Coated cutting tool

Abstract

A coated cutting tool includes a substrate and a coating layer formed onto the surface of the substrate. The coating layer contains an -type aluminum oxide layer. A residual stress value at the (116) plane of the -type aluminum oxide layer is greater than 0. A residual stress value at the (012) plane of the -type aluminum oxide layer is smaller than 0.

Claims

1. A coated cutting tool which comprises a substrate and a coating layer formed on a surface of the substrate, wherein the coating layer contains an -type aluminum oxide layer, a residual stress value of the -type aluminum oxide layer at a (116) plane is greater than 0, and a residual stress value of the -type aluminum oxide layer at a (012) plane is smaller than 0.

2. The coated cutting tool according to claim 1, wherein if the residual stress value of the -type aluminum oxide layer at the (116) plane is given by A, then A is 20A500 MPa, and if the residual stress value of the -type aluminum oxide layer at the (012) plane is given by B, then B is 800B100 MPa.

3. The coated cutting tool according to claim 1, wherein the residual stress value is a value measured by a sin.sup.2 method.

4. The coated cutting tool according to claim 1, wherein an average thickness of the -type aluminum oxide layer is 1 to 15 m.

5. The coated cutting tool according to claim 1, wherein the tool further comprises a Ti compound layer containing a compound of a Ti element and at least one element selected from the group consisting of C, N, O and B, and the Ti compound layer is formed between the substrate and the -type aluminum oxide layer.

6. The coated cutting tool according to claim 5, wherein the Ti compound layer contains a TiCN layer, and an atomic ratio of C based on a total of C and N [C/(C+N)] contained in the TiCN layer is 0.7C/(C+N)0.9.

7. The coated cutting tool according to claim 5, wherein an average thickness of the coating layer is 3 to 30 m, and an average thickness of the Ti compound layer is 2 to 15 m.

8. The coated cutting tool according to claim 1, wherein the substrate is a cemented carbide, cermet, ceramics or a cubic boron nitride sintered body.

9. The coated cutting tool according to claim 1, wherein if the residual stress value of the -type aluminum oxide layer at the (116) plane is given by A, then A is 20A500 MPa; if the residual stress value of the -type aluminum oxide layer at the (012) plane is given by B, then B is 800B100 MPa; and the residual stress value is a value measured by a sin.sup.2 method.

10. The coated cutting tool according to claim 1, wherein an average thickness of the -type aluminum oxide layer is 1 to 15 m; the tool further comprises a Ti compound layer containing a compound of a Ti element and at least one element selected from the group consisting of C, N, O and B, and the Ti compound layer is formed between the substrate and the -type aluminum oxide layer.

11. The coated cutting tool according to claim 10, wherein the Ti compound layer contains a TiCN layer, and an atomic ratio of C based on a total of C and N [C/(C+N)] contained in the TiCN layer is 0.7C/(C+N)0.9.

12. The coated cutting tool according to claim 11, wherein an average thickness of the coating layer is 3 to 30 m, and an average thickness of the Ti compound layer is 2 to 15 m.

13. The coated cutting tool according to claim 12, wherein the substrate is a cemented carbide, cermet, ceramics or a cubic boron nitride sintered body.

14. The coated cutting tool according to claim 1, wherein an average thickness of the coating layer is 3 to 30 m; an average thickness of the -type aluminum oxide layer is 1 to 15 m; the tool comprises a Ti compound layer formed between the substrate and the -type aluminum oxide layer; the Ti compound layer contains a TiCN layer; and an atomic ratio of C based on a total of C and N [C/(C+N)] contained in the TiCN layer is 0.7C/(C+N)0.9.

15. The coated cutting tool according to claim 14, wherein if the residual stress value of the -type aluminum oxide layer at the (116) plane is given by A, then A is 20A500 MPa, and if the residual stress value of the -type aluminum oxide layer at the (012) plane is given by B, then B is 800B100 MPa.

16. The coated cutting tool according to claim 15, wherein the substrate is a cemented carbide, cermet, ceramics or a cubic boron nitride sintered body.

17. The coated cutting tool according to claim 14, wherein the substrate is a cemented carbide, cermet, ceramics or a cubic boron nitride sintered body.

Description

EXAMPLES

(1) In the following, the present invention is explained by referring to Examples, but the present invention is not limited by these.

