components have become smaller and lighter due to the trend of energy saving and fuel efficiency. Accordingly, a wider variety of materials, including those difficult to cut, have been used for these components. Sumitomo Electric Hardmetal Corporation has developed the new coated carbide grade “AC1030U” by applying the new physical vapor deposition (PVD) coating technology “Absotech Bronze” and the new chip breaker “FYS type” that has excellent chip control and high wear resistance in fine finishing. AC1030U with high cutting edge quality and high wear resistance is a general grade used for precision turning. The new grade and chip breaker can satisfy the demand for cost reduction in precision machining for various materials such as alloy steels, carbon steels, stainless steels, heat-resistance steels, and pure iron.----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Keywords: cutting tool, coated carbide, PVD

Finishedsurfacequality(burr, gloss)39%

Finishedsurface

roughness32%

Dimensional accuracy

10%

Wear resistance

6%

Chipping3% Others

10%

Fig. 1. Factors for tool life in precision machining of small components

SEI TECHNICAL REVIEW · NUMBER 84 · APRIL 2017 · 161

precision machining and the relationship between cutting edge quality and finished surface quality. Cutting edge quality may be affected by the existence of a minute chip-ping of a coating film at the nose R part or undulation in the cutting edge at the front notch part, prior to the use of the tool. These conditions can prevent the tool from satis-fying the required standard for finished surface quality, even at the initial stage of machining, or otherwise its life will be shortened.

3. Development of and New Technology for AC1030U

Figure 4 shows our lineup of PVD-coated grades for precision to finish machining. The span from low-speed precision machining to high-speed finish machining is covered by conventional grades (ACZ150, AC520U, AC6040M) and by the newly developed AC1030U. ACZ150 covers the low-speed range in precision machining, AC520U comprises the high-speed range in precision to finish machining, while AC6040M is particularly applied in the rough to finish machining of stainless steel. The new AC1030U is a PVD-coated grade covering a wide range in precision machining, from low- to medium-speed.

3-1 Development target of AC1030UIn order to define the development target for

AC1030U, an analysis was performed on the damage to used inserts of conventional PVD grades at their actual precision machining site. It was determined that, even though conventional grades were excellent both in wear resistance and in performance against the worsening of finished surface quality caused by the progress in wear, they were likely to worsen the finished surface quality at the initial stage of machining.

Consequently, the development targets for AC1030U included a wear resistance equivalent to or better than that of conventional grades used for machining the typical work materials in small automotive components, such as alloy steel, stainless steel, heat-resistive steel, and pure iron. Furthermore, AC1030U should provide the best finished surface quality at the initial stage of machining among all indexable insert grades used for precision machining that are available in the market. Thus, efforts were made to improve the tool cutting edge quality, which significantly affects the finished surface quality at the initial stage.

3-2 Development of AC1030UAC1030U uses a dedicated cemented carbide

Finished surface: Good Finished surface: Worsened

Cutting edge

Work material

Feed rate f

Front notch

Feeddirection

Nose R Finishedsurface

Surf

ace

roug

hnes

s RzUnblemished finished surface

Small surface roughness RzDamage to the nose R → BurrDamage to the front notch→ Large surface roughness

Surf

ace

roug

hnes

s Rz

Burr

Cutti

ng e

dge

and

finish

ed su

rfac

e qu

ality

Finished surface: Good Finished surface: Worsened

Exam

ple

of in

dexa

ble

inse

rts f

or p

reci

sion

mac

hini

ng

Rake face(Polished)

Flank face (b)Front notch

Undulated edge

Cutti

ng e

dge

at th

e no

se R

Smooth edgeCutti

ng e

dge

at

the

fron

t not

ch

Coating chipping No coating chipping

10 μm

Rake face

Flank face

Rake face

Flank face 10 μm

Flank faceFrontnotch

Rake face

Flank face

Rake face

Frontnotch

(a)Nose R

(a)

(b)

ndul

e

Fig. 2. Relationship between damage to the tool and finished surface quality

Fig. 3. Relationship between cutting edge quality and finished surface quality

50

100

150

200

Cutti

ng sp

eed

(m/m

in)

ACZ150

AC520U

AC6040M

AC1030U

Precisionmachining

Finishmachining

Fig. 4. AC1030U application range

162 · New PVD-Coated Carbide Grade AC1030U for Precision Turning

substrate and employs our original PVD coating tech-nology Absotech Bronze. Figure 5 shows the structure of AC1030U. The PVD coating makes use of our originally developed high adhesion technology, excellent in peeling resistance. It also adopts not only an ultra-multilayer thin coating structure, excellent in wear resistance, but also a smooth layer at the top surface to suppress chipping of the cutting edge coating, which significantly affects the finished surface quality. As shown in Fig. 6, this new coating has solved the coating-chipping problem seen in conventional grades.

