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Highly wear-resistant cutting tools with textured surfaces in steel cutting
CIRP Annals - Manufacturing Technology 61 (2012) 571–574
Contents lists available at SciVerse ScienceDirect
CIRP Annals - Manufacturing Technology jou rnal homep age : ht t p: // ees .e lse vi er . com /ci r p/ def a ult . asp
Highly wear-resistant cutting tools with textured surfaces in steel cutting Toshiyuki Enomoto (2)*, Tatsuya Sugihara, Satoshi Yukinaga, Kenji Hirose, Urara Satake Department of Mechanical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords: Cutting tool Surface Texture
To increase cutting tool life, our previous studies have proposed cutting tools with nano-/micro-textured surfaces, which displayed high anti-adhesive effects in the cutting of aluminum alloys. In this study, the previously developed tools were used to cut steel materials with the goal of improving wear resistance. However, a serious problem regarding the wear still remained. Therefore, to overcome this problem, new TiAlN-coated cutting tools with periodical stripe-grooved surfaces were developed. Face-milling experiments on steel materials showed that the new texture and coating on the tool surface significantly reduce the tool wear. ß 2012 CIRP.
1. Introduction In cutting processes, the improvement of anti-adhesive properties and wear resistance of cutting tools are constantly and strongly required to increase the tool life. Therefore, many cutting tool technologies pertaining to material, geometry, surface coating, and surface finishing have been developed [1]. However, the technologies cannot meet recent requirements in practical processes, especially in steel cutting, because the high mechanical stress and heat generated on the tools’ surfaces result in significant tool wear. To improve cutting tool properties, we adopted a surface engineering approach [2,3], namely, a functionalization of tool surfaces by textures [4]. In our previous study [5], we developed diamond-like carbon-coated cutting tools with nano-/microtextured surfaces to determine the role of the faces of the textured tool rake on the retention of the cutting fluid and the decrease in the contact area between the tool surface and chip. Face-milling experiments on aluminum alloys showed that textured surfaces significantly improve the lubricity and anti-adhesive properties at the tool–chip interface. In this study, the previously [5] developed tools with nano-/ micro-textured surfaces were applied to the cutting of a carbon steel material (S53C) with the aim of improving tool wear resistance. Based on our findings, we developed a cutting tool with a periodical stripe-grooved surface to improve the desired wear resistance. In addition, we evaluated the corresponding cutting performance. 2. Nano-/micro-textured cutting tool surfaces 2.1. Cutting tools with nano-/micro-textured surfaces In a previous study [5], cutting tools with nano-/micro-textured surfaces were developed by laser-induced periodic surfacestructuring technology [6]. The irradiation of linearly polarized
* Corresponding author. 0007-8506/$ – see front matter ß 2012 CIRP. http://dx.doi.org/10.1016/j.cirp.2012.03.123
femtosecond laser pulses on a surface induces interference between the incident laser pulses and surface-scattered light or plasma waves on the surface. Precise and regular grooves are selforganized with the spacing of regular structures being either the same or smaller than the laser wavelength. Fig. 1 shows a schematic illustration, a scanning electron microscope (SEM) (JEOL Ltd., JSM-5800A) image, and atomic force microscope (AFM) (Pacific Nanotechnology Inc., Nano-R2) images of the cutting tool [5]. As shown in this figure, regular grooves that are 100–150 nm deep and 700 nm apart were generated on the tool rake face as sine waves. The grooves formed were orthogonal to the chip flow direction, i.e., parallel to the main cutting edge, to obtain good cutting properties [5]. Before laser irradiation, the tool rake face was polished with diamond slurry to obtain a surface roughness of 40 nm (peak to valley). 2.2. Cutting experiment procedures and cutting tool performance Cutting experiments involving both a cutting tool with a polished surface and the previously developed cutting tool were conducted on carbon steel S53C using a vertical machining center (Yamazaki Mazak Corp., AJV-18). The experimental setup is illustrated in Fig. 2. The center of the cutter was set on the center line of the workpiece. Table 1 lists the cutting conditions. A cemented carbide tool (Sumitomo Electric Hardmetal Corp., SEKN42MT) with a 100-mm-wide chamfer was used as the cutting tool insert. An emulsion-type cutting fluid (NEOS Co., Ltd., Finecut CFS-100) was supplied at a flow rate of 12.6 L/min. After cutting, rake faces of the cutting tools were measured using a two/three-dimensional stylus-type profile instrument (Kosaka Laboratory Ltd., SE3500K). Fig. 3 shows the threedimensional profiles and the sectional profiles of the rake faces of the polished tool and the previously developed cutting tool after cutting for 300 m. As shown in this figure, severe crater wear occurred on the rake faces of both the polished tool and developed cutting tool at the same level that was 8 mm deep and 200 mm wide. Also, the textures on the rake face of the developed tool were completely worn out. From this result, it was found
T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
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Fig. 1. Previously developed cutting tool with nano-/micro-textured surface [5].