(2) According to the procedure mentioned below, a coated cutting tool (a sample) having a substrate and a coating layer formed onto the surface of the substrate was prepared. A sectional surface of the sample was observed by SEM at the neighbor of 50 m from the cutting edge of the prepared sample toward the center portion of the rake face of the prepared sample. A thickness of the coating layer of the coated cutting tool (the sample) was measured at the three portions, and an average value of the thickness of the measured three portions was obtained.

(3) The residual stress of the type aluminum oxide layer contained in the coating layer was measured by the sin.sup.2 method using an X-ray stress measurement apparatus. The residual stress of the type aluminum oxide layer was measured at the optional ten points in the coating layer, and an average value of the measured residual stresses was obtained.

(4) A cutting insert made of a cemented carbide having a JIS standard CNMA120408 shape with a composition of 93.6WC-6.0Co-0.4Cr.sub.3C.sub.2 (% by mass) was used as the substrate. After round honing was applied to the cutting blade ridge line portion of the substrate by a SiC brush, the surface of the substrate was washed.

(5) After washing the surface of the substrate, the substrate was conveyed to an external heating type chemical vapor deposition apparatus. At the inside of an external heating type chemical vapor deposition apparatus, a coating layer was formed onto the surface of the substrate. The formation conditions of the coating layer are shown in Table 1. The constitution and the average thickness of the coating layer are shown in Table 2.

(6) TABLE-US-00001 TABLE 1 Temper- Pressure Kind of coating layer ature ( C.) (hPa) Composition of starting materials (mol %) type Al.sub.2O.sub.3 1000 70 AlCl.sub.3: 2.7%, CO.sub.2: 3.3%, HCl: 2.5%, H.sub.2S: 0.3%, H.sub.2: 91.2% TiN 900 400 TiCl.sub.4: 3.2%, N.sub.2: 40%, H.sub.2: 56.8% TiC 1000 75 TiCl.sub.4: 2.4%, CH.sub.4: 4.6%, H.sub.2: 93% TiCN [C/(C + N): 0.6] 800 75 TiCl.sub.4: 3.0%, CH.sub.3CN: 0.3%, H.sub.2: 96.7% TiCN [C/(C + N): 0.7] 800 75 TiCl.sub.4: 2.5%, C.sub.3H.sub.6: 1.0%, N.sub.2: 20%, H.sub.2: 76.5% TiCN [C/(C + N): 0.8] 800 75 TiCl.sub.4: 2.5%, C.sub.3H.sub.6: 2.5%, N.sub.2: 20%, H.sub.2: 75% TiCN [C/(C + N): 0.9] 800 75 TiCl.sub.4: 2.5%, C.sub.3H.sub.6: 4.0%, N.sub.2: 10%, H.sub.2: 83.5% TiCN [C/(C + N): 0.95] 800 75 TiCl.sub.4: 2.5%, C.sub.3H.sub.6: 6.0%, N.sub.2: 5%, H.sub.2: 86.5% TiCNO 1000 100 TiCl.sub.4: 3.5%, CO: 0.7%, N.sub.2: 35.5%, H.sub.2: 60.3% TiAlCNO 1000 100 TiCl.sub.4: 3.8%, AlCl.sub.3: 1.5%, CO: 0.7%, N.sub.2: 35.2%, H.sub.2: 58.8% TiCO 1000 80 TiCl.sub.4: 1.3%, CO: 2.7%, H.sub.2: 96% TiAlCO 1000 80 TiCl.sub.4: 1.1%, AlCl.sub.3: 3.9%, CO: 2.8%, H.sub.2: 92.2%

(7) TABLE-US-00002 TABLE 2 Coating layer type Average Ti compound layer Al.sub.2O.sub.3 thickness First layer Second layer Third layer layer of whole Average Average Average Average coating Compo- thickness Compo- thickness Compo- thickness thickness layer Sample No. sition (m) sition (m) sition (m) (m) (m) Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product1 Present TiN 0.3 TiCN 2 TiCNO 0.5 2 4.8 product2 Present TiN 0.3 TiCN 13 TiCNO 0.5 13 26.8 product3 Present TiC 0.3 TiCN 8 TiCNO 0.5 8 16.8 product4 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product5 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product6 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product7 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product8 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product9 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product10 Present TiN 0.3 TiCN 8 TiAlCNO 0.5 8 16.8 product11 Present TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product12 Present TiC 0.3 TiCN 8 TiCO 0.5 8 16.8 product13 Present TiN 0.3 TiCN 8 TiAlCO 0.5 8 16.8 product14 Comparative TiN 0.2 TiCN 1 TiCNO 0.3 1 2.5 product1 Comparative TiN 0.5 TiCN 15 TiCNO 0.5 17 33.0 product2 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product3 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product4 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product5 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product6 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product7 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product8 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product9 Comparative TiN 0.3 TiCN 8 TiCNO 0.5 8 16.8 product10

