JP3289842B2 - Coated WC based cemented carbide - Google Patents

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 having a coating formed on a cemented carbide tool suitable for cutting tools.

[0002]

2. Description of the Related Art Conventionally, in steel and casting processing, either dry cutting or wet cutting has been used depending on the application. As a conventional tool, a tool mainly deposited on a P-type (JIS-B4053-1987) surface by physical vapor deposition (PVD) has been mainly used. In recent years, there has been a shift to wet cutting due to processing problems.

That is, the phenomenon of dimensional change and material change of a workpiece can be suppressed by wet cutting.
In the case of conventional tools that are deposited on the P-type surface by the PVD method,
There has been a problem that the life and dimensional accuracy are inferior due to deformation and the like affected by heat cracks (heat cracks).

[0004]

However, high performance cutting tools are required for performing wet cutting. By the way, it has been used conventionally. PVD on P-type surface
In a tool deposited by the method, a large number of heat cracks occur in the tool due to a problem such as a heat cycle at the time of cutting, and the tool starts from a minute crack, develops into a large crack, and finally reaches a chip. As an adverse effect, the dimensional accuracy and tool life were reduced, and the tool could not be used. Therefore, paying attention to WC-based cemented carbide which is superior in strength to P-type cemented carbide,
The crack propagation in the process of changing from the generation of a heat crack to a large crack is suppressed by changing the particle size of the heat crack. It is another object of the present invention to provide a cutting tool which is subjected to a chemical vapor deposition method (CVD) having excellent adhesion to a substrate and has excellent heat crack resistance and chipping resistance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and focuses on the strength of WC-Co based cemented carbide, and uses WC as a hard phase in the 4a, 5a, 6a group. WC-based cemented carbide composed of one or more carbides and carbonitrides selected from the group consisting of 80-95% of a hard phase and the remainder consisting of Co and Ni bonded phases and unavoidable impurities. is there.

[0006] Further, as a hard phase, coarse WC of 7 μm or more
Α-phase (WC phase) composed of 10 to 30%, 30 to 40% of medium-grain WC of 3 to 7 μm, and fine WC of 3 μm or less, and TaC 0.20 selected from groups 4a, 5a, and 6a
6.00%, TiC 0.10 to 3.80%, and T
iC-TiN 0.50 to 3.75% with β phase [(WTi
Ta) C phase], and further adding 0.10 to 1.35% of ZrC as dispersion strengthening.

Further, the above-mentioned WC-base cemented carbide is used as a substrate, and the surface is coated with at least one layer of TiC, TiCN, TiN, Al ₂ O ₃ or the like.

[0008]

[Action] Attention is paid to the hard phase of cemented carbide to solve the problem of heat cracks occurring due to the effects of the thermal cycle during wet cutting and causing defects, and WC, which forms the hard phase,
Using TaC, TiC, TiC-TiN, and ZrC, the effect of suppressing crack propagation generated from heat cracks could be obtained.

First, coarse grains are used in WC to have the effect of suppressing crack propagation. TaC and TiC improve heat resistance and chemical reactivity. The structure was refined with TiC-TiN, and the heat-resistant plastic deformation property was improved with ZrC. Coarse-grain WC 7 μm or more 10-30%, medium-grain WC 3-7
With an average particle size of 30 to 40% and the remaining fine particles WC of 3 μm, there is an effect of suppressing crack propagation.

Next, a part of the WC in the hard phase is made up of 0.20 to 6.00% of tantalum carbide (TaC) and titanium carbide (T
iC) Replace with 0.10-3.80%. TaC 0.
20-6.00% and TiC 0.10-3.80%
And the ratio is (TaC / TiC) = 0.1 to 2.
5 improves heat resistance and chemical reaction resistance, and improves TiC-Ti
Microstructure refinement is performed with N of 0.50 to 3.75%, and dispersion strengthening in the binder phase is performed with ZrC of 0.10 to 1.35%, thereby suppressing heat-resistant plastic deformation. Further, if the coating is applied on the surface of the substrate, the temperature is further improved. The reasons for limiting the numerical values are described below.

When the coarse WC 7 μm is less than 10%, crack propagation is large, but when it exceeds 30%, the hardness (HR)
Since A) is insufficient, 10 to 30% is optimal. Medium grain WC
If 3 to 7 μm is less than 30%, crack propagation is large, and if it exceeds 40%, HRA is insufficient, so 30 to 40% is optimal. In addition, the effect of dispersion strengthening is recognized. By setting the remainder to be not more than 3 μm, the dispersion is strengthened in the hard phase, and the crack propagation and HRA are improved.

When the ratio of TaC and TiC exceeds 2.5, the transverse rupture strength is insufficient. When the ratio is less than 0.1, crater wear is a problem, so the ratio of 0.1 to 2.5 is optimal. TiC-T
When the iN exceeds 3.75%, the sinterability of the substrate deteriorates. 0.
If it is less than 50%, the effect of miniaturization is not recognized.

