Coated cutting tool and method for manufacturing the same
09849516 · 2017-12-26
Assignee
Inventors
Cpc classification
B23B27/148
PERFORMING OPERATIONS; TRANSPORTING
B23K26/082
PERFORMING OPERATIONS; TRANSPORTING
B23K26/361
PERFORMING OPERATIONS; TRANSPORTING
C23C28/044
CHEMISTRY; METALLURGY
C23C28/042
CHEMISTRY; METALLURGY
B23K26/40
PERFORMING OPERATIONS; TRANSPORTING
Y10T407/24
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
B23B27/00
PERFORMING OPERATIONS; TRANSPORTING
B23K26/361
PERFORMING OPERATIONS; TRANSPORTING
B23B27/14
PERFORMING OPERATIONS; TRANSPORTING
C23C30/00
CHEMISTRY; METALLURGY
B23K26/40
PERFORMING OPERATIONS; TRANSPORTING
B23K26/082
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A coated cutting tool includes a substrate with a rake side, a clearance side and a cutting edge, and a coating including a first layer and a second layer. The second layer includes an inner layer and an outer layer, wherein the first layer is exposed through an opening in the inner layer and the opening extends over at least a portion of the width of the cutting edge. Thereby, a double layer is provided in critical areas, whereas a single layer is provided in other areas. Preferably, the double oxide layer includes aluminum oxide layers. A method for manufacturing the coated cutting tool is also provided.
Claims
1. A coated cutting tool comprising: a substrate with a rake side, a clearance side and a cutting edge with an edge rounding described by an inscribed ellipse with a first axis along the rake side of W and a second axis along the clearance side of H at the intersection of the rake side and the clearance side; and a coating with a thickness T comprising a first layer and a second layer deposited on the first layer, wherein the second layer comprises a sandwich structure of an inner layer and an outer layer, wherein the inner layer has an opening to the first layer that extends over at least a portion of the width of the cutting edge and along at least a portion of the cutting edge in the orthogonal direction and the outer layer covers at least the opening and a portion of the inner layer.
2. The coated cutting tool of claim 1, wherein the opening extends over at least the whole width of the cutting edge.
3. The coated cutting tool of claim 1, wherein the opening extends into the clearance side.
4. The coated cutting tool of claim 1, wherein the opening extends at least H+T+2 mm into the clearance side from the rake side.
5. The coated cutting tool of claim 1, wherein the opening extends into the rake side.
6. The coated cutting tool of claim 1, wherein the opening extends partly into a primary land of the rake side.
7. The coated cutting tool of claim 1, wherein the opening extends at least 50 μm into the rake side.
8. The coated cutting tool of claim 1, wherein the opening extends at least 100 μm into the rake side.
9. The coated cutting tool of claim 1, wherein the first layer has a higher absorption coefficient for light than the inner layer.
10. The coated cutting tool of claim 1, wherein the inner layer is an inner aluminum oxide layer and the outer layer is an outer aluminum oxide layer.
11. The coated cutting tool of claim 10, wherein said aluminum oxide layers are made of α-Al2O3.
12. The coated cutting tool of claim 10, wherein the thickness of the aluminum oxide layers is 2-10 μm.
13. The coated cutting tool of claim 1, wherein the thickness of the inner layers is 1-10 μm and the outer layer is 2-20 μm.
14. The coated cutting tool of claim 1, wherein the first layer consists of one or more layers selected from titanium carbide, titanium nitride, titanium carbonitride, titanium oxycarbide and titanium oxycarbonitride, and has a thickness of 2-15 μm.
15. A method of manufacturing a substrate with a rake side, a clearance side and a cutting edge at the intersection of the rake side and the clearance side, and a coating comprising an first layer and an second layer deposited on the first layer, wherein the method comprises the steps of: depositing the first layer on a surface area extending over each of the rake side, the clearance side and the cutting edge; depositing an inner layer on the surface area covered by the first layer; selectively removing the inner layer by lift-off, wherein the inner layer is exposed to laser light arranged to irradiate the first layer through the inner layer and being absorbed by the first layer, thereby exposing the first layer through an opening in the inner layer, wherein said opening extends over at least a portion of the width of the cutting edge and along at least a portion of the cutting edge in the orthogonal direction; and depositing an outer layer that covers at least the opening and a portion of the inner layer.
