JP2580330B2 - Wear resistant coating - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant coating useful as a surface coating material for a machine tool used for machining such as milling, cutting, and drilling. .

[Prior art] When manufacturing high-speed tool steel or cemented carbide tool steel,
In order to improve the performance such as wear resistance, a wear-resistant film made of nitride or carbide such as Ti is formed on the surface of a tool base material.

As a method of forming a wear-resistant film on the surface of a base material, a CVD method (chemical vapor deposition method) and a PVD method (physical vapor deposition method) are conventionally known. However, in the former method, the base material is exposed to a high-temperature treatment, so that the base material characteristics may be deteriorated. In the case of a tool in which the base material characteristics are also regarded as important, the latter method tends to be preferred.

Therefore, a high-frequency discharge plasma CVD method, a reactive ion plating method, a sputtering method, and the like, which can perform a coating treatment under a relatively low temperature condition, have been adopted.

TiN and TiC by ion plating are widely used as wear-resistant films for tools and the like, and in particular, TiN films having excellent high-temperature oxidation resistance (heat resistance) are widely used. That is, since TiN has better heat resistance than TiC, it has a function of protecting the rake face of a tool, which is heated by machining heat or frictional heat during cutting, from crater wear. However, since TiN has a lower hardness than TiC, it is rather vulnerable to flank wear generated on a flank in contact with a work material, and TiC exhibits higher durability against flank wear.

In recent years, there has been a demand for higher cutting speeds, and cutting conditions have tended to be more severe. Therefore, the above conventional TiN film cannot meet this demand.

Therefore, as a film with even better heat resistance and hardness, TiAlN, TiAl by ion plating method or sputtering method
Coatings such as C, or TiAlCN have been proposed [JP-A-62-56565,
J.Vac.Sci.Technol.A 4 (6), 1986, p.
And J. of Solid State Chemistry, 70, 1987, 318
322 pages].

[Problems to be Solved by the Invention] Since the PVD method is a low-temperature coating method using ion energy, a diffusion layer due to heat as in the CVD method does not exist between the substrate surface and the film. Therefore, a film formed by the PVD method generally has inferior adhesion to a film formed by the CVD method.

On the other hand, recently, from the viewpoint of improving the wear resistance and extending the life, there is a tendency to increase the thickness of the coating, but as the thickness increases, the internal stress of the coating increases, and cracks may occur in the coating. The adhesiveness of the film is reduced, which causes peeling of the film. In addition, (A)
As described above, l, Ti) (N, C) -based coatings have been proposed. However, since these coatings have an internal stress more than twice as high as that of the TiN coating, a TiN coating is formed. It is practically used by forming a film thickness as thin as possible.

In view of the above, there is a demand for an improvement in a film forming technique that can sufficiently exhibit particularly excellent properties such as an (Al, Ti) (N, C) film.

The present invention has been made in view of such circumstances, and it is possible to form a film under relatively low temperature conditions, and nevertheless, has excellent adhesion and film strength, and has a resistance to crater wear and flank wear. It is an object of the present invention to provide an abrasion-resistant film excellent in the above.

[Means for Solving the Problems] The present invention which has achieved the above object is TiC _X N _1-X (where 0
≦ X ≦ 0.6), and the layer thickness is 0.3 to
A 6 μm coating layer is formed on the substrate surface, and (Al _y T
i _1-y ) (N _z C _1-z ) (however, 0.05 ≦ y ≦ 0.75, 0.6 ≦ z ≦ 1)
This is a wear-resistant coating having a chemical composition represented by the formula (1) and having a thickness of 0.6 to 8 μm formed on the uppermost layer and having at least two layers.

[Operation] The present invention is configured as described above. In short, TiC _X N _1-X
By forming a coating layer having a chemical composition represented by the formula (0 ≦ X ≦ 0.6) on the substrate surface, adhesion to the substrate surface is achieved and (Al _y Ti _1-y ) (N _z C _1-z ) (however,
By forming a film layer having a chemical composition represented by 0.05 ≦ y ≦ 0.75, 0.6 ≦ z ≦ 1) on the uppermost layer, it was found that an abrasion-resistant film excellent in film strength could be realized.
The present invention has been completed. In the film of the present invention, the above 2)
It is preferable that an intermediate layer having a chemical composition in which the components constituting the respective coating layer compositions are mixed or a chemical composition continuously changing over the two coating layer compositions is interposed between the two coating layers. By interposing a layer, the effect of the present invention becomes more remarkable.

In forming each of the above-mentioned coating layers, a method of ionizing a metal component by arc discharge using a cathode as an evaporation source, that is, a PVD method represented by an ion plating method, a sputtering method, or the like can be performed.
Of these methods, for example, the case where the ion plating method is used will be described as a representative example.