When ZrC is 0.10 to 1.35%, the heat-resistant plastic deformation property is remarkably improved. If it exceeds 1.35%, the transverse rupture strength decreases. If it is less than 0.10%, the effect of improving the heat plastic deformation is low. The optimum hard phase of the cutting tool is 80 to 95%. This is further improved by coating one or more layers on the surface of the WC-based cemented carbide substrate.

[0014]

【Example】

Example 1 A commercially available coarse WC and medium WC powder was used to change the WC particle size with a 92.0% WC-8.0% Co alloy as a base composition, and the remaining hard phase component and binder phase were used. It was blended with the constituent powder and wet mixed and pulverized. After a while, S
It was formed into a chip shape of EE42TN (JIS-B4120-1985), sintered at a temperature of 1350 to 1500 ° C., and ground to prepare. The surface is wrapped and mirror-finished, the microstructure is observed, classified according to the average particle size (major axis diameter + minor axis diameter) / 2, and the area is determined by each image processing device. In addition, the HRA measurement and the average crack length (a crack formed in a square of an indentation by a Vickers hardness tester) were measured. The results are also shown. From Table 1, it was possible to reduce the crack length by dispersing the coarse particles WC.

[0015]

[Table 1]

Example 2 TaC and TiC were added to the composition obtained in Example 1. The composition is 84.0-91.7% WC-0.3-8.0.
(Ta, Ti) C-8.0% Co. HRA was measured and the results are shown in Table 2. From Table 2, it was found that there was no adverse effect on HRA, and the problematic crack length did not increase.

[0017]

[Table 2]

Example 3 TiC-TiN was added to the composition obtained in Example 2. The composition is 89.0 to 91.5% (W, Ta, Ti) C
-0.5-3.0% TiC-TiN-80% Co. Table 3 shows the results as in Example 2. Table 3 shows that the microstructure was refined by adding TiC-TiN in which an increase in HRA was observed. The problematic cracks did not last.

[0019]

[Table 3]

Example 4 ZrC was added to the composition obtained in Example 3. The composition is 88.0-91.4% (W, Ta, Ti) C-0.5-
3.0% TiC-TiN-0.1 ~ 1.0% ZrC-
8.0% Co. Table 4 shows the results as in Example 2. Table 4 shows that the HRA was increased, and the dispersion was strengthened in the binder phase by the addition of ZrC. The problematic cracks did not last.

[0021]

[Table 4]

Example 5 After one or more layers are coated on the chip surface, the above-mentioned chip surface is attached to a milling cutter to perform wet cutting. The diameter of the milling cutter is 160 mm, and the cutting speed is 200 m / m.
in, feed per blade 0.2 mm, cut 2.
0mm, cutting fluid uses emulsion type water soluble cutting fluid, S50C (HB220 Brinell hardness) as work material
Was used.

Table 5 shows the results of the evaluation of the cutting time, in which a heat crack was generated due to the influence of the cutting and the chip was cut until the chip was broken. As shown in Table 5, the cutting performance showed a significant improvement in performance over the comparative product. The reason was that the effect of suppressing the progress of cracks was obtained.

The coating used in the examples was a coating coated by the CVD method. However, since the strength of the WC-based cemented carbide increased,
A material coated by the method D can sufficiently withstand use. Abrasion resistance can be improved by adding Al ₂ O ₃ to the coating layer.

[0025]

According to the present invention, the process from heat cracking to chipping is attenuated in wet cutting, which has been insufficient conventionally, and the tool life can be greatly improved.

[Table 5]

Claims (4)

(57) [Claims] 1. A WC-based cemented carbide comprising 80 to 95% by weight of a WC having a coating excellent in abrasion resistance on the surface of a substrate and the remainder: Co and Ni binder phases and unavoidable impurities. The WC particle size of the phase is 7 % or more in terms of area % from the microstructure on the polished surface.
%, 3 to 7 μm medium grain WC: 30 to 40%, remaining: 3 μm
A coated WC-based cemented carbide characterized by having fine grains WC of m or less. 2. The coated WC-based cemented carbide according to claim 1, wherein a part of WC in the hard phase is TaC: 0.20 to 0.20.
6.00% by weight , TiC: 0.10 to 3.80% by weight
And the ratio is (TaC / TiC) = 0.1-2.
A coated WC-based cemented carbide characterized by having been replaced by a ratio of 5. 3. The coated WC-base cemented carbide according to claim 2, wherein WC, TaC and TiN of the hard phase are partially replaced by T.
A coated WC-based cemented carbide characterized by replacing with iCN or TiN: 0.50 to 3.75% by weight . 4. The coated WC-base cemented carbide according to claim 3, wherein WC and TaC, TiC, TiC-
TiN and a part of TiN are converted to ZrC: 0.10 to 1.3.
A coated WC-based cemented carbide characterized by being replaced by 5% by weight .