16. The method of claim 15, further comprising the step of depositing an intermediate layer prior to depositing the outer layer.
17. The coated cutting tool of claim 13, wherein the thickness of the inner layer is 2-5 μm.
18. The coated cutting tool of claim 13, wherein the thickness of the outer layer is 4-10 μm.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) Embodiments of the invention will now be described with reference to the accompanying drawings, wherein:
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DETAILED DESCRIPTION
Example 1
(10) Coated cutting tools were manufactured. First, cemented carbide CNMG120408-PM substrates with a composition of 7.5 wt-% Co and balance WC, a Hc value of 13 kA/m (using a Foerster Koerzimat CS1.096 according to DIN IEC 60404-7) and a hardness of HV3=15 GPa were manufactured by pressing powder and sintering the pressed bodies. Prior to coating deposition the substrates were edge rounded to about 50 μm by wet blasting.
(11) Referring to
(12) After deposition the coated cutting tools were subjected to a laser operation and a subsequent wet blasting operation. The laser was a diode-pumped YAG laser (Violine) operated at 13 W, 1064 nm, a pulse length of 6 ns (measured at 10 kHz) and a repetition frequency of 20 kHz. A focal lens with 254 mm focal length was used resulting in a spot size of 100 μm. The laser beam was directed in an orthogonal direction to the clearance side at the nose of the cutting tool and an area of 6×2 mm was irradiated in a raster scan with scan lines having a width of 0.1 mm in parallel and orthogonally to the cutting edge, as schematically illustrated in
(13) The wet blasting included both top blasting and side blasting, i.e. with the blasting media bombarding the coated cutting tool to the rake side and the clearance side, respectively, using 220 mesh Al.sub.2O.sub.3 particles at a pressure of 1.4-3 bar.
(14) The wet blasting removed the intermediate layer in a surface area extending from the edge into the clearance side, see
Example 2
(15) Coated cutting tools were manufactured in accordance with Example 1 except for a different wet blasting operation, where only top blasting was applied, see
Example 3
(16) Cutting tools according to prior art comprising CNMG120408-PM substrates with a composition of 7.5 wt-% Co and balance WC, a Hc value of 13 kA/m (using a Foerster Koerzimat CS1.096 according to DIN IEC 60404-7) and a hardness of HV3=15 GPa and a coating with a 9 μm first layer of Ti(C,N) and a 4.5 μm second layer of α-Al.sub.2O.sub.3 and a Ti(C,N) color layer were manufactured as in Example 2, but without the laser operation. The top blasting operation removed the color layer on the rake side.
Example 4
(17) Cutting tools were manufactured as in Example 2 without removing the second aluminum oxide layer.
Example 5
(18) Cutting tool inserts from Examples 2-4 were tested with respect to flank wear and crater wear by turning in ball bearing steel (Ovako 825B, Tibnor) with depth of cut 2 mm, cutting speed 240 m/min, feed 0.3 mm/rev and using coolant. Tool life criterion for flank wear was for crater wear exceeding 0.2 mm.sup.2 and flank wear exceeding v.sub.B=0.4 mm, as measured by a light optical microscopy on the rake side and the clearance side, respectively. The tool life is presented in Table 1.
(19) TABLE-US-00001 TABLE 1 Tool life (minutes) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Crater wear n.a. >30 15 >30 Flank wear n.a. >30 18 >30
Example 6
(20) Coated cutting tools of Examples 1-4 were tested in facing of nodular cast iron SS0717 including intermittent cutting operations with coolant under the following conditions.
(21) Cutting speed, V.sub.c 170 m/min
(22) Feed, f.sub.n 0.1 mm/rev
(23) Depth of cut, a.sub.p 2 mm
(24) Flaking resistance was evaluated based on the percentage of flaking on the edge was observed after machining. The coated cutting tools of Ex. 1 and 4 did not show any flaking at all, whereas the cutting tool of Example 3 for individual inserts showed either no flaking at all or a flaking from 19 up to 45%. The coated cutting tool of Example 2 showed a flaking degree of from 47 up to 85%.
