Hard coating, hard-coated tool, and their production methods

1. A hard coating comprising a lower layer formed by an fcc-based titanium aluminum nitride coating and an upper layer formed by an aluminum nitride coating having an hcp crystal system;

said upper layer having a columnar crystal structure,

said columnar crystals having an average transverse cross section diameter of 0.05-0.6 μm,

said lower layer having a columnar crystal structure, and

a ratio of an X-ray diffraction peak value Ia(002) of (002) planes to an X-ray diffraction peak value Ia(100) of (100) planes in said upper layer meeting the relation of Ia(002)/Ia(100)≥6.

2. The hard coating according to claim 1 , wherein a ratio of a merged X-ray diffraction peak value It(111)Ia(101) of the (111) planes of said lower layer and the (101) planes of said upper layer to said Ia(100) meets the relation of It(111)Ia(101)/Ia(100)≥1.5, in an X-ray diffraction angle 2θ range of 36° to 39°.

3. The hard coating according to claim 1 , wherein a ratio of a merged X-ray diffraction peak value It(111)Ia(101) of the (111) planes of said lower layer and the (101) planes of said upper layer to the X-ray diffraction peak value It(200) of the (200) planes of said lower layer meets the relation of It(111)Ia(101)/It(200)≥1.5, in an X-ray diffraction angle 2θ range of 36-39°.

4. The hard coating according to claim 1 , wherein 30% or more of lattice fringes are continuous in an interface between said lower layer and said upper layer.

5. A hard-coated tool having the hard coating recited in claim 1 formed on a substrate.

6. A method for producing the hard coating recited in claim 1 by a chemical vapor deposition method, comprising

(1) using a mixture gas A 1 comprising a TiCl 4 gas, an AlCl 3 gas, an N 2 gas and an H 2 gas, and a mixture gas B 1 comprising an N 2 gas, an NH 3 gas and an H 2 gas, as a first starting material gas for forming said lower layer; and

(2) using a mixture gas A 2 comprising an AlCl 3 gas, an N 2 gas and an H 2 gas, and a mixture gas B 2 comprising an NH 3 gas, an N 2 gas and an H 2 gas, as a second starting material gas for forming said upper layer, wherein said lower layer is formed at a forming pressure of 3-6 kPa and a forming temperature of 750-830° C.; and said upper layer is formed at a forming pressure of 3-5 kPa and a forming temperature of 750-850° C.

7. The method for producing a hard coating according to claim 6 , wherein

said first starting material gas is composed of a mixture gas A 1 having a composition comprising 0.02-0.31% by volume of TiCl 4 gas, 0.15-0.8% by volume of an AlCl 3 gas, and 3-40% by volume of an N 2 gas, the balance being an H 2 gas, and a mixture gas B 1 having a composition comprising 0.4-1.9% by volume of an NH 3 gas, and 2-26% by volume of an N 2 gas, the balance being an H 2 gas, with the total amount of the TiCl 4 gas, the AlCl 3 gas, the NH 3 gas, the N 2 gas, and the H 2 gas as 100% by volume, a volume ratio H 2 (A 1 )/H 2 (B 1 ) of an H 2 gas in said mixture gas A 1 to an H 2 gas in said mixture gas B 1 being 1-5; and

said second starting material gas is composed of a mixture gas A 2 having a composition comprising 0.5-1.4% by volume of an AlCl 3 gas, and 10.6-30.6% by volume of an N 2 gas, the balance being an H 2 gas, and a mixture gas B 2 having a composition comprising 0.6-0.95% by volume of an NH 3 gas, and 10.6-30.6% by volume of an N 2 gas, the balance being an H 2 gas, with the total amount of the AlCl 3 gas, the NH 3 gas, the N 2 gas and the H 2 gas as 100% by volume, a volume ratio H 2 (A 2 )/H 2 (B 2 ) of an H 2 gas in said mixture gas A 2 to an H 2 gas in said mixture gas B 2 being 0.3-3.