Fig. 3. Profiles of rake face of cutting tool after cutting for 300 m (left: threedimensional profile; right: sectional profile). (a) Polished tool, (b) Tool with nano-/ micro-textured surface.
Fig. 2. Experimental setup of face-milling tests.
that the nano/micro-grooves, which significantly improve the anti-adhesive effect in the cutting of aluminum alloy, were not effective in improving the tool wear resistance in the cutting of steel material. 3. Newly developed cutting tools with micro-stripe grooved surfaces When compared to aluminum alloys, steel is difficult to cut because of high hardness, which leads to high cutting forces, and temperature, which leads to severe mechanical and thermal wear. Moreover, on the rake face of the previously developed tool, after cutting, wear tracks having micrometer-scale surface roughness were observed and are shown in Fig. 4. In the cutting process, it is known that hard wear debris that falls out of cutting tools and workpieces plows the tool surface, promoting the progression of wear [7,8]. As shown in Fig. 1, the nano/micro-grooves form submicrometer-scale sine waves and are thought to lead to extremely high contact stresses between the tool surface and the
Fig. 4. SEM image of rake face of cutting tool with nano-/micro-textured surface after cutting.
chip and negligibly small size and volume of grooves to retain enough fluid and trap the wear debris. Considering the above-mentioned results, we designed new textures of cutting tool surfaces to serve three purposes: (1) to reduce the actual contact stress between the tool surface and the chip; (2) to improve the cooling effect by retaining enough fluid; and (3) to trap wear particles that are several micrometers in diameter. To achieve these goals, periodic rectangular grooves that were several micrometers deep with a width and spacing of several tens of micrometers were then newly introduced onto the cutting tool surface. The grooves were produced by femtosecond laser technology (Canon Machinery Inc., Model Surfbeat R). A single laser irradiation generates a 0.2-mm-deep concave surface that is an envelope surface of peaks of nano/micro-grooves. Then, concave shapes with depths of the order of micrometers can be produced by multiple laser irradiation. 4. Cutting tool performance
Table 1 Cutting conditions. Workpiece Tool
Tool geometry
Cutting speed Depth of cut Feed rate Cutting fluid Supply rate
4.1. Influence of groove depth and direction Carbon steel S53C W 60 mm–L 66 mm Cemented carbide K10 Sumitomo Electric Hardmetal Corp., SEKN42MT Axial rake angle, uA Radial rake angle, uR True rake angle, a Corner angle, g Cutter diameter, D 200 m/min 2 mm 0.2 mm/rev. Emulsion type NEOS Co., Ltd., Finecut CFS-100 12.6 L/min
208 38 12.48 458 80 mm
Four types of cutting tools were prepared, as shown in Fig. 5, by applying the above mentioned laser technology: (1) a tool with 1-mm-deep grooves that are parallel to the edge; (2) a tool with 1-mm-deep grooves that are orthogonal to the edge; (3) a tool with 5-mm-deep grooves that are parallel to the edge; and (4) a tool with 5-mm-deep grooves that are orthogonal to the edge. The groove width and interval were set to 50 mm for all tools. The groove dimensions were set considering the wear size of the polished tool and the tool with nano-/micro-texutred surface. From Figs. 3 and 6(a) and (b), we found that 1-mm-deep grooves did not effectively improve wear resistance. More specifically, the grooves were completely worn out and severe crater wear
T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
573
Fig. 7. Profiles of rake face of developed tool with 5-mm deep and 20-mm wide and apart grooves parallel to edge after cutting for 300 m (left: three-dimensional profile; right: sectional profile).