Example 7
(25) Coated cutting tools were manufactured as follows. First, cemented carbide CNMG120408-PM substrates with a composition of 4.1 wt-% Co and balance WC, a Hc value of 16 kA/m (using a Foerster Koerzimat CS1.096 according to DIN IEC 60404-7) and a hardness of HV3=16 GPa were manufactured by pressing powder and sintering the pressed bodies. Prior to coating deposition the substrates were edge rounded to about 45 μm, as measured as a circle radius (H≈W≈45 μm), by brushing, and subsequently blasted with alumina grits in water at low pressure in order to remove any plastic residue from the brushing process. The blasting pressure was 1.8 bar and the alumina grits were F150 mesh (FEPA 42-1:2006).
(26) Said substrates were coated in three different CVD processes and they are all described in the following.
(27) Coating 1, consisting of a first layer and a second layer, was deposited by CVD on the substrates. The first layer is a Ti(C,N,O) layer with a total thickness of 11.3 μm, which consists of the layer sequence 0.4 μm TiN, 10.1 μm MTCVD Ti(C,N), 0.2 μm HTCVD Ti(C,N) and 0.6 μm Ti(C,O). The second layer is a 11.0 μm α-Al.sub.2O.sub.3 layer.
(28) Coating 2, shown schemetically in
(29) Coating 3, consisting of a first layer and a second layer, was deposited by CVD on the substrates. The first layer is a Ti(C,N,O) layer with a total thickness of 11.7 μm, which consists of the layer sequence 0.4 μm TiN, 10.5 μm MTCVD Ti(C,N), 0.2 μm HTCVD Ti(C,N) and 0.6 μm Ti(C,O). The second layer is a 3.0 μm α-Al.sub.2O.sub.3 layer.
(30) These three coating variants 1, 2 and 3 were deposited in a CVD reactor having radial gas flow using deposition conditions for growth of the MTCVD Ti(C,N) layers and the α-Al.sub.2O.sub.3 layer. A nucleation step was performed prior to growth of the MTCVD Ti(C,N) layer. Oxidation and nucleation steps were performed prior to growth of the α-alumina layer.
(31) After the CVD deposition the coated cutting tools were subjected to posttreatments, where 1b and 2b were subjected to a laser operation on the clearance side, coated cutting tools 2c, 2d where subjected to a first laser treatment on the clearance side and a second laser treatment with a shadow mask present on the rake side, while tools 1a, 2a, 3a were not laser treated.
(32) The laser used was a diode-pumped YAG laser (Violine 3 from Laservall) operated at 10 W, 1064 nm, a pulse length of 6 ns (measured at 10 kHz) and a repetition frequency of 20 kHz. A focal lens with 254 mm focal length was used resulting in a spot size of 100 μm. The laser beam was directed in an orthogonal direction to the clearance side at the nose of the cutting tool and an area of 6×2 mm was irradiated in a raster scan with scan lines having a width of 0.1 mm in parallel and orthogonally to the cutting edge, as schematically illustrated with arrow in
(33) The laser lift-off treatment on the clearance side remove the outer α-Al.sub.2O.sub.3 layer on the whole width of the edge of the coated cutting tools, and into the rake side, to a distance δ of about 50 μm of tool 1b and about 60 μm for tool 2b.
(34) As a mean to control the extent of removal of the outer α-Al.sub.2O.sub.3 layer on the rake side on tools 2c and 2d a cemented carbide shadow mask was used to define the extension of such a removal in a controlled way. The shadow mask protects the layers beneath the mask from being exposed of the laser and thereby the outer α-Al.sub.2O.sub.3 layer is not being removed from the area beneath the shadow mask. Different shadow masks were used in order to enable different distances δ of the outer α-Al.sub.2O.sub.3 layer being removed from edge and into the rake side in the laser process on the rake side. The distance δ is measured as the distance from the exposed cutting edge as seen from the rake side as disclosed above, and to the edge of the remaining outer α-Al.sub.2O.sub.3 layer.