(8) With regard to Present products 1 to 14, after forming the coating layer, the dry shot-blasting was applied to the rake face and the flank face, respectively, under the conditions shown in Table 3. At this time, when the rake face was to be processed, the flank face was masked so that the projection materials did not hit thereto. When the flank face was to be processed, the rake face was masked.

(9) With regard to Comparative products 1 to 9, after forming the coating layer, the dry shot-blasting or the wet shot-blasting was applied under the conditions shown in Table 4. With regard to Comparative product 10, neither the dry shot-blasting nor the wet shot-blasting was applied.

(10) TABLE-US-00003 TABLE 3 Average particle size of projection Projection Projection Shot- Projection materials speed angle Sample No. blasting materials (m) (m/sec) () Present Dry cBN 120 120 10 product 1 Present Dry cBN 100 120 5 product 2 Present Dry cBN 120 120 10 product 3 Present Dry cBN 120 120 10 product 4 Present Dry cBN 120 120 10 product 5 Present Dry cBN 120 120 10 product 6 Present Dry cBN 120 120 10 product 7 Present Dry cBN 120 120 10 product 8 Present Dry cBN 120 150 10 product 9 Present Dry cBN 120 100 10 product 10 Present Dry cBN 120 120 10 product 11 Present Dry cBN 120 120 10 product 12 Present Dry cBN 120 120 10 product 13 Present Dry cBN 120 120 10 product 14

(11) TABLE-US-00004 TABLE 4 Average particle size of projection Projection Projection Shot- Projection materials speed angle Sample No. blasting materials (m) (m/sec) () Comparative Dry cBN 120 120 60 product 1 Comparative Wet Al.sub.2O.sub.3 30 100 45 product 2 Comparative Wet Al.sub.2O.sub.3 30 100 45 product 3 Comparative Wet Al.sub.2O.sub.3 30 100 45 product 4 Comparative Dry Al.sub.2O.sub.3 120 120 45 product 5 Comparative Dry Al.sub.2O.sub.3 120 120 45 product 6 Comparative Wet Al.sub.2O.sub.3 30 100 45 product 7 Comparative Dry Al.sub.2O.sub.3 120 120 45 product 8 Comparative Dry Al.sub.2O.sub.3 120 120 60 product 9 Comparative No treatment product 10

(12) The residual stress of the type aluminum oxide layer was measured by the sin.sup.2 method using an X-ray stress measurement apparatus. The measured results of the residual stress of the type aluminum oxide layer are shown in Table 5.

(13) TABLE-US-00005 TABLE 5 type aluminum oxide layer Residual stress Residual stress value A (MPa) at value B (MPa) at Sample No. (116) plane (MPa) (012) plane (MPa) Present product 1 200 400 Present product 2 50 300 Present product 3 200 400 Present product 4 200 400 Present product 5 200 400 Present product 6 200 400 Present product 7 200 400 Present product 8 200 400 Present product 9 50 700 Present product 10 400 200 Present product 11 200 400 Present product 12 200 400 Present product 13 250 320 Present product 14 190 360 Comparative product 1 30 200 Comparative product 2 400 100 Comparative product 3 400 100 Comparative product 4 400 100 Comparative product 5 200 300 Comparative product 6 200 300 Comparative product 7 550 200 Comparative product 8 200 1000 Comparative product 9 100 900 Comparative product 10 730 620

(14) An atomic ratio of C based on the total of C and N [C/(C+N)] contained in the TiCN layer was measured by using EPMA. Specifically, an atomic ratio at the position of 50 m from the cutting edge of the coated cutting tool toward the center portion of the rake face was measured by EPMA.

