JPS6053748B2 - Manufacturing method of coated cemented carbide - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing coated cemented carbide.

TiC, TiN, which has wear resistance due to the cemented carbide surface.
So-called coated cemented carbide members coated with a thin layer of ceramics such as Ti(CN) and A12Oa are widely used in practical use as cutting tools that are superior to conventional cemented carbide members. Such coated cemented carbide is generally manufactured by the following method. Taking the case of coating TiC as an example, the raw material is TiC1.

After measuring and mixing the required amounts of , CH, and H, 1
Introduced into a reaction vessel heated to around 0 μC, TiC is precipitated and coated on the surface of the cemented carbide previously housed in the reaction vessel,
Coated cemented carbide is manufactured, and the gas after precipitation is then exhausted to the outside of the reaction vessel. A specific example of coating with TiC is shown in FIG. The CH and H2 whose flow rates were adjusted by the flow meters 1 and 2 pass through the TICI maintained at a predetermined temperature by the water bath 3 and the evaporator 4, thereby producing TiC1 at a predetermined ratio.

After being saturated, it is introduced into a reaction vessel 6 heated to a predetermined temperature by a resistance heating furnace 5. The gas introduced from the inlet M is deposited and coated with TiC on the surface of the cemented carbide previously housed in the reaction vessel 6, and is then exhausted from the exhaust port N to the cold trap 7 cooled by liquid nitrogen. At , unreacted raw materials and reaction by-products are collected and discharged into the atmosphere by a vacuum pump 8. Now, in such a manufacturing method, it is recognized that the deposition rate of TiC in the reaction vessel 6 is usually determined by the following conditions.

ri=niCPTiC1]ACPCH.

]. exp(-Q/RT)...1 set, however, :T
iC growth rate circle C14: Partial pressure PCH of TiC14 in the reaction gas.

: Partial pressure of CH in the reaction gas Q: Activation energy R: gas constant T: reaction temperature A, B, to: constant By the way, TiC1 in the axial direction of the reaction vessel 6.

Changes in the partial pressures of and CH are schematically shown in FIGS. 2 and 3. That is, TiC1 and CH4 in the reaction gas introduced into the reaction vessel 6 from the inlet M are T
The reaction follows the formula iC14+CH4→TiC+4HC1, and when TiC is deposited and coated on the cemented carbide, a part of TiCl4 and CH4 is consumed,
The partial pressures of TiCl4 and CH4 gradually decrease.

For this reason, as is clear from equation 1, the precipitation rate of TiC gradually decreases. Changes in the precipitation rate of TiC, which is the coating material, have a very important effect on the performance of the coated cemented carbide. That is, if the coating film is too thin, the inherent wear resistance effect of the coated cemented carbide will not be recognized, and if it is too thick, the wear resistance will improve but the toughness of the cemented carbide will decrease.
Taking a coated cemented carbide member for a cutting tool coated with TLC as an example, the thickness of the coating film is generally 2 to 15 p1, especially 4 to 1 p1.
It is said that 0μ is preferable, and the film thickness tolerance is usually within ±10% in industry.

For this reason, it is necessary to appropriately control the precipitation rate of the coating material depending on the use of the coated cemented carbide.

Conventionally, as a method for reducing the difference in precipitation rate between the inlet M side and the outlet N side, as described above, the temperature on the outlet N side of the reaction vessel 6 is made higher than that on the inlet port M side. By controlling the temperature distribution in the axial direction of 1
By controlling T in the equation, the deposition rate of the raw material gas in the reaction vessel 6 was kept uniform.

However, conventional methods had several drawbacks. In particular, (a) TlC particles precipitated by chemical vapor deposition become larger as the reaction temperature increases, so the TiC particles precipitated on the cemented carbide on the N side of the discharge port become larger, and the performance of the coated cemented carbide increases. Unfavorable things.

(b) The amount and composition of the decarburized layer formed at the interface between the base cemented carbide and the coating layer, which has the most important effect on the performance of the coated cemented carbide, is significantly affected by the reaction temperature. (c)
When coating Ti(CN), T1(CNO), etc., even if the composition of the reaction gas is the same, the coated Ti(CN) may differ from the C.I. of Ti(CNO) due to the difference in reaction temperature. l
5Nl or the ratio of C, N and O becomes different.