chips flowing over the rake face of the tool enter into the grooves and lead to increased wear.
Fig. 5. Newly developed cutting tool with periodical stripe grooved surface.
occurred at the same depth of 8 mm, similar to that occurring in the polished tool. This is because the grooves were too shallow to retain enough cutting fluid and trap wear debris. As shown in Fig. 6(c), the maximum depth of the crater wear of a tool with 5-mm-deep grooves, which are parallel to the edge, was reduced from 8 mm (obtained in the polished tool) to 3 mm. On the other hand, the grooves that were orthogonal to the edge slightly suppressed the wear (Fig. 6(d)). The influence of the groove direction is the same as that of the nano/micro-texture direction [5]. In the case of the tool with grooves orthogonal to the edge,
4.2. Influence of groove width and spacing Fig. 7 shows the results of the developed tool with grooves that are parallel to the edge and are 5 mm deep, 20 mm wide, and 20 mm apart. Figs. 6(c) and 7 confirm that the maximum depth of the crater wear was almost the same (3 mm), regardless of the width and spacing of the grooves, and the grooves in the tool that were 20 mm wide and 20 mm apart were clearer than those in the tool with grooves that were 50 mm wide and 50 mm apart after cutting. The obtained chips are shown in Fig. 8. The curl diameter of the chips obtained in the developed tool with grooves 20 mm wide and 20 mm apart was smaller than or equal to those of the polished tool and the developed tool with grooves 50 mm wide and 50 mm apart. This result implies that the tool surface with grooves that are 20 mm wide and 20 mm apart has excellent lubricity between the tool surface and the chip [9]. This is thought to be because grooves having small width and intervals evenly supply retained fluid on the tool surface. We evaluated changes in the tool wear—the maximum depth of crater wear (KT)—for the developed tool with grooves that were parallel to the edge and were 5 mm deep, 20 mm wide, and 20 mm apart, and having high wear resistance and lubricity from the above mentioned findings (Fig. 9). As shown in this figure, the
Fig. 8. Chip shapes. (a) Polished tool (b) Tool with grooves 50 mm wide and 50 mm apart (c) Tool with grooves 20 mm wide and 20 mm apart.
Fig. 6. Profiles of rake face of developed cutting tool after cutting for 300 m (left: three-dimensional profile; right: sectional profile). (a) Developed tool with 1-mmdeep grooves parallel to edge. (b) Developed tool with 1-mm-deep grooves orthogonal to edge. (c) Developed tool with 5-mm-deep grooves parallel to edge. (d) Developed tool with 5-mm-deep grooves orthogonal to edge.
Fig. 9. Variation of maximum depth of crater wear (KT) with cutting length.
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T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
Fig. 12. Developed TiAlN-coated tool (left: three-dimensional profile; right: sectional profile). (a) After cutting for 300 m, (b) After cutting for 600 m. Fig. 10. TiAlN-coated polished tool (left: three-dimensional profile; right: sectional profile). (a) After cutting for 300 m, (b) After cutting for 600 m.
Fig. 13. Chip shapes. (a) TiAlN-coated polished tool, (b) Developed TiAlN-coated tool. Fig. 11. Rake face of polished tool after cutting, (a) SEM image, (b) EDX-W, Co image.
