JP2000334608A - Cutting insert and manufacture of same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the toughness characteristic of cutting inserts for steel machining that include a cemented carbide body and a coating. SOLUTION: A cemented carbide body comprises WC, Co in an amount of 5 to 12% by mass, and cubic carbide of Ta, Ti and W in an amount of 3 to 11% by mass. The content of Nb is not more than 0.1% by mass. A Ta/Ti ratiio is between 1.0 and 4.0. The binder phase of Co is alloyed more with W so that a CW ratio lies between 0.75 and 0.95. The cemented carbide body has a surface region of a thickness of 5 to 50 μm which has the binder phase enriched and is substantially free of a gamma phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cemented carbide cutting insert which is particularly useful for turning operations of steel or stainless steel, and is particularly suitable for operations requiring high requirements regarding the toughness characteristics of the insert. Cemented carbide inserts simultaneously produce excellent toughness properties and good plastic deformation resistance,
It has a surface region having an elemental composition different from the bulk composition.

[0002]

2. Description of the Related Art Modern high performance cutting tools are required to have high wear resistance, high toughness characteristics and good composition deformation resistance. Improving the toughness behavior of the cutting insert
Although this can be achieved by increasing the WC grain size and / or increasing the overall binder phase content, such a change results in a significant loss of compositional deformation resistance at the same time.

[0003] A method for improving the toughness behavior by introducing into the insert an essentially gamma-phase-free, binder-phase-enriched surface zone having a thickness of about 20 to 40 μm by means of a so-called gradient sintering technique. Is, for example, U.S. Pat.
277,283, 4,497,874, 4,548,786, 4,64
0,931, 5,484,468, 5,549,980, 5,649,
Nos. 279 and 5,729,823. A feature of these patents is that there is no gamma phase in the surface region and the binder phase is enriched.

[0004]

By maintaining the ratio of Ta to Ti in a specific range and maintaining a high W alloyed binder phase, the composition of the optimized gamma phase, ie, WC, In particular, it has been shown that the gamma phase consisting of only TaC and TiC can significantly improve the toughness properties of the graded sintered cutting insert without loss of compositional deformation resistance.

[0005]

According to the present invention, a thickness of 5 mm is provided.
Bound phase enrichment of .about.50 .mu.m, preferably 10-30 .mu.m, essentially free of gamma phase and having an average bound phase content (by volume) in the range of 1.2 to 2.0 times the bulk bonded phase content. Provided is a coated cemented carbide insert that includes a textured surface region. The gamma phase consists essentially of TaC and TiC and WC dissolved in the gamma phase during some sintering. The ratio Ta / Ti is
It is 1.0 to 4.0, preferably 2.0 to 3.0.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The binder phase is high and W is alloyed. The W content in the binder phase can be expressed as CW ratio = M _S / ((% by weight of Co) × 0.0161), where M _S is the measured saturation magnetization of the cemented carbide body at kA / m. , Co mass% is the mass ratio of Co in the cemented carbide. The CW ratio takes a value of 1 or less, and the smaller the CW ratio, the higher the W content in the binder phase. If the CW ratio is in the range of 0.75 to 0.95, preferably 0.80 to 0.85,
The present invention has been shown to improve cutting performance.

The invention has a composition of a binder phase consisting of 5 to 12, preferably 9 to 11% by weight of Co, 3 to 11, preferably 7 to 10% by weight of TaC + TiC and the balance of WC. Applicable to cemented carbide. The Nb content should not exceed 0.1% by weight. The mass ratio Ta / Ti is 1.0 to 4.0, preferably 2.0 to 3.
Should be 0. WC has an average grain size of 1.0 to 4.0 μm, preferably 1.5 to 3.0 μm. The cemented carbide body may contain small amounts of less than 1% by volume of η phase (M ₆ C).

The insert according to the invention is more basically
For example, U.S. Patent Nos. 5,766,782, 5,654,035, 5,
No. 674,564 or No. 5,702,808, a 3 to 12 μm columnar TiCN layer, followed by 1 to 8
μm thick Al ₂ O ₃ layer, preferably comprising a κ-Al ₂ O ₃ layer and preferably an outermost thin layer of TiN, the TiN layer preferably being brushed or blasted. Removed at the cutting edge.

By applying coatings of various thicknesses on the cemented carbide body according to the present invention, the properties of the coated insert can be optimized to meet specific cutting conditions. In one embodiment, a cemented carbide insert made in accordance with the present invention comprises a coating of 6 μm TiCN, 5 μm Al ₂ O ₃ and 1 μm TiN. This coated insert is particularly suitable for working with steel. In another embodiment, a cemented carbide insert made in accordance with the present invention comprises 4 μm TiCN, 2 μm Al ₂ O ₃ and 1 μm Ti
N coating is provided. This coating is particularly suitable for cutting operations on stainless steel.