(d) Since there is a limit to the reaction temperature difference within the reaction vessel 6, the size of the device, especially the length from the inlet M to the discharge row N, is limited, making mass production difficult.

etc. acted as a serious impediment to the performance and industrializability of the final product. The present invention is an invention that eliminates the various drawbacks of the prior art as described above, and is a method for producing coated cemented carbide by chemical vapor deposition, in which the intake side and exhaust side of a reaction vessel where the coating reaction is carried out are alternately connected. This is a method for producing a coated cemented carbide, which is characterized in that the coating substance is coated on the cemented carbide by changing the flow direction of the raw material gas in the reaction vessel.

This will be explained below based on the drawings. FIG. 4 is a diagram showing an embodiment of the present invention, and FIGS.
Or when the reaction gas is introduced from the intake/exhaust port Q, Ti
It is a diagram showing changes in the partial pressures of Cl and CI (4).

In FIG. 4, CH4 and H2 whose flow rates were adjusted by flow meters 41 and 42 passed through a TiCl4 evaporator 44 maintained at a predetermined temperature by a water bath 43, thereby saturating a predetermined proportion of TlCl4. Thereafter, it is guided to the intake/exhaust port P by the three-way cock X, and after coating the cemented carbide with TiC in the reaction vessel 46, it is discharged from the intake/exhaust port Q, and guided to the cold trap 47 by the three-way cock Y.

In this case, in the reaction vessel 46, the partial pressures of TiCI4 and CI(i) decrease as the side approaches the intake/exhaust port Q from the intake/exhaust port P side, according to the solid lines in FIGS. 5 and 6. go.

Next, after a predetermined period of time, adjust the three-way cocks X and Y, and
The reaction gas that has passed through the iCl4 evaporator 44 is transferred to the intake and exhaust port P.
The guide to the reaction vessel 46 is cut off, guided to the intake/exhaust port Q, and the reaction vessel 46
After passing through the inside, it is discharged from the intake/exhaust port P and guided to the cold trap 47.

In this case, TiCl4 and C in the reaction vessel 46
The partial pressure of H4 approaches the direction of the dotted lines in FIGS. 5 and 6. Adjust these three-way cocks X and Y appropriately, and
By changing the flow of the reaction gas in the reaction vessel 46, it became possible to provide a uniform coating film on all the cemented carbide in the reaction vessel 46 while keeping the reaction temperature constant. FIG. 4 shows an embodiment of the present invention, and it is not necessary to use three-way cocks X and Y, but instead, as shown in FIG. P″, Q, Q″
The reaction vessel 76 is equipped with cocks 4, Z2, Z3, and
As long as it is possible to alternately switch between the intake side and the exhaust side of the engine, any method may be used.

Although the above-mentioned embodiments have mainly been described with reference to the case where TiC is coated, the present invention is not limited to TiC, but is applicable to all techniques for providing a coating film on cemented carbide by chemical vapor deposition.

The present invention makes it possible to easily prevent variations in the thickness of the coating film due to differences in coating speed, and further satisfies the mass productivity required for cemented carbide products.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of a conventional coated cemented carbide manufacturing apparatus. FIG. 2 is a partial pressure distribution diagram of TiCl4 in the axial direction of the reaction vessel 6 when the reaction gas is introduced from the inlet M. Third
The figure is a CH4 partial pressure distribution diagram, Figure 4 is a system diagram showing one embodiment of the present invention, and Figure 5 is a Ti
FIG. 6 is a partial pressure distribution diagram of CH4 when the present invention is used, and FIG. 7 is a system diagram showing another embodiment of the present invention. 1, 41, 71, 2, 42, 72...
...Flowmeter, 3,43,73...Water bath,
4,44,74...TiCl4 evaporator, 6,4
6,76...Reaction container, 7,47,77...
Cold trap, 8, 48, 88... Vacuum pump, M... Intake port, "N... Exhaust port, P, P", Q, Q"... ...Intake and exhaust ports, X, Y・
...Three-way cock, 4, Z2, Z3, 4...
·cock.

Claims (1)

[Claims] 1. In a method of manufacturing coated cemented carbide by chemical vapor deposition, the intake side and exhaust side of a reaction vessel in which the coating reaction is carried out are alternately switched to change the flow direction of the raw material gas in the reaction vessel. A method for producing coated cemented carbide characterized by: