JPS5911663B2 - Manufacturing method for surface-coated cemented carbide parts - Google Patents

Description

[Detailed description of the invention] The base material is a so-called cemented carbide in which carbides and/or carbonitrides of Ti, Z, Hf, V, Nb, Ta, C, Mo, and W are combined with iron group metals, Various hard compounds on the surface,
For example, so-called coated chips, which are coated with Ti, Zr, and Hf carbides and carbonitride pentoxides to a thickness of several microns, have both the toughness of the base material and the wear resistance of the surface, and are superior to conventional ultra-thin cutting tools. It is a widely known fact that it has better performance than hard metals.

An object of the present invention is to stably provide such a coated chip with further improved characteristics.

Various hard coatings are typified by titanium carbide, so titanium carbide will be described below as an example.

Ti carbide, ■5 To coat cemented carbide with carbonitride, Ti halide (generally titanium tetrachloride),
A so-called chemical process in which titanium carbide and titanium carbonitride are precipitated from a gas mixture of hydrocarbon (generally methane), nitrogen and hydrogen gas at a predetermined ratio at a high temperature of around 1,000°C to coat the super 30 hard alloy. A vapor deposition method is used. Titanium carbonitride is similar to titanium carbide, so titanium carbide will be described below as an example.

The 35 reaction process of the precipitation reaction of titanium carbide by the chemical vapor deposition method described above is very complicated, but it can be easily explained by the following two steps: generation of free titanium according to equation 1 and carbonization of free titanium according to equation 2. It will be done.

TiCl4+2H2→Ti+4HC1・・・・・・・・・
・・・・・・1Ti+C-+TiC・・・・・・・・・・・・
...The carbonization of free titanium in Type 22 is carried out by free carbon generated by decomposition of hydrocarbons in the mixed gas and carbon supplied from the cemented carbide matrix.

When the hydrocarbon concentration in the mixed gas is low, and most of the hydrocarbons required to generate titanium carbide are supplied by diffusion of carbon in the cemented carbide matrix, a brittle decarburized layer called the η phase forms immediately below the titanium carbide coating layer. is formed, which significantly impairs the toughness of the coating chip. When the hydrocarbon concentration in the mixed gas is increased, most of the carbon necessary for titanium carbide production is supplied from the gas phase.
The above η phase also hardly exists.

Although it is possible to make a coated chip, when the hydrocarbon concentration exceeds a certain level, free carbon is generated in the coating film, which also significantly impairs the toughness and wear resistance of the coated chip. Furthermore, in a coating chip in which most of the carbon required to generate titanium carbide is supplied from the gas phase, flaking tends to occur between the coating TiC layer and the cemented carbide base material, which also causes significant damage to the coating. Inhibits the wear resistance of the chip. Therefore, the inventor considered the following in order to solve both the above-described problems of the occurrence of the η phase and peeling of the coating layer.

In order to prevent peeling of the coating layer and to prevent the generation of η phase while maintaining sufficient carbon supply through diffusion from the cemented carbide base material,
It was considered that carbon could be accumulated in the form of free carbon in the cemented carbide matrix prior to coating with TLC by chemical vapor deposition.

It is generally known that the presence of free carbon in cemented carbide significantly impairs wear resistance, but in the case of the present invention, wear resistance largely depends on the surface coating layer, so free carbon is reduced. It was thought that the wear resistance would not decrease much even if a cemented carbide base material containing the above-mentioned properties was used. When a cemented carbide base material containing free carbon was coated with titanium carbide by chemical vapor deposition in accordance with the above idea, no η phase was present at all.

Moreover, it has become possible to create a coating chip in which peeling of the coating layer hardly occurs during cutting. Furthermore, it has been found that free carbon in the cemented carbide base material, which contributes to the formation of titanium carbide, is limited to about 50 μm from the surface under coating conditions using the normal chemical vapor deposition method, so free carbon will precipitate to a deeper depth. It turns out that it's fine if you do it.

In addition, the limit on the amount of free carbon is 0.01 to 0.50% by weight, but no effect is observed below 0.01% by weight, or 0.01% by weight or less.
．． This is because at 50% by weight, the abrasion resistance after coating is impaired.

Next, a method for manufacturing such a free carbon precipitated cemented carbide will be explained.

The properties of cemented carbide vary greatly depending on the amount of carbon it contains.If the amount of carbon is less than a certain amount, a decarburized phase called η phase will precipitate, resulting in a significant decrease in strength; Even if the carbon content is high, free carbon will precipitate and the strength will decrease, both of which are undesirable.For cemented carbide manufacturers, how to adjust the carbon content of cemented carbide to an appropriate range is a serious problem. Ta.

However, as mentioned above, in the manufacture of surface-coated cemented carbide parts, the weight is 0.01 to 0.50 at a depth of 50 μ or more from the surface. Since it was found that precipitation of free carbon is preferable,
How to supply such a free carbon precipitation alloy will be described below. In order to produce a free carbon precipitated cemented carbide, for example, an excess of the necessary carbon may be blended in advance at the raw material blending stage, and free carbon may be precipitated throughout the alloy.

However, this case has the disadvantage that free carbon remains in the center of the alloy even after coating. This free carbon deteriorates the toughness of the alloy. The present invention provides a method for producing an alloy that does not have this drawback and takes advantage of the advantages of free carbon-containing alloys. The principle of this force method is to prepare a cemented carbide in which free carbon exists only in the surface layer, and to supply this free carbon to the surface layer during surface coating. This will be explained in detail below. It is widely known that if steel is treated in a carburizing atmosphere at high temperatures, carbon will carburize from the surface and the surface will harden. The amount of carbon dissolved in solid solution in the CO metal is extremely small and cannot be said to be sufficient.