SUMMARY OF THE INVENTION The present invention relates to a binder phase of Co, WC, and Ta having a binder phase enriched surface region that is essentially free of a gamma phase.
The present invention also relates to a method for manufacturing a cutting insert including a cemented carbide substrate made of a gamma phase of Ti and Ti, and a coating. 5-12,
A bonded phase preferably consisting of 9-11% by weight of Co;
1, preferably 7 to 10% by mass of TaC + TiC, 1.0 to 4.0%
A WC having an average grain size of preferably 1.5 to 3.0 .mu.m. The Nb content should not exceed 0.1% by weight. Mass ratio Ta / Ti is 1.0
4.04.0, preferably 2.0-3.0. A well-controlled amount of nitrogen must be added by carbonitride powder and / or during the sintering process through a sintering gas atmosphere. The amount of nitrogen added determines the rate of dissolution of the cubic phase during the sintering process, and thus the overall distribution of elements in the solidified cemented carbide. The optimum amount of nitrogen added depends on the composition of the cemented carbide, in particular on the amount of the cubic phase, and varies between 0.6 and 2.0% of the mass of the elements Ti and Ta. The exact conditions will also depend in part on the design of the sintering equipment used. It is up to the skilled artisan to determine whether the required cemented carbide surface area has been obtained and to modify the nitrogen addition and sintering conditions in accordance with the present invention to achieve the desired results.

[0011] The raw materials are mixed with the compression molding agent and optionally with W to obtain the desired CW ratio, the mixture is milled and spray dried to obtain a powdered material having the desired properties. Next, the powder material is molded and sintered.
The sintering is performed at a temperature of 1300-1500 ° C. in a controlled atmosphere of about 5 × 10 ³ Pa (50 mbar) and then cooled. After conventional post-sintering treatment, including rounding of the cutting edge, a hard wear-resistant coating according to the preceding description is deposited by CVD or MT-CVD (medium temperature CVD).

[0012]

EXAMPLES Example 1 A) 9.9% by weight of Co, 6.0% by weight of TaC, 2.5% by weight of
TiC, less than 0.1 wt% NbC, and 0.3 wt% TiN
Cemented carbide turning inserts of the type CNMG 120408-PM and SNMG 120412-PR, having a composition with the balance of WC with an average grain size of 2.0 μm, were made according to the invention. Nitrogen
TiCN was added to the cemented carbide powder. Sinter about 5 × 10 ³
The test was performed at 1450 ° C. in an atmosphere consisting of Ar at a total pressure of Pa.

[0013] Observation of the metallographic structure revealed that the prepared insert had a 15 µm gamma phase-free region. FIG. 1 shows a graph of Co enrichment near the surface measured by image analysis techniques. Co was enriched to a peak concentration of 1.3 times the bulk content. The saturation magnetization was measured and used to calculate the CW value. An average CW value of 0.81 was obtained.

Following conventional coating pretreatments such as cutting edge honing, cleaning, etc., the MTCVD technique (process temperature 850)
° C, using CH ₃ CN) as the carbon / nitrogen source
The insert was coated by CVD with a thin layer of less than 1 .mu.m, followed by a 6 .mu.m thick layer of columnar grain TiCN. In a subsequent manufacturing step of the same coating step, a 5 μm thick κ-Al ₂ O ₃ layer was deposited according to US Pat. No. 5,674,564. On top of the κ-Al ₂ O ₃ layer, a 1.0 μm TiN layer was deposited. The coated insert was brushed to smoothly remove the TiN coating from the cutting edge.

B) 10.0% by weight of Co, 2.9% by weight of TaC,
3.4% by mass of TiC, 0.5% by mass of NbC, and 0.2% by mass
A cemented carbide turning insert of the type CNMG 120408-PM and SNMG 120412-PR was produced, having a composition of TiN and the rest of WC with an average grain size of 2.1 μm. The insert was sintered in the same manner as in A. Observation of the metallographic structure showed that the prepared insert had a region containing no gamma phase of 15 μm. The saturation magnetization was measured and used to calculate the CW value. An average CW value of 0.81 was obtained. The insert was subjected to the same pre-coating treatment as in A, coated with the same coating treatment and brushed as in A.