In this method, the metal component ionized as described above is reacted in an N ₂ atmosphere or an N ₂ / CH ₄ atmosphere to coat a nitride or a nitrocarbide. For the cathode, Ti (C, N)
For the purpose of forming a system film, Ti may be used,
On the other hand, when the purpose is to form a (Al, Ti) (C, N) coating,
Ti and Al can be used individually, but if targeting Al _X Ti _1-X consisting of the target composition itself,
Easy control of film composition.

Since the evaporation of each alloy component is performed in a large current range of several tens of amperes or more, there is almost no composition deviation of the cathode material. In addition, a film having high ionization efficiency and high reactivity and having excellent adhesion can be obtained by applying a bias voltage to the substrate.

The amount of solid solution of C in the formed film can be determined by X-ray analysis, Auger analysis, or the like, and more accurate composition control can be performed by knowing the correlation between the analysis value and the CH ₄ flow rate.

In the present invention, the composition of the coating layer formed on the substrate surface (hereinafter, sometimes referred to as the first coating layer) must be TiC _X N _1-X (where 0 ≦ X ≦ 0.6). . The reason why the chemical composition of the first coating layer is limited as described above is that adhesion to the substrate surface is considered. The first coating layer is (Al, Ti)
The effect of the present invention can be achieved even with TiN (when x = 0) having an internal stress lower than that of the (N, C) film, but Ti (C, N) is required to exhibit higher wear resistance. It is desirable to use a system coating (when x ≠ 0). The reason is as follows.

TiC has a high normal temperature hardness (Hv) of 3100 kg / mm ² , but has the disadvantage of lacking heat resistance and being easily oxidized, while TiN has excellent oxidation resistance at high temperatures and good adhesion even at relatively low temperatures. The coating layer can be easily formed, but Hv is 20
00kg / mm ² or less and there is a slightly lower difficulties.

In contrast, TiN of the chemical composition represented by the general formula TiC _X N _1-X
-In the TiC solid solution system coating layer, by appropriately adjusting the amount of solid solution C (x), it is possible to obtain the high hardness of TiC while having the characteristics of TiN with good adhesion and excellent oxidation resistance. it can. That is, the first coating layer has the characteristics of TiN and
As the amount of solid solution increases (as x increases), the hardness increases, and excellent performance is exhibited also in terms of flank wear resistance. As x increases, the film layer becomes harder, flank wear is eliminated, and the color tone of the film starts to change from gold to reddish, and further changes from red to gold with an increase in the amount of C. As for the oxidation resistance, the performance satisfying this is maintained. On the other hand, if x exceeds 0.6, adhesion and oxidation resistance deteriorate, and a minute film peels off at the edge of a tool member or the like, and crater wear easily occurs. Further, the film formation rate decreases with an increase in the amount of solid solution of C, and decreases remarkably in a region where x exceeds 0.6. For the above reason, the range of x is set to 0 to 0.6 in the present invention.

Note that the thickness of the first coating layer needs to be 0.3 to 6 μm. When the layer thickness is less than 0.3 μm, the internal stress of the film layer formed on the uppermost layer cannot be appropriately reduced, while when the layer thickness exceeds 6 μm, the strength of the film itself decreases.

Next, the chemical composition of the coating layer formed on the uppermost layer (hereinafter sometimes referred to as a surface layer) is (Al _y Ti _1-y ) (N _z C _1-z ) where 0.05 ≦ y ≦ 0.75 0.6 ≦ z ≤ 1 and preferably 0.6 ≤ y ≤ 0.7.

The solid solution composed of the above surface layer composition will be described using a nitride system as a representative. This solid solution is a solid solution having AlN-TiN as an end composition, and as a result of examining various component ranges,
As shown in Fig. 1, the internal stress (compressive stress) is 1.9x that of TiN.
(Al _y Ti _1-y ) N (y is 0.05 or more) compared to 10 ¹⁰ dyne / cm ²
It can be seen that the average shows a value of 4.7 × 10 ¹⁰ dyne / cm ² up to y = 0.6. As the AlN component further increases, the internal stress decreases accordingly, and at y = 0.7, the crystal structure becomes NaC
The internal stress is changed from 2.8 (Bl structure) to ZnS (Wurzite type) to 2.8 × 10 ¹⁰ dyne / cm ² .

FIG. 2 is a graph showing a change in hardness when y is changed in the (Al _y Ti _1-y ) N coating layer.

As is clear from FIG. ² , the hardness increases from Hv ≒ 2000 kg / mm ^{2 of} TiN as y increases from 0, and shows a maximum value of HvN3000 kg / mm ² when y is 0.6. Shows a decrease in hardness accompanying a change in the crystal structure as the value increases from 0.6. When y becomes 0.75, the hardness becomes almost equal to the hardness of TiN, and when y exceeds 0.75, the hardness becomes lower than the hardness of TiN. That is, when the AlN solid solubility (y) exceeds 0.75, the composition of the coating layer becomes close to that of AlN, resulting in softening of the coating layer, insufficient hardness being obtained, and flank wear easily occurring. .

From the above results, in the present invention, considering both the wear resistance and the internal stress, the value of y (AlN solid solubility) is 0.05 to
0.75. The more preferable range of y is 0.6 to 0.7.