(35) The laser treatment were for all the examples extended in the direction of the cutting edge to a position outside the cutting depth.
(36) Four different exposed distances δ from the edge into the rake side were thus manufactured, about 50 μm, about 60 μm, about 130 μm and about 200 μm. Tools provided with coating 1 was subjected to a laser operation removing the outer α-Al.sub.2O.sub.3 layer on the rake side from the edge to a distances δ of about 50 μm. Tools provided with coating 2 were subjected to a laser operation removing the outer α-Al.sub.2O.sub.3 layer on the rake side from the edge to a distances δ of about 60 μm, about 130 μm and about 200 μm respectively. The resulting average distance δ for the laser treated tool 1b, 2b, 2c and 2d is shown in Table 2.
(37) TABLE-US-00002 TABLE 2 Tool 1b 2b 2c 2d Average 50 60 130 200 distance δ (μm)
(38) Finally a wet blasting was performed on the rake sides of all the cutting tools, here called a final top blasting. The aim of this treatment was to introduce compressive stresses into the outermost coatings and thereby increase the edge toughness of the tools. The aim was further to smoothen the edge of the remaining outer α-Al.sub.2O.sub.3 layer and to remove the intermediate layer in the exposed surface area. The blaster slurry consisted of 20 vol-% alumina grits in water and an angle of 90° between the rake side of the cutting insert and the direction of the blaster slurry. The distance between the gun nozzle and the surface of the insert was about 145 mm. The pressure of the slurry to the gun was 1.8 bar for all samples, while the pressure of air to the gun was 2.1 bar for all tools. The alumina grits were F220 mesh (FEPA 42-1:2006). The time for blasting per area unit was about 4 seconds. A summary of the coated cutting tools 1a, 1b, 2a, 2b, 2c, 2d, and 3a manufactured in Example 7 is presented in Table 3.
(39) A cross sectional image of the coated cutting tool 1b is shown in
(40) TABLE-US-00003 TABLE 3 First Inner Outer Laser layer α-Al.sub.2O.sub.3 α-Al.sub.2O.sub.3 treatment Laser treatment TiCN layer layer, Clearance Rake side with Final Tool (μm) (μm) (μm) side shadow mask topblasting 1a 11.3 — 11.0 No No Yes 1b 11.3 — 11.0 Yes No, δ = 50 μm Yes 2a 11.0 2.9 6.7 No No Yes 2b 11.0 2.9 6.7 Yes No, δ = 60 μm Yes 2c 11.0 2.9 6.7 Yes Yes, δ = 130 μm Yes 2d 11.0 2.9 6.7 Yes Yes, δ = 200 μm Yes 3a 11.7 — 3.0 No No Yes
Example 8—Toughness Test
(41) The coated cutting tools 1a, 2a, 2b, 2c, 2d, 3a of Example 7 were tested in a toughness test.
(42) The work piece material consist of two carbon steel bars (Fe 360BFN), mounted parallel to each other with a distance between them. In longitudinal turning of this work piece the cutting tool will be exposed to two interruptions per revolution. In this test the toughness of the cutting tool has shown to be critical for its lifetime. The following cutting data was used;
(43) Cutting speed v.sub.c: 130 m/min
(44) Depth of cut a.sub.p: 1.5 mm
(45) Water miscible metal working fluid was used.
(46) The cutting feed was increased continuously during the test. The start value was 0.15 mm/revolution. After 1 minute of cutting the feed value was 0.20 mm/revolution and after 2 minutes of cutting, the feed value was 0.25 mm/revolution, and after 3 minutes of cutting the feed value was 0.30 mm/revolution.
(47) An equipment for measuring the cutting forces was used. When an insert breakage occurred the cutting force increased clearly and the machine was stopped. 25 cutting edges were evaluated per cutting tool variant. The actual value of the cutting feed at fracture for each one of the 25 cutting edges was registered. The values were sorted from the lowest fracture feed value to the highest, for each cutting tool variant. The wear performance is shown in Table 4, presenting the feed at fracture for edge number 6, the median value of all 25 edges and the value for edge number 20.