In precision machining, the edge shape of an index-able insert is strongly affected by grinding. Therefore, compared with the conventional grade, the cutting edge surface roughness of AC1030U has been significantly improved with the new polishing technology, as shown in Fig. 7.

As shown in Fig. 8, this polishing quality improve-ment, in combination with the new PVD coating, prevented cutting edge undulation, and significantly improved the cutting edge quality.

3-3 Cutting performance of AC1030UFigures 9 to 11 show the cutting performance of

AC1030U by work material.Shown in Fig. 9 is the performance of AC1030U in

cutting alloy steel. It indicates that, with the improved cutting edge, AC1030U has achieved a fine finished surface compared with the conventional and competitor’s grades.

Figure 10 shows the performance in machining stain-less steel. It also points out that, with less wear volume, AC1030U has achieved a better finished surface roughness from the initial stage than the conventional and competi-tor’s grades.

Figure 11 shows the performance in processing heat-resistive steel. It indicates that, with less wear on the cutting face side, AC1030U has achieved a better finished surface compared with the conventional and competitor’s grades.

Regarding cutting performance for each work mate-rial, the cutting edge quality improvement obtained by the

Carbide substrate

Coating surface

1μm Tough carbide substrateGood chipping resistance

High hardness layerHigh wear resistance

Smooth surface layerImproved surface quality

High adhesion strengthExcellent peeling resistance

Coating chipping No coating chipping

AC1030UConventional

Cutti

ng e

dge

befo

re c

utting

20 μm

Coating chipping

AC1030UConventionalRz = 1.20 μm Rz = 0.65 μm

Fig. 5. Structure of AC1030U

Fig. 6. Cutting edge quality of AC1030U

Fig. 7. Polished cutting edge of AC1030U (uncoated)

Conventional

Competitor’s

AC1030U

0.6

0.8

1.0

1.2

1.4

1.6

0.2 0.4 0.6 0.8 1 1.2

Rake

face

surf

ace

roug

hnes

s Rz [μm

]

Flank face surface roughness Rz [μm]

Area without edge undulation

Fig. 8. Correlation between cutting edge surface roughness and edge undulation (coated)

AC1030UConventional Competitor’s

Work material: SCM435 Length of cut: 1200 mmCutting conditions: Vc = 50 m/min, f = 0.05 mm/rev, ap = 0.1 mm, Oil Inserts: DCGT11T302R-FY

Finished surfaceWor

km

ater

ial

Rake

face

Flan

kFa

ce

Fig. 9. Cutting performance of AC1030U (Alloy steel)

SEI TECHNICAL REVIEW · NUMBER 84 · APRIL 2017 · 163

new PVD coating and polishing technology has exerted the intended effect, and AC1030U has achieved wear resis-tance and finished surface quality equivalent to or even better than the conventional and competitor’s grades.

4. FYS Chip Breakers for Fine Finishing

In precision machining of small components made of low-carbon steel, pure iron, or other soft materials that are likely to adhere to the tool, chip control and material type determine the tool life and productivity. Our lineup of grinded chip breakers for precision machining includes the FY and FX types (for low-depth cut and low-speed feed), the W and SD types (for relatively near-finish machining), and the wiper-shaped SDW type, and currently the FYS type has been developed for fine finishing.

With a breaker width narrower than that of the existing chip breakers, the FYS chip breaker has an improved chip control performance, particularly for fine finishing with a feed distance of less than 0.05 mm/rev. and a depth of cut of less than 1.0 mm. Shown in Fig. 12 is the recommended use range of our grinded chip breakers. With

the FYS chip breaker added to the lineup, a wide range of machining is covered from fine to finish machining.

In addition, as shown in Fig. 13, the improved chip control of the FYS chip breaker suppresses wear on the cutting face in pure iron machining, thereby allowing for a longer tool life in fine finishing.

5. Application Examples of AC1030U

Figures 14 to 16 show examples of the AC1030U being used at actual production sites.

Shown in Fig. 14 is an actual example of steel machining with AC1030U. Even after twice as many pieces machined as by the conventional grade, AC1030U could still machine work materials with a stable surface quality, without any abnormal damage such as cutting edge chipping.