6. Conclusion
crater wear of the developed cutting tool progressed at the same rate as that of the polished tool after cutting for 300 m, and the grooves on the rake face diminished after cutting for 600 m. 5. TiAlN-coated cutting tools with micro-stripe grooved surfaces To improve wear resistance, a TiAlN film with 2.4 mm thickness, which is commonly employed to cut tools that are used to cut steel, which has high hardness and heat resistance, was coated by physical vapor deposition after creating the grooves. The coating did not change the groove depth. Fig. 10 shows the profiles of the rake face of the TiAlN-coated polished tool after cutting. As shown in this figure, chip adhesion and partial wear occurred and increased with cutting length. To determine the adhesion and wear on the tool surface in detail, we observed the rake face of the cutting tools after cutting for 600 m by SEM and energy-dispersive X-ray spectrometry (EDX) (Fig. 11). White spots in Fig. 11(b) indicate tungsten (W) and cobalt (Co) atom distribution. From this figure, it was found that the TiAlN coating film flaked and exposed the tool substrate (W–Co-cemented carbide), as indicated by the circle. The TiAlN-coated film is thought to flake when chip adhesion was shed at the secession of the cutting edge from the workpiece in intermittent cutting processes such as the milling process [10]. From Fig. 12, we found that the TiAlN coating and grooves with 5 mm depth, 20 mm width, and 20 mm interval parallel to the main cutting edge significantly decreased chip adhesion and tool wear, although some thermal cracks were observed. Fig. 13 shows that the curl diameter of the chips obtained in the developed tool was smaller than that of the polished tool. From this figure, it was confirmed that the developed TiAlN-coated tool surface had good lubricity.
To improve tool wear resistance in steel cutting, the the functionalization of tool surfaces according to texture was adopted. Experimental results showed that nano/micro-grooves on the tool surface, which were 100–150 nm deep and 700 nm apart, were not effective at improving the wear resistance, and micro-stripe grooves that were 5 mm deep, 20 mm wide, and 20 mm apart, and parallel to the main cutting edge and TiAlN coating significantly improved the wear resistance and lubricity of the cutting tool surface. Acknowledgements This work was partially supported by a Grant-in-Aid for Scientific Research (No. 21560123, 2011) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. References [1] Byrne G, Dornfeld D, Denkena B (2003) Advancing Cutting Technology. Annals of the CIRP 52/2:483–507. [2] Evans CJ, Bryan JB (1999) Structured, Textured or Engineered Surfaces. Annals of the CIRP 48/2:541–556. [3] Bruzzone AAG, Costa HL, Lonardo PM, Lucca DA (2008) Advances in Engineered Surfaces for Functional Performance. Annals of the CIRP 57/2:750–769. [4] Enomoto T, Watanabe T, Aoki Y, Ohtake N (2007) Development of a Cutting Tool with Micro Structured Surface. Japanese Transactions of the Japan Society of Mechanical Engineers Series C 73/729:288–293. [5] Enomoto T, Sugihara T (2010) Improving Anti-Adhesive Properties of Cutting Tool Surfaces by Nano-/Micro-Textures. Annals of the CIRP 59:597–600. [6] Kawahara K, Sawada H, Mori A (2008) Effect of Surface Periodic Structures for Bi-directional Rotation on Water Lubrication Properties of SiC. Tribology Online of the Japan Society of Tribologists 3/2:122–126. [7] Suh NP, Saka N (1987) Surface Engineering. Annals of the CIRP 36/1:403–408. [8] Suh NP, Sin HC (1981) The Genesis of Friction. Wear 69:91–144. [9] Fukui H, Okida J, Omori N, Moriguchi H, Tsuda K (2004) Cutting Performance of DLC Coated Tools in Dry Machining Aluminum Alloys. Surface & Coatings Technology 187:70–76. [10] Itakura K, Kuroda M, Omokawa H, Yamamoto K (1999) Wear Mechanism of Coated Cemented Carbide Tool in Cutting of Super Heat Resisting Alloy Inconel 718. Journal of the Japan Society for Precision Engineering 65/7:976–981.
