JPS6142788B2 - - Google Patents

Description

[Detailed description of the invention]

IVa on the surface of cemented carbide, especially WC-Co, WC-TiC-Co alloys, in which one or more carbides, nitrides, carbonitrides of IVa, Va, VIa group elements are combined with one or more iron group metals. , Va, carbides and nitrides of group VIa elements,
It is known that so-called coated cemented carbide tools coated with carbonitride, Al ₂ O ₃ or ZrO ₂ exhibit higher wear resistance than uncoated cemented carbide tools. As a result of careful consideration of the properties of these coated cemented carbide tools, the inventors have noticed that the tool life is often shortened due to rapid wear and chipping at the very beginning of cutting. Therefore, we investigated various causes of end of life at this early stage, and found that cracks occur on the surface of the coating film, the cracks coalesce, and the coating layer locally falls off, causing damage to the surrounding coating layer. This was thought to be due to the progression of The inventors have studied various ways to avoid this and achieve the original performance of the coating film, and have found that it is effective if the outer surface of the coated cemented carbide contains a coating layer containing free carbon. I discovered that. In other words, the coating layer in which free carbon coexists suppresses grain growth and forms a fine-grained structure, making it difficult for the cracks that occur when the cutting edge first hits the workpiece to propagate.
It was also thought that free carbon played the role of a buffer to stop the propagation of cracks. Free carbon is
The content is preferably 0.01 to 40%, particularly 0.01 to 10% by volume, although it varies depending on the type of the coating layer.
Below this range, the effect of the present invention is weak, and above this range, the strength of the coating layer decreases, which is not preferable.
As the layer containing free carbon, Ti carbide,
In addition to Al oxides, carbides of IVa, Va, and VIa groups,
Although oxides have the effect of the present invention, these two layers are most preferred from the viewpoint of strength and coexistence of free carbon. Moreover, the thickness of the coating layer is preferably 0.5 to 10 μm. Below 0.5μ,
It is not effective in preventing propagation of cracks, and if it exceeds 10μ, the strength of the coating will decrease. As a method of coating a layer containing free carbon,
Any method such as CVD or plasma CVD may be used. Next, an example will be explained. Example 1 ISO, MIO cemented carbide coated with 6μ of TiC The surface of a coated cemented carbide tool (shape SNMG432) was coated with 0.1μ, 5μ, and 15μ TiC layers containing 0.5% free carbon by vapor deposition. . (A, B, C) For comparison, cutting tests were conducted using a regular TiC coated chip (A) under the following conditions. Work material: S55C forged material Cutting speed: 130 to 160 m/min Depth of cut: 0.5 to 3.0 mm Feed: 0.35 mm/rev Cutting time: 3 minutes Looking at the damage state of the 50 cutting edge, D is 45 cutting edge Chipping occurred, and 30 of the cutting edges expired within 1 minute. On the other hand, for A, 35 cutting edges were chipped, and 20 cutting edges reached the end of their life within 1 minute, and for C, 30 cutting edges chipped, and 15 cutting edges reached the end of their life within 1 minute. In case B, chipping occurred on 5 cutting edges, and only 1 cutting edge had a life span of 1 minute or less. Example 2 ISO, MIO cemented carbide with 5μ TiC as inner layer,
As an outer layer, 1μ of Al ₂ O ₃ was coated by CVD method, and 1μ of free carbon was added on top as in Example 1.
Covered with ₃ layers of Al ₂ O. The amount of free carbon is 0,0.05,
5, 10, 30, and 50%, and tests were conducted using these chips under the following conditions. Work material: FC-30 Cutting speed: 180~220m/min Depth of cut: 0.8~7mm Feed: 0.32mm/rev Table 1 shows the test results.

【table】

[Table] Example 3 ISO-M10 cemented carbide (model number SNMN432)
Using 13.56MHZ RF wave plasma CVD equipment
As an inner layer with a mixed gas of H2, TiCl4, and CH4
TiC was coated to a thickness of 0.5μ. Next, using a mixed gas of H2 and CH4, carbon with high hardness is coated in scattered islands, and on top of this, H2, TiCl4, CH4
TiC was coated with a mixed gas of The operation of precipitating this high-hardness carbon and covering it with TiC was repeated two more times to adjust the total film thickness to 6 μm. At this time, the high-hardness carbon coating treatment time and the TiC coating treatment time were increased or decreased, and the proportion of high-hardness free carbon in the TiC coating film was set to 0, 0.05, 5, 15, 30, 40, and 50%. . Using these chips, cutting tests were conducted under the following conditions. Covering material: FC-25 Cutting speed: 200m/min Depth of cut: 3.0mm Feed: 0.36mm/rev Cutting time: 3 minutes The test results are shown in Table 2. The values in the table indicate the number of cutting edges where chipping occurred among 50 cutting edges, and the smaller the number, the better the performance.

[Table] Example 4 Using a resistance heating furnace for ISO-M10 cemented carbide,
At 1000℃, 5% by volume TiCI4, 5% by volume CH4, the balance
After generating TiC of 4 μm using H2 gas at a pressure of 60 torr, further layer Al203 of 3 μm on top of it using 5 volume% AlCl3, 5 volume% CO2, and a residual H2 gas pressure of 30 torr.
Coated. Subsequently, TiCl4 was held at a pressure of 30 torr for 1 hour in 0.1% by volume, 80% by volume CH4, and residual H2 gas. When such a chip was observed from the surface using X-ray analysis or a scanning electron microscope, it was found that a 1 μm thick layer in which TiC and 8% free carbon coexisted was formed. When a chip not according to the present invention (3 μm Al2 03 outer layer, 5 μm TiC inner layer) and a product according to the present invention were tested under the cutting conditions of Example 2, chipping occurred in the chip not according to the present invention when cutting 10 pieces, but this With the invented product, no chipping occurred even when cutting 20 pieces. Example 5 A chip made of ISO-M10 cemented carbide coated with 5 μm of TiC was heated to 1000°C, and then mixed with 5 volume% AlCl3, 5 volume% CO2, 10 volume% CH4, and the rest.
3μm Al2 03 at 30torr in a mixed atmosphere of H2 gas
coated. When this Al2 03 film was analyzed by ESCA, 1% C was detected. The particle size of the alumina film produced by the product of the present invention was 0.5 μm or less, whereas the particle size of the alumina film not produced by the present invention was as large as 3 μm. Example 6 In Example 5, the reaction gases CO2 and CH4 were alternately introduced at 0% and 5% (or 10%) for 5 minutes, and the same operation was repeated for 3 hours. When such a coating film was examined, it was found that 2 μm of Al2
Free C was scattered in 03, and its amount was 0.02%. Inventive product and commercially available product (2 μm Al203 outer layer, 5 μm
In Example 2, a cutting test was conducted on the mTiC inner layer). As a result, the product of the present invention showed approximately twice the lifespan of the commercially available product. In addition, commercially available products have reached the end of their service life due to chipping of the cutting edge.

Claims (1)

[Claims] 1. A coating layer on a cemented carbide, with an outer layer made of Ti carbide or Al oxide containing 0.01 to 40% by volume of free carbon, and an inner layer made of Ti, Zr, Hf, V, Nb. ,Ta,
One or more of carbides, nitrides, carbonitrides of Cr, Mo, and W, or their compounds and
A coated cemented carbide tool comprising one or more selected from Al203 and Zr02, and having a thickness of 0.5 to 10μ. 2. The coated cemented carbide tool according to claim 1, characterized in that the free carbon-containing Ti carbide and Al oxide layer contains 0.01% free carbon.