C) 10.0% by weight of Co, 3.0% by weight of TaC,
6.3% by mass of ZrC and WC with an average grain size of 2.5 μm
CNMG 120408-PM and SNMG 120 having a composition with the balance of
A 412-PR cemented carbide turning insert was manufactured. Observation of the metallographic structure indicated that the prepared insert had a 12 μm region free of the gamma phase. The saturation magnetization was measured and used to calculate the CW value. An average CW value of 0.79 was obtained. The insert was subjected to the same pre-coating treatment as in A, coated with the same coating treatment and brushed as in A. Example 2 Inserts of A, B and C were evaluated for toughness in a longitudinal turning operation with interrupted cutting.

Material: Carbon steel SS1312 Cutting data: Cutting speed 130 m / min Cutting depth 1.5 mm Feed starts at 0.15 mm and increases at 0.10 mm / min until blade breaks Evaluate each of 8 cutting edges Insert shape : CNMG 120408-PM Result: Average feed in case of breakage Insert A 0.31 mm / rotation Insert B 0.22 mm / rotation Insert C 0.22 mm / rotation Example 3 In the direction turning operation, the plastic deformation resistance was evaluated.

[0018] Plastic deformation was measured as a depression in the cutting edge at the nose of the insert.

Results: Indentation of cutting edge (μm) Insert A 49 Insert B 63 Insert C 62 Example 4 A test was carried out in the production of a rear shaft for trucks. The A and C inserts were evaluated in three types of turning operations with high toughness requirements for interrupted cutting. The insert was used until the cutting edge was broken. SNMG
An insert of type 120412-PR was used.

Results Number of parts machined Operation 1 2 3 Insert A 172 219 119 Insert B 20 11 50 Examples 2, 3 and 4 show that the insert A according to the invention has Shows significantly better toughness, with some improved compositional deformation resistance.

[0021]

According to the present invention, the toughness characteristics of a gradient sintered cutting insert can be significantly improved without loss of compositional deformation resistance.

[Brief description of the drawings]

FIG. 1 shows a graph of Co enrichment near the surface as measured by image analysis techniques.

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Claims (10)

[Claims] 1. A cutting insert for machining steel including a cemented carbide body and a coating, wherein the body comprises WC, 5 to 12% by mass of Co, and 3 to 11% by mass.
With Ta, Ti and W cubic carbides, and the Nb content is
0.1% by mass or less, the ratio Ta / Ti is 1.0 to 4.0,
o The cemented carbide body is alloyed high with W such that the binder phase has a CW ratio of 0.75 to 0.95, and the cemented carbide body has a binder phase enriched essentially gamma phase free surface area of 5 to 50 μm thickness. Cutting insert characterized by having. 2. The cutting insert according to claim 1, wherein the thickness of the surface region is 10 to 30 μm. 3. The cutting insert according to claim 1, wherein the Co content is 9 to 11% by mass. 4. The cutting insert according to claim 1, wherein the content of TiC and TaC is 7 to 10% by mass. 5. The method according to claim 1, wherein the coating has a columnar structure of 3 to 12 μm.
And CN layer, characterized in that it comprises a the Al ₂ O ₃ layer of 1~8μm subsequent cutting insert according to any one of claims 1 to 4. 6. The cutting insert according to claim 1, wherein the Al ₂ O ₃ layer is κ-Al ₂ O ₃ . 7. The cutting insert according to claim 1, wherein the coating comprises an outermost layer of TiN. 8. The cutting insert according to claim 1, wherein the TiN layer is removed at a cutting edge by brushing or blasting. 9. The cutting insert according to claim 1, wherein the average WC grain size is 1.0 to 4.0 μm. 10. A method for producing a cutting insert comprising a cemented carbide substrate having a binder phase enriched surface region and a coating, wherein the substrate comprises a Co binder phase, WC and a cubic carbonitride phase. Wherein the binder phase-enriched surface region is essentially free of the cubic carbonitride phase and has a substantially constant thickness over the periphery of the insert. 5 to 12, preferably 9 to 11% by weight of Co and 3 to 1
A powder mixture is prepared comprising 1, preferably 7 to 10% by weight of a cubic carbide of Ta and Ti, wherein nitrogen is added in an amount of 0.6 to 2.0% by weight of said Ta and Ti, Mixing the powder with a compression molding agent and optionally W to obtain a CW ratio, milling the mixture into a powdered material having the desired properties, and spray drying, shaping, and about 5 × In a controlled atmosphere of 10 ³ Pa, the powder material is sintered at a temperature of 1300 to 1500 ° C., then cooled, subjected to a conventional post-sintering treatment including rounding of the cutting edge, and hardened by CVD or MTCVD. A method for manufacturing a cutting insert, characterized by applying a wear-resistant coating of (1).