Contents lists available at SciVerse ScienceDirect
CIRP Annals - Manufacturing Technology jou rnal homep age : ht t p: // ees .e lse vi er . com /ci r p/ def a ult . asp
Highly wear-resistant cutting tools with textured surfaces in steel cutting Toshiyuki Enomoto (2)*, Tatsuya Sugihara, Satoshi Yukinaga, Kenji Hirose, Urara Satake Department of Mechanical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords: Cutting tool Surface Texture
To increase cutting tool life, our previous studies have proposed cutting tools with nano-/micro-textured surfaces, which displayed high anti-adhesive effects in the cutting of aluminum alloys. In this study, the previously developed tools were used to cut steel materials with the goal of improving wear resistance. However, a serious problem regarding the wear still remained. Therefore, to overcome this problem, new TiAlN-coated cutting tools with periodical stripe-grooved surfaces were developed. Face-milling experiments on steel materials showed that the new texture and coating on the tool surface significantly reduce the tool wear. ß 2012 CIRP.
1. Introduction In cutting processes, the improvement of anti-adhesive properties and wear resistance of cutting tools are constantly and strongly required to increase the tool life. Therefore, many cutting tool technologies pertaining to material, geometry, surface coating, and surface finishing have been developed [1]. However, the technologies cannot meet recent requirements in practical processes, especially in steel cutting, because the high mechanical stress and heat generated on the tools’ surfaces result in significant tool wear. To improve cutting tool properties, we adopted a surface engineering approach [2,3], namely, a functionalization of tool surfaces by textures [4]. In our previous study [5], we developed diamond-like carbon-coated cutting tools with nano-/microtextured surfaces to determine the role of the faces of the textured tool rake on the retention of the cutting fluid and the decrease in the contact area between the tool surface and chip. Face-milling experiments on aluminum alloys showed that textured surfaces significantly improve the lubricity and anti-adhesive properties at the tool–chip interface. In this study, the previously [5] developed tools with nano-/ micro-textured surfaces were applied to the cutting of a carbon steel material (S53C) with the aim of improving tool wear resistance. Based on our findings, we developed a cutting tool with a periodical stripe-grooved surface to improve the desired wear resistance. In addition, we evaluated the corresponding cutting performance. 2. Nano-/micro-textured cutting tool surfaces 2.1. Cutting tools with nano-/micro-textured surfaces In a previous study [5], cutting tools with nano-/micro-textured surfaces were developed by laser-induced periodic surfacestructuring technology [6]. The irradiation of linearly polarized
* Corresponding author. 0007-8506/$ – see front matter ß 2012 CIRP. http://dx.doi.org/10.1016/j.cirp.2012.03.123
femtosecond laser pulses on a surface induces interference between the incident laser pulses and surface-scattered light or plasma waves on the surface. Precise and regular grooves are selforganized with the spacing of regular structures being either the same or smaller than the laser wavelength. Fig. 1 shows a schematic illustration, a scanning electron microscope (SEM) (JEOL Ltd., JSM-5800A) image, and atomic force microscope (AFM) (Pacific Nanotechnology Inc., Nano-R2) images of the cutting tool [5]. As shown in this figure, regular grooves that are 100–150 nm deep and 700 nm apart were generated on the tool rake face as sine waves. The grooves formed were orthogonal to the chip flow direction, i.e., parallel to the main cutting edge, to obtain good cutting properties [5]. Before laser irradiation, the tool rake face was polished with diamond slurry to obtain a surface roughness of 40 nm (peak to valley). 2.2. Cutting experiment procedures and cutting tool performance Cutting experiments involving both a cutting tool with a polished surface and the previously developed cutting tool were conducted on carbon steel S53C using a vertical machining center (Yamazaki Mazak Corp., AJV-18). The experimental setup is illustrated in Fig. 2. The center of the cutter was set on the center line of the workpiece. Table 1 lists the cutting conditions. A cemented carbide tool (Sumitomo Electric Hardmetal Corp., SEKN42MT) with a 100-mm-wide chamfer was used as the cutting tool insert. An emulsion-type cutting fluid (NEOS Co., Ltd., Finecut CFS-100) was supplied at a flow rate of 12.6 L/min. After cutting, rake faces of the cutting tools were measured using a two/three-dimensional stylus-type profile instrument (Kosaka Laboratory Ltd., SE3500K). Fig. 3 shows the threedimensional profiles and the sectional profiles of the rake faces of the polished tool and the previously developed cutting tool after cutting for 300 m. As shown in this figure, severe crater wear occurred on the rake faces of both the polished tool and developed cutting tool at the same level that was 8 mm deep and 200 mm wide. Also, the textures on the rake face of the developed tool were completely worn out. From this result, it was found
T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
572
Fig. 1. Previously developed cutting tool with nano-/micro-textured surface [5].