(48) TABLE-US-00004 TABLE 4 Coated cutting tool 1a 2a 2b 2c 2d 3a Feed at fracture Rank 6 0.21 0.19 0.21 0.21 0.23 0.28 (mm/revolution) Median 0.23 0.21 0.23 0.22 0.24 0.29 Rank 20 0.25 0.22 0.25 0.24 0.25 0.30
(49) As can be seen in the Table 4 the tool 3a, comprising the relatively thin outer α-Al.sub.2O.sub.3 layer shows the best performance in this test and the tool 2a comprising a relatively thick outer α-Al.sub.2O.sub.3 layer shows a shorter time to fracture. The laser treated tool 2d shows a edge toughness performance in between the performance of tool 3a and tool 2a. Thus, the edge line toughness is slightly better for the laser treated tool 2d as compared to the tool 2a with a relatively thick outer α-Al.sub.2O.sub.3 layer on the edge. Tool 2d performs slightly better than the tools 2b and 1a in this test.
Example 9—Crater Wear Test
(50) The coated cutting tools according to table 1 in Example 7, i.e. tools 1a, 1b, 2a, 2b, 2c, 2d, 3a were tested in longitudinal turning in ball bearing steel (100CrMo7-3) using the following cutting data;
(51) Cutting speed v.sub.c 240 m/min
(52) Cutting feed, f: 0.3 mm/revolution
(53) Depth of cut, a.sub.p: 2 mm
(54) Insert style: CNMG120408-PM
(55) Water miscible metal working fluid was used.
(56) One cutting edge per cutting tool was evaluated.
(57) In analyzing the crater wear, the area of removed material on the rake side (crater wear) was measured, using a light optical microscope. The wear of each cutting tool was evaluated after 2 minutes cutting in the light optical microscope. The cutting process was then continued with a measurement after each 2 minutes run. Beside crater wear, flank wear and build up edge was also observed. The results are shown in Table 5.
(58) TABLE-US-00005 TABLE 5 Coated cutting Crater area after Crater area after Crater area after tool 14 min (mm.sup.2) 20 min (mm.sup.2) 24 min (mm.sup.2) 1a, 2a, 2b, 2c, 0 0 0 2d 1b 0 * * 3a 0.02 0.26 0.43 * The tool 1b with no α-Al.sub.2O.sub.3 in the edgeline reached its life time due to excessive flank wear after 16 minutes.
(59) As can be seen in Table 5, it was only the cutting tool 3a that showed crater wear. The cutting tool 1b reached its lifetime due to excessive flank wear after 16 minutes cutting. Cutting tool 1b is the only cutting tool in this test that did not comprise an alumina layer as the outermost layer at the cutting edge and clearance side. All the cutting tools with a relatively thick aluminum oxide at the crater area on the rake side showed good resistance against crater wear in this test.
(60) The crater wear area in this test started at a distance of about 300 μm from the exposed cutting edge, measured by light optical microscope as the shortest distance in the plane of the rake side.
Example 10—Flank and Crater Wear Test
(61) The coated cutting tools according to Table 1 in Example 7, i.e. tools 1a, 1b, 2a, 2b, 2c, 2d, 3a were tested in longitudinal turning in ball bearing steel (100CrMo7-3) using the following cutting data;
(62) Cutting speed v.sub.c 255 m/min
(63) Cutting feed, f: 0.3 mm/revolution
(64) Depth of cut, a.sub.p: 2 mm
(65) Insert style: CNMG120408-PM
(66) Water miscible metal working fluid was used.
(67) One cutting edge per cutting tool was evaluated.
(68) In analyzing the flank wear, the distance from the edge line to the bottom of the flank wear pattern, as seen perpendicular to the clearance side, was measured using a light optical microscope. In analyzing the crater wear, the area of removed material on the rake side (crater wear) was measured, using a light optical microscope. The wear of each cutting tool was evaluated after 4 minutes cutting in the light optical microscope. The cutting process was then continued with a measurement after each 4 minutes run. Beside crater wear, flank wear and build up edge were also observed. The results are shown in Table 6.