Figure 15 shows an actual example of AC1030U for stainless steel machining. Similarly, even after twice as many pieces machined as by the competitor’s grade, the work materials could be stably machined without any abnormal damage such as cutting edge chipping.

Figure 16 shows an actual example for pure iron machining. Even after 1.5 times as many pieces machined as by the conventional grade, the state of damage was stable without, for example, cutting edge chipping.

AC1030UConventional Competitor's

Finished surface

Work material: SUH310 Length of cut: 1200 mmCutting conditions: Vc = 100 m/min, f = 0.05 mm/rev, ap = 0.1 mm, Oil Inserts: DCGT11T302R-FY

Cutting edge

0

0.5

1

1.5

2

2.5

0 50 100

Fini

shed

surf

ace

roug

hnes

s Rz [

mm

]

Length of cut [m]

AC1030U

Competitor's

Conventional

Work material: SUS304 *Photos show length of cut = 100 mCutting conditions: Vc = 100 m/min, f = 0.05 mm/rev, ap = 0.1 mm, Oil Inserts: DCGT11T302R-FY

Dept

h of

cut

(mm

)

Feed rate (mm/rev)

FY chip breaker FYS chip breaker

Breakershape

Damage to the cutting edge

(L=1200m)

Chip

Breaker width: 2.5mm

Rake angle: 15o Rake angle: 15o

Breaker width: 1.0mm

Work material: Pure ironCutting conditions: Vc = 120 m/min, f = 0.02 mm/rev, ap = 0.8 mm, Oil Inserts: DCGT11T302R-FY,FYS

Crater wear width

Step: 1mmFig. 11. Cutting performance of AC1030U (Heat-resistive steel)

Fig. 10. Cutting performance of AC1030U (Stainless steel)Fig. 12. Recommended range for grinded chip breakers

Fig. 13. Cutting performance of FYS chip breaker

164 · New PVD-Coated Carbide Grade AC1030U for Precision Turning

6. Conclusion

AC1030U, with the new PVD coating technology “Absotech Bronze,” is a grade that offers both excellent finished surface quality and wear resistance in precision

machining. Equipped with the new FYS type chip breaker for fine finishing, AC1030U offers excellent performance in precision machining of a wide range of work materials such as steel, stainless steel, heat-resistive steel, and pure iron. Furthermore, AC1030U will significantly reduce machining costs and improve productivity in precision machining.

• Absotech Bronze is a trademark or registered trademark in Sumitomo Electric Industries, Ltd.

Technical Term＊1 Physical vapor deposition (PVD): A method for

physically depositing a thin film of a target material in its vapor phase onto the surface of a substrate.

Reference(1) Monthly report of JAPAN CEMENTED CARBIDE TOOL

MANUFACTURERS’ ASSOCIATION (2015)

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

T. YAMANISHI*• Hard Materials Development Department, Sumitomo

Electric Hardmetal Corp.

H. TAKESHITA• Engineering Department, Hokkaido Sumiden

Precision Co., Ltd.

S. IMAMURA• Assistant Manager, Hard Materials Development

Department, Sumitomo Electric Hardmetal Corp.

K. HIROSE• Group Manager, Hard Materials Development

Department, Sumitomo Electric Hardmetal Corp.

H. FUKUI• Assistant General Manager, Hard Materials

Development Department, Sumitomo Electric Hardmetal Corp.

Work material: Nozzle part (S45C)Inserts: DCGT070202MN-SIVc = 200 m/minf = 0.06-0.08 mm/revap = 0.1 mm Oil

Conventional AC1030U

Tool life: 1200 pcs/c Tool life: 2400 pcs/c

Φ10 Φ6

Competitor's AC1030U

Tool life: 800 pcs/c Tool life: 1600 pcs/c

Φ10

Work material: Sensor housing (SUS430)Inserts: DCMT11T304MN-FCVc = 50 m/minf = 0.06 mm/revap = 0.2 mm Oil

Conventional AC1030U

Tool life: 2000 pcs/c Tool life: 3000 pcs/c

Work material: AT plunger (Pure iron)Inserts: DCGT11T302R-FYVc = 110-147 m/minf = 0.05-0.07 mm/revap = 0.05-0.07 mm Oil

Φ15

Fig. 14. Application example of AC1030U (Steel machining)

Fig. 15. Application example of AC1030U (Stainless steel machining)

Fig. 16. Application example of AC1030U (Pure iron machining)