Fig. 3. Profiles of rake face of cutting tool after cutting for 300 m (left: threedimensional profile; right: sectional profile). (a) Polished tool, (b) Tool with nano-/ micro-textured surface.
Fig. 2. Experimental setup of face-milling tests.
that the nano/micro-grooves, which significantly improve the anti-adhesive effect in the cutting of aluminum alloy, were not effective in improving the tool wear resistance in the cutting of steel material. 3. Newly developed cutting tools with micro-stripe grooved surfaces When compared to aluminum alloys, steel is difficult to cut because of high hardness, which leads to high cutting forces, and temperature, which leads to severe mechanical and thermal wear. Moreover, on the rake face of the previously developed tool, after cutting, wear tracks having micrometer-scale surface roughness were observed and are shown in Fig. 4. In the cutting process, it is known that hard wear debris that falls out of cutting tools and workpieces plows the tool surface, promoting the progression of wear [7,8]. As shown in Fig. 1, the nano/micro-grooves form submicrometer-scale sine waves and are thought to lead to extremely high contact stresses between the tool surface and the
Fig. 4. SEM image of rake face of cutting tool with nano-/micro-textured surface after cutting.
chip and negligibly small size and volume of grooves to retain enough fluid and trap the wear debris. Considering the above-mentioned results, we designed new textures of cutting tool surfaces to serve three purposes: (1) to reduce the actual contact stress between the tool surface and the chip; (2) to improve the cooling effect by retaining enough fluid; and (3) to trap wear particles that are several micrometers in diameter. To achieve these goals, periodic rectangular grooves that were several micrometers deep with a width and spacing of several tens of micrometers were then newly introduced onto the cutting tool surface. The grooves were produced by femtosecond laser technology (Canon Machinery Inc., Model Surfbeat R). A single laser irradiation generates a 0.2-mm-deep concave surface that is an envelope surface of peaks of nano/micro-grooves. Then, concave shapes with depths of the order of micrometers can be produced by multiple laser irradiation. 4. Cutting tool performance
Table 1 Cutting conditions. Workpiece Tool
Tool geometry
Cutting speed Depth of cut Feed rate Cutting fluid Supply rate
4.1. Influence of groove depth and direction Carbon steel S53C W 60 mm–L 66 mm Cemented carbide K10 Sumitomo Electric Hardmetal Corp., SEKN42MT Axial rake angle, uA Radial rake angle, uR True rake angle, a Corner angle, g Cutter diameter, D 200 m/min 2 mm 0.2 mm/rev. Emulsion type NEOS Co., Ltd., Finecut CFS-100 12.6 L/min
208 38 12.48 458 80 mm
Four types of cutting tools were prepared, as shown in Fig. 5, by applying the above mentioned laser technology: (1) a tool with 1-mm-deep grooves that are parallel to the edge; (2) a tool with 1-mm-deep grooves that are orthogonal to the edge; (3) a tool with 5-mm-deep grooves that are parallel to the edge; and (4) a tool with 5-mm-deep grooves that are orthogonal to the edge. The groove width and interval were set to 50 mm for all tools. The groove dimensions were set considering the wear size of the polished tool and the tool with nano-/micro-texutred surface. From Figs. 3 and 6(a) and (b), we found that 1-mm-deep grooves did not effectively improve wear resistance. More specifically, the grooves were completely worn out and severe crater wear
T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
573
Fig. 7. Profiles of rake face of developed tool with 5-mm deep and 20-mm wide and apart grooves parallel to edge after cutting for 300 m (left: three-dimensional profile; right: sectional profile).
chips flowing over the rake face of the tool enter into the grooves and lead to increased wear.
Fig. 5. Newly developed cutting tool with periodical stripe grooved surface.
occurred at the same depth of 8 mm, similar to that occurring in the polished tool. This is because the grooves were too shallow to retain enough cutting fluid and trap wear debris. As shown in Fig. 6(c), the maximum depth of the crater wear of a tool with 5-mm-deep grooves, which are parallel to the edge, was reduced from 8 mm (obtained in the polished tool) to 3 mm. On the other hand, the grooves that were orthogonal to the edge slightly suppressed the wear (Fig. 6(d)). The influence of the groove direction is the same as that of the nano/micro-texture direction [5]. In the case of the tool with grooves orthogonal to the edge,
4.2. Influence of groove width and spacing Fig. 7 shows the results of the developed tool with grooves that are parallel to the edge and are 5 mm deep, 20 mm wide, and 20 mm apart. Figs. 6(c) and 7 confirm that the maximum depth of the crater wear was almost the same (3 mm), regardless of the width and spacing of the grooves, and the grooves in the tool that were 20 mm wide and 20 mm apart were clearer than those in the tool with grooves that were 50 mm wide and 50 mm apart after cutting. The obtained chips are shown in Fig. 8. The curl diameter of the chips obtained in the developed tool with grooves 20 mm wide and 20 mm apart was smaller than or equal to those of the polished tool and the developed tool with grooves 50 mm wide and 50 mm apart. This result implies that the tool surface with grooves that are 20 mm wide and 20 mm apart has excellent lubricity between the tool surface and the chip [9]. This is thought to be because grooves having small width and intervals evenly supply retained fluid on the tool surface. We evaluated changes in the tool wear—the maximum depth of crater wear (KT)—for the developed tool with grooves that were parallel to the edge and were 5 mm deep, 20 mm wide, and 20 mm apart, and having high wear resistance and lubricity from the above mentioned findings (Fig. 9). As shown in this figure, the
Fig. 8. Chip shapes. (a) Polished tool (b) Tool with grooves 50 mm wide and 50 mm apart (c) Tool with grooves 20 mm wide and 20 mm apart.
Fig. 6. Profiles of rake face of developed cutting tool after cutting for 300 m (left: three-dimensional profile; right: sectional profile). (a) Developed tool with 1-mmdeep grooves parallel to edge. (b) Developed tool with 1-mm-deep grooves orthogonal to edge. (c) Developed tool with 5-mm-deep grooves parallel to edge. (d) Developed tool with 5-mm-deep grooves orthogonal to edge.
Fig. 9. Variation of maximum depth of crater wear (KT) with cutting length.
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T. Enomoto et al. / CIRP Annals - Manufacturing Technology 61 (2012) 571–574
Fig. 12. Developed TiAlN-coated tool (left: three-dimensional profile; right: sectional profile). (a) After cutting for 300 m, (b) After cutting for 600 m. Fig. 10. TiAlN-coated polished tool (left: three-dimensional profile; right: sectional profile). (a) After cutting for 300 m, (b) After cutting for 600 m.
Fig. 13. Chip shapes. (a) TiAlN-coated polished tool, (b) Developed TiAlN-coated tool. Fig. 11. Rake face of polished tool after cutting, (a) SEM image, (b) EDX-W, Co image.
6. Conclusion
crater wear of the developed cutting tool progressed at the same rate as that of the polished tool after cutting for 300 m, and the grooves on the rake face diminished after cutting for 600 m. 5. TiAlN-coated cutting tools with micro-stripe grooved surfaces To improve wear resistance, a TiAlN film with 2.4 mm thickness, which is commonly employed to cut tools that are used to cut steel, which has high hardness and heat resistance, was coated by physical vapor deposition after creating the grooves. The coating did not change the groove depth. Fig. 10 shows the profiles of the rake face of the TiAlN-coated polished tool after cutting. As shown in this figure, chip adhesion and partial wear occurred and increased with cutting length. To determine the adhesion and wear on the tool surface in detail, we observed the rake face of the cutting tools after cutting for 600 m by SEM and energy-dispersive X-ray spectrometry (EDX) (Fig. 11). White spots in Fig. 11(b) indicate tungsten (W) and cobalt (Co) atom distribution. From this figure, it was found that the TiAlN coating film flaked and exposed the tool substrate (W–Co-cemented carbide), as indicated by the circle. The TiAlN-coated film is thought to flake when chip adhesion was shed at the secession of the cutting edge from the workpiece in intermittent cutting processes such as the milling process [10]. From Fig. 12, we found that the TiAlN coating and grooves with 5 mm depth, 20 mm width, and 20 mm interval parallel to the main cutting edge significantly decreased chip adhesion and tool wear, although some thermal cracks were observed. Fig. 13 shows that the curl diameter of the chips obtained in the developed tool was smaller than that of the polished tool. From this figure, it was confirmed that the developed TiAlN-coated tool surface had good lubricity.
To improve tool wear resistance in steel cutting, the the functionalization of tool surfaces according to texture was adopted. Experimental results showed that nano/micro-grooves on the tool surface, which were 100–150 nm deep and 700 nm apart, were not effective at improving the wear resistance, and micro-stripe grooves that were 5 mm deep, 20 mm wide, and 20 mm apart, and parallel to the main cutting edge and TiAlN coating significantly improved the wear resistance and lubricity of the cutting tool surface. Acknowledgements This work was partially supported by a Grant-in-Aid for Scientific Research (No. 21560123, 2011) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. References [1] Byrne G, Dornfeld D, Denkena B (2003) Advancing Cutting Technology. Annals of the CIRP 52/2:483–507. [2] Evans CJ, Bryan JB (1999) Structured, Textured or Engineered Surfaces. Annals of the CIRP 48/2:541–556. [3] Bruzzone AAG, Costa HL, Lonardo PM, Lucca DA (2008) Advances in Engineered Surfaces for Functional Performance. Annals of the CIRP 57/2:750–769. [4] Enomoto T, Watanabe T, Aoki Y, Ohtake N (2007) Development of a Cutting Tool with Micro Structured Surface. Japanese Transactions of the Japan Society of Mechanical Engineers Series C 73/729:288–293. [5] Enomoto T, Sugihara T (2010) Improving Anti-Adhesive Properties of Cutting Tool Surfaces by Nano-/Micro-Textures. Annals of the CIRP 59:597–600. [6] Kawahara K, Sawada H, Mori A (2008) Effect of Surface Periodic Structures for Bi-directional Rotation on Water Lubrication Properties of SiC. Tribology Online of the Japan Society of Tribologists 3/2:122–126. [7] Suh NP, Saka N (1987) Surface Engineering. Annals of the CIRP 36/1:403–408. [8] Suh NP, Sin HC (1981) The Genesis of Friction. Wear 69:91–144. [9] Fukui H, Okida J, Omori N, Moriguchi H, Tsuda K (2004) Cutting Performance of DLC Coated Tools in Dry Machining Aluminum Alloys. Surface & Coatings Technology 187:70–76. [10] Itakura K, Kuroda M, Omokawa H, Yamamoto K (1999) Wear Mechanism of Coated Cemented Carbide Tool in Cutting of Super Heat Resisting Alloy Inconel 718. Journal of the Japan Society for Precision Engineering 65/7:976–981.