(69) TABLE-US-00006 TABLE 6 Coated Flank wear at main Flank wear at Time until flank wear cutting cutting edge secondary cutting reached or exceeded tool (mm) edge (mm) 0.4 mm (min) 1a 0.43 0.36 34 1b 0.40 0.30 12 2a 0.41 0.34 36 2b 0.43 0.48 24 2c 0.43 0.41 28 2d 0.41 0.32 28 3a 0.33* 0.28* 20* *The cutting tool 3a with a relatively thin α-Al.sub.2O.sub.3 at the whole insert reached life time due to crater wear.
(70) As can be seen in Table 6, the cutting tools 1a and 2a, i.e. the tools with the relatively thickest aluminium oxide over the edge, showed the highest resistance to flank wear. The cutting tools 1b, with no aluminum oxide over the edge, showed the lowest resistance to flank wear. The cutting tools 2b, 2c, 2d showed a higher flank wear resistance as compared to cutting tools 1b. The cutting tool 3a, with a relatively thin aluminum oxide layer covering the whole tool, showed crater wear in this test and the test was stopped before the flank wear criteria 0.4 mm was reached. The cutting tool 2d showed a higher wear resistance compared to 2b.
(71) Also in this test, the crater wear area started at a distance of about 300 μm from the exposed cutting edge, measured as the shortest distance in the plane of the rake side.
Example 11—Flank and Crater Wear Test
(72) The coated cutting tools according to table 1 in Example 7, i.e. samples 1a, 1b, 2a, 2b, 2c, 2d, 3a were tested in longitudinal turning in ball bearing steel (100CrMo7-3) using the following cutting data;
(73) Cutting speed v.sub.c 270 m/min
(74) Cutting feed, f: 0.3 mm/revolution
(75) Depth of cut, a.sub.p: 2 mm
(76) Insert style: CNMG120408-PM
(77) Water miscible metal working fluid was used.
(78) One cutting edge per cutting tool was evaluated.
(79) In analyzing the flank wear, the distance from the edge line to the bottom of the flank wear pattern, as seen perpendicular to the clearance side, was measured using a light optical microscope. In analyzing the crater wear, the area of removed material on the rake side (crater wear) was measured, using a light optical microscope. The wear of each cutting tool was evaluated after 4 minutes cutting in the light optical microscope. The cutting process was then continued with a measurement after each 4 minutes run. Beside crater wear, flank wear and build up edge was also observed. The results after 22 minutes are shown in Table 7.
(80) TABLE-US-00007 TABLE 7 Coated cutting Flank wear at Flank wear at tool after main cutting secondary cutting Crater wear 22 minutes. edge (mm) edge (mm) (mm.sup.2) 2b 0.34 0.40 0.06 2c 0.32 0.29 0.00 2d 0.30 0.28 0.00 * The cutting tool 3a with thin α-Al.sub.2O.sub.3 at the whole insert reached its life time due to crater wear.
(81) As shown in Table 7, the flank wear resistance is slightly higher for the cutting tool 2d as compared to the cutting tools 2b and 2c. The reason for this might be that a laser lift off close to the edge effects the shape and micro geometry of the cutting edge.
(82) The crater wear area in this test started at a distance of about 300 μm from the exposed cutting edge, measured as the shortest distance in the plane of the rake side.
Example 12
(83) Coated cutting tools in accordance with one embodiment of the invention were manufactured. First, cemented carbide CNMG120408-PM substrates with a composition of 7.5 wt-% Co and balance WC, a Hc value of 13 kA/m (using a Foerster Koerzimat CS1.096 according to DIN IEC 60404-7) and a hardness of HV3=15 GPa were manufactured by pressing powder and sintering the pressed bodies. Prior to coating deposition the substrates were edge rounded to about 45 μm (H≈W≈45 μm), as measured as a circle radius, by brushing, and subsequently blasted with alumina in water at low pressure in order to remove any plastic residue from the brushing process. The blasting pressure was 1.8 bar and the alumina grits were F150 mesh (FEPA 42-1:2006).