Therefore, the inventor thought as follows. Figure 1 shows Raut
The cut plane at 84WC-16C0 in the ternary phase diagram of W-C-CO by ala, NOrtOn,
According to this, at temperatures above the liquid phase appearance temperature (1,3000C), for example at 1,400℃, the boundary between WC+L+C and WC+L is 5.3% in terms of carbon content in the alloy, and when cooled to room temperature, it is 0.15%. It is found that it contains free carbon.

If carbon is milled at a temperature below 1,300°C, for example 1,250°C, it will contain only about 5.15% of carbon, as shown by the dotted line in Figure 1, and if it is cooled to room temperature, the maximum carbon content will be 0.01~
0.02 weight? It can only contain free. Therefore, it has been found that it is possible to contain free carbon up to a certain amount by heating the cemented carbide to a liquid phase appearance temperature of 1,300° C. or higher and exposing it to a carburizing atmosphere. The limit of free carbon content is thought to be controlled by the amount of CO in the tenon cemented carbide, and approximately the amount of CO can be expressed as X weight? Then, it is considered to be expressed as x 1 x 0.15%.

Regarding the temperature, a temperature of 1,500°C or higher is not preferable because the cemented carbide to be treated will be deformed.

Regarding the carburizing atmosphere, the activity of carbon in the atmosphere is expressed as AO.
(assuming that the activity of free carbon under 1 atmosphere is 1), the so-called carbon potential expressed as UO-RTlnaO is 0Kc.
Theoretically, carburization is possible if it is a1/MO1 or more, but industrially it is preferably 4Kca1/Mo1 or more.

It goes without saying that the depth of carburization and the amount of carburization can be adjusted by appropriately adjusting the carbon potential of this carburizing atmosphere, treatment temperature, and treatment time.

This will be explained below using examples.

However, the present invention is not limited to the examples. Example 1 Commercially available ISOP-30 cemented carbide (model number TNMG432E
NU), containing no free carbon, at 1,350'C
Carburizing treatment was performed for 5 minutes in a carburizing atmosphere (the carbon potential of the atmosphere was selected to be 5Kca1/MOle).

When this chip was examined after cooling, it was found that 1.
Uniform weight of 0.08 to a depth of 00μ? Free carbon was precipitated. This chip was placed in an Inconel reaction vessel for 1.
Heat to 000 °C, [1286% TiCl47% CH47
% (volume %) of mixed gas was flowed at 4011 mHg, and a commercially available 1S0P-30 cemented carbide (model number TNMG432ENU) was coated with 5 μm of titanium carbide under exactly the same conditions as the chip of the present invention. A cutting test was conducted under the following conditions. Cutting conditions 1 Work material
S55C forged material (HB-250) Work material dimensions φ50m
m><1300mm Cutting speed 140m/Min Feed 0.40mm/Rev Depth of cut 2~
When cutting at 5 mTL, the chip of the present invention could process 112 chips, whereas the conventional titanium carbide coated chip could only process 65 chips due to peeling of the coating layer.

Cutting conditions 2 Work material SCM2l forged material B-180
) Work material dimensions φ50mmX1300mw! Cutting speed 1
30/Min feed 0.30m7! When cutting with an L/Rev depth of 2 mm, the chip of the present invention had a diameter of 142 mm.
While this process was possible, only 98 chips could be processed using a conventional titanium carbide coated chip.

Example 2 Commercially available ISOP-30 cemented carbide (model number SNU
432) ...Contains no free carbon...
... were carburized under the same conditions as in Example 1, and carbon was already added in the raw material state, and 0.08% by weight.
Chips with free carbon deposits and commercially available ISOP-3
Each of the three cemented carbide chips was coated with 5μ of TiC under the conditions of Example 1.

A cutting test was conducted using each chip as A, B, and C under the following cutting conditions. Cutting conditions 1 Work material SC
M3 (HB-280) Cutting speed 170m/Min feed
0.36 mm/Re, depth of cut 2.0 mm, and when the blank wear was determined to be 0.20 mm, there was no particular difference between the three, A26 minutes, B27 minutes, and C27 minutes.

Cutting conditions 2 Work material SCM34 groove material (HB-280
) Workpiece shape Figure 2 Cutting speed 100m/Min Feed 0.20mm/Rev Depth of cut 4
When testing 10 sections each for 3 minutes cutting time, A chip had 8 sections, B
Similarly, the tip C was able to cut 8 sections, but the tip C could only cut 4 sections.

[Brief explanation of drawings]

Figure 1 shows 84WC-1 in the W-CO-C ternary phase diagram.
It is a 6C0 cross section.

Claims (1)

[Claims] 1. When manufacturing surface-coated cemented carbide parts coated with one or more layers of carbides, nitrides, and/or solid solutions or mixtures thereof, the cemented carbide parts before surface coating are Heating in a carburizing atmosphere at a temperature higher than the liquid phase appearance temperature, preferably 1,325°C or higher and 1,500°C or lower, and the carburizing atmosphere has a carbon potential of 4 Kcal/mol or higher,
After that, free carbon is precipitated mainly on the surface of the cemented carbide by cooling the carbon potential to 0 Kcal/mol or more, and then part or all of the free carbon is coated on the surface by chemical vapor deposition. A method for producing a surface-coated cemented carbide component, comprising supplying a coating film to be formed.