8. The method for producing a hard coating according to claim 6 , wherein

a chemical vapor deposition apparatus comprising first and second pipes rotating around a rotation axis O is used;

said first pipe has first nozzles;

said second pipe has second nozzles;

the distance H 1 between the openings of said first nozzles and said rotation axis O is larger than the distance H 2 between the openings of said second nozzles and said rotation axis O; and

(a) said mixture gases A 1 , A 2 are successively ejected from said first nozzles, and said mixture gases B 1 , B 2 are successively ejected from said second nozzles, or (b) said mixture gases B 1 , B 2 are successively ejected from said first nozzles, and said mixture gases A 1 , A 2 are successively ejected from said second nozzles.

9. The method for producing a hard coating according to claim 8 , wherein a ratio (H 1 /H 2 ) of said distance H 1 to said distance H 2 is in a range of 1.5-3.

10. The method for producing a hard coating according to claim 6 , wherein said lower layer is formed at a forming pressure of 3-6 kPa and a forming temperature of 750-900° C.; and said upper layer is formed at a forming pressure of 3-5 kPa and a forming temperature of 750-850° C.

11. A method for producing the hard-coated tool recited in claim 5 , wherein

(1) a first starting material gas composed of a mixture gas A 1 comprising a TiCl 4 gas, an AlCl 3 gas, an N 2 gas and an H 2 gas, and a mixture gas B 1 comprising an N 2 gas, an NH 3 gas and an H 2 gas is introduced into a chemical vapor deposition apparatus containing substrates, to form said lower layer; and then

(2) a second starting material gas composed of a mixture gas A 2 comprising an AlCl 3 gas, an N 2 gas and an H 2 gas, and a mixture gas B 2 comprising an NH 3 gas, an N 2 gas and an H 2 gas is introduced into a chemical vapor deposition apparatus containing substrates, to form said upper layer, wherein said lower layer is formed at a forming pressure of 3-6 kPa and a forming temperature of 750-830° C.; and said upper layer is formed at a forming pressure of 3-5 kPa and a forming temperature of 750-850° C.

12. The method for producing a hard-coated tool according to claim 11 , wherein

said first starting material gas is composed of a mixture gas A 1 having a composition comprising 0.02-0.31% by volume of a TiCl 4 gas, 0.15-0.8% by volume of an AlCl 3 gas, and 3-40% by volume of an N 2 gas, the balance being an H 2 gas, and a mixture gas B 1 having a composition comprising 0.4-1.9% by volume of an NH 3 gas, and 2-26% by volume of an N 2 gas, the balance being an H 2 gas, with the total amount of the TiCl 4 gas, the AlCl 3 gas, the NH 3 gas, the N 2 gas, and the H 2 gas as 100% by volume, a volume ratio H 2 (A 1 )/H 2 (B 1 ) of an H 2 gas in said mixture gas A 1 to an H 2 gas in said mixture gas B 1 being 1-5; and

said second starting material gas is composed of a mixture gas A 2 having a composition comprising 0.5-1.4% by volume of an AlCl 3 gas, and 10.6-30.6% by volume of an N 2 gas, the balance being an H 2 gas, and a mixture gas B 2 having a composition comprising 0.6-0.95% by volume of an NH 3 gas, and 10.6-30.6% by volume of an N 2 gas, the balance being an H 2 gas, with the total amount of the AlCl 3 gas, the NH 3 gas, the N 2 gas and the H 2 gas as 100% by volume, a volume ratio H 2 (A 2 )/H 2 (B 2 ) of an H 2 gas in said mixture gas A 2 to an H 2 gas in said mixture gas B 2 being 0.3-3.

13. The method for producing a hard-coated tool according to claim 11 , wherein

a chemical vapor deposition apparatus comprising first and second pipes rotating around a rotation axis O is used;

said first pipe comprises first nozzles;

said second pipe comprises second nozzles;

the distance H 1 between the openings of said first nozzles and said rotation axis O is larger than the distance H 2 between the openings of said second nozzles and said rotation axis O; and

(a) said mixture gases A 1 , A 2 are successively ejected from said first nozzles, and said mixture gases B 1 , B 2 are successively ejected from said second nozzles, or (b) said mixture gases B 1 , B 2 are successively ejected from said first nozzles, and said mixture gases A 1 , A 2 are successively ejected from said second nozzles.

14. The method for producing a hard-coated tool according to claim 13 , wherein a ratio (H 1 /H 2 ) of said distance H 1 to said distance H 2 is in a range of 1.5-3.