(84) So called reference coating variants were deposited by CVD on the substrates. A first layer was deposited consisting of a Ti(C,N,O) layer with a total thickness of 10.8 μm, which comprises the layer sequence 0.4 μm TiN, 9.6 μm MTCVD Ti(C,N), 0.2 μm HTCVD Ti(C,N) and 0.6 μm Ti(C,O). Subsequent to the first layer a 5.2 μm α-Al.sub.2O.sub.3 layer was deposited, hereinafter referred to as an inner layer.
(85) Some of the reference coating variants are then subjected to a subsequent wet blasting operation forming reference cutting tools.
(86) The laser lift off coating variants are obtained by using said reference coating variants and subsequent to the CVD deposition of the reference coating (comprising the first and inner layers) as disclosed above, such coated cutting tools were subjected to a laser lift off operation and finally a CVD deposition of an outer α-Al.sub.2O.sub.3 layer.
(87) The laser was a diode-pumped YAG laser (Violine 3 from Laservall) operated at 10 W, 1064 nm, a pulse length of 6 ns (measured at 10 kHz) and a repetition frequency of 20 kHz. A focal lens with 254 mm focal length was used resulting in a spot size of 100 μm. The laser beam was directed in an orthogonal direction to the clearance side and an area of 6×2 mm was irradiated in a raster scan with scan lines having a width of 0.1 mm in parallel and orthogonally to the cutting edge. The beam was displaced with a speed of 750 mm/s and three passes were made.
(88) The laser operation removed the inner α-Al.sub.2O.sub.3 layer and exposed the outer part of the first layer in an opening extending from the clearance side over the cutting edge an into the rake side.
(89) As a mean to control the removal of the inner α-Al.sub.2O.sub.3 layer on the rake face a cemented carbide shadow mask was used to define such a removal in a controlled way. Different shadow masks were used in order to enable variants with different distances (denoted as δ) of the rake face being removed in the laser process.
(90) The resulting δ for the laser lift off treated cutting tools was 50 μm, 130 μm and 200 μm, respectively. A cross-sectional image of the coated cutting tool with a δ of 50 μm is shown in
(91) Subsequent to laser processing these coated cutting tools are subjected to a wet blasting operation in order to remove residual surface layers, in a surface area extending from the edge into the clearance side, as a result of laser processing and in order to achieve optimal adhesion of outer CVD α-Al.sub.2O.sub.3 layer layer.
(92) An intermediate layer and an outer α-Al.sub.2O.sub.3 layer was deposited by CVD. The intermediate layer is a Ti(C,N,O) layer with a total thickness of 0.8 μm, which consists of the layer sequence 0.2 μm HTCVD Ti(C,N) and 0.6 μm Ti(C,O). The outer α-Al.sub.2O.sub.3 layer is a 4.8 μm α-Al.sub.2O.sub.3 layer. The laser liftoff coating variants are then subjected to a subsequent wet blasting operation.
(93) All of the blasting operations were performed on the rake faces of the cutting tools. The blaster slurry consisted of 20 vol-% alumina in water and an angle of 90° between the rake face of the cutting insert and the direction of the blaster slurry. The distance between the gun nozzle and the surface of the insert was about 145 mm. The pressure of the slurry to the gun was 1.8 bar for all samples, while the pressure of air to the gun was 2.1 bar for all samples. The alumina grits were F220 mesh (FEPA 42-1:2006). The time for blasting per area unit was about 4 seconds.
(94) All of the coatings were deposited in a CVD reactor having radial gas flow using deposition conditions for growth of the MTCVD Ti(C,N) layers and the α-Al.sub.2O.sub.3 layer. A nucleation step was performed prior to growth of the MTCVD Ti(C,N) layer. Oxidation and nucleation steps were performed prior to growth of the α-alumina layer.
(95) While the invention has been described in connection with various exemplary embodiments, it is to be understood that the invention is not to be limited to the disclosed exemplary embodiments, on the contrary, it is intended to cover various modifications and equivalent arrangements within the appended claims.