(15) TABLE-US-00006 TABLE 6 TiCN Sample No. C/(C + N) Present product 1 0.8 Present product 2 0.8 Present product 3 0.8 Present product 4 0.8 Present product 5 0.7 Present product 6 0.9 Present product 7 0.8 Present product 8 0.8 Present product 9 0.8 Present product 10 0.8 Present product 11 0.8 Present product 12 0.8 Present product 13 0.75 Present product 14 0.6 Comparative product 1 0.8 Comparative product 2 0.8 Comparative product 3 0.6 Comparative product 4 0.95 Comparative product 5 0.8 Comparative product 6 0.8 Comparative product 7 0.8 Comparative product 8 0.8 Comparative product 9 0.8 Comparative product 10 0.8

(16) By using the obtained samples (tools), Cutting test 1 and Cutting test 2 were carried out. Cutting test 1 is a test to evaluate wear resistance of the tool. Cutting test 2 is a test to evaluate fracture resistance of the tool.

(17) [Cutting Test 1] Work piece material: FCD600 Shape of work piece material: Disc having 180 mmL20 mm (a square hole with 75 mm at the center of the disc) Cutting speed: 150 m/min Feed: 0.35 mm/rev Depth of cut: 2.0 mm Coolant: Used

(18) In Cutting test 1, the work piece material was cut using the sample to measure the life of the sample (tool). Specifically, the processing time until a maximum wear width of the flank face of the sample reached 0.3 mm was measured.

(19) [Cutting Test 2] Work piece material: FC200 Shape of work piece material: Disc having 180 mmL20 mm with two grooves having a width of 15 mm (a hole with 65 mm at the center of the disc) Cutting speed: 400 m/min Feed: 0.35 mm/rev Depth of cut: 2.0 mm Coolant: Used

(20) In Cutting test 2, the work piece material was cut using the sample to measure the life of the sample (tool). Specifically, the number of impacts until the sample was fractured or the maximum wear width of the flank face of the sample reached 0.3 mm was measured. The number of impacts means a number of times in which the sample and the work piece material have been contacted. When the number of impacts reached 20,000 times, the test was finished. Five specimens were prepared for each sample. With regard to each sample, the number of impacts was measured five times. An average value of the number of impacts which had been measured five times was calculated.

(21) TABLE-US-00007 TABLE 7 Cutting test 1 Cutting test 2 Wear test Fracture test Tool life Damaged Tool life Damaged Sample No. (min) state (times) state Present 45 Normal wear 18000 Fractured product 1 Present 35 Normal wear 20000 Normal wear product 2 Present 55 Normal wear 16000 Fractured product 3 Present 45 Normal wear 18000 Fractured product 4 Present 40 Normal wear 19000 Fractured product 5 Present 50 Normal wear 17000 Fractured product 6 Present 45 Normal wear 17000 Fractured product 7 Present 45 Normal wear 18000 Fractured product 8 Present 40 Normal wear 19500 Fractured product 9 Present 45 Normal wear 17000 Fractured product 10 Present 45 Normal wear 18000 Fractured product 11 Present 45 Normal wear 18000 Fractured product 12 Present 38 Normal wear 17000 Fractured product 13 Present 35 Normal wear 16500 Fractured product 14 Comparative 10 Normal wear 18000 Fractured product 1 Comparative 20 Fractured 3000 Fractured product 2 Comparative 15 Normal wear 12000 Fractured product 3 Comparative 25 Chipping 8000 Fractured product 4 Comparative 20 Peeling of 7000 Fractured product 5 coating film Comparative 30 Normal wear 11000 Fractured product 6 Comparative 45 Normal wear 5000 Fractured product 7 Comparative 20 Normal wear 18000 Fractured product 8 Comparative 25 Normal wear 17000 Fractured product 9 Comparative 35 Fractured 1500 Fractured product 10

(22) As shown in Table 7, wear resistance and fracture resistance of Present products are improved. Present products had longer processing times until these reached the tool life and had much number of impacts than those of Comparative products. From these results, it can be understood that the tool lives of Present products are markedly longer than those of Comparative products.

UTILIZABILITY IN INDUSTRY

(23) The coated cutting tool of the present invention has high wear resistance and excellent fracture resistance. The coated cutting tool of the present invention has longer life than those of the conventional tools, so that it has high utilizability in industry.