In the present invention, TiC is formed by forming carbonitride.
High hardness (normal temperature hardness Hv: about 3100 kg / mm ² ). That is, as the value of z in the composition formula of the present invention decreases, the hardness increases and the wear resistance improves.

Fig. 3 shows carbide tips (mainly composed of WC-10% Co)
(Al _0.65 Ti _0.35 ) to (N _z C _1-z ) [where z = 0.4, 0.6, 0.
8,0.9,1] with a coating speed of 170m /
min, feed rate 0.25mm / rev, cutting depth 0.1mm
The result of measuring the amount of crater wear after 15 minutes is shown.

As can be seen from these results, when z is less than 0.6, the oxidation resistance is reduced and crater wear is liable to occur. z ≧ 0.
In the range of 6, no remarkable decrease in oxidation resistance is observed. Therefore, in the present invention, the range of z is determined to be 0.6 to 1.0.

In addition, as will be clarified in an example described later, the thickness of the surface layer is
When the thickness is less than 0.6 μm, only the effect of the first coating layer is the main effect, and the abrasion resistance becomes insufficient. On the other hand, when it exceeds 8 μm, cracks easily occur in the film itself, and the strength becomes insufficient. Therefore, in the present invention, the thickness of the surface layer is 0.6 to 8 μm.
It was decided.

In the present invention, it is preferable that an intermediate layer having a mixture of the components of the two coating layers or an inclined composition is interposed between the first coating layer and the surface layer. This intermediate layer is provided with a Ti cathode for forming the first coating layer and an Al _y Ti _1-y cathode for forming the surface layer in a vacuum chamber, and simultaneously or in the N ₂ or N ₂ / CH ₄ atmosphere. It can be formed by causing arc discharge while controlling. By interposing such an intermediate layer between the first coating layer and the surface layer, it is possible to realize a wear-resistant coating having excellent adhesion to the substrate while relaxing internal stress of the surface layer. In addition, by adopting such a configuration, the total thickness can be increased as compared with forming a (Al _y Ti _1-y ) (N _z C _1-z ) single film, and heat resistance and abrasion resistance can be improved. A film with better properties is obtained.

As will be apparent from the examples described later, the effect of stress relaxation is recognized when the thickness of the intermediate layer is about 0.2 μm, and 0.5 μm at the maximum is sufficient.

Hereinafter, embodiments will be described. However, the present invention is not limited to the following embodiments, and appropriate design changes in the spirit of the above and below are included in the technical scope of the present invention.

[Example] Example 1 Using a Ti cathode electrode and a cathode electrode having the composition of Al _y Ti _1-y (y = 0.05 to 0.75), a cemented carbide chip (WC) was mounted on a substrate holder of a cathode arc type ion plating apparatus. -10% Co as a main component). The apparatus was provided with a substrate rotating mechanism and a heater for ensuring uniformity of the state of formation of the abrasion-resistant film.

During film formation, the substrate temperature was set to 450 ° C with a heater.
While maintaining the heating, a bias voltage of -70 V is applied to the substrate, high-purity N ₂ gas is introduced into the apparatus to 5 × 10 ^-2 Torr, an arc discharge is started, and Ti ( C
_x N _1-x ) -based coating layer (first coating layer), intermediate layer and (Al _y Ti
_1-y ) ( _{NzC1 -z} ) -based film layers (surface layers) were laminated in this order to form films.

In the measurement of the layer thickness, one of the substrates simultaneously attached to the substrate holder was broken, and the layer cross section was observed and measured with a scanning electron microscope. Further, for the quantitative determination of the layer composition, the base material attached at the same time was analyzed in the layer depth direction by Auger spectroscopy. As a result, there was no change in concentration in the thickness direction of the first coating layer and the surface layer, and the density was constant. An example of the analysis result is as shown in FIG. The metal component ratio Ti / Al in the film was almost the same without any deviation from the cathode component ratio.

For each of the obtained coatings, the flank wear width when subjected to a cutting test for 25 minutes under the following cutting conditions was measured.

Cutting conditions: Work material S50C Cutting speed 170, 200m / min Feed rate 0.25mm / rev Cutting depth 0.1mm The results are shown in Table 1 together with the composition and thickness of each layer. For comparison, Table 1 shows the results when a (Al, Ti) (C, N) -based monolayer film was formed in the same manner as in Example 1 (Nos. 8 to 10), and The composition, the layer film and the flank wear width of the first coating layer out of the range of the present invention (No. 11) were also shown.

As is clear from Table 1, all of the examples of the present invention were superior to the comparative examples in abrasion resistance.

 Next, an example of application to a carbide drill will be described below.

Example 2 Various coatings were formed on a 6 mmφ carbide drill (having WC-9.5% Co as a main component) in the same manner as in Example 1.

The obtained coatings were cut under the following conditions.

Cutting conditions: Work material S50C, 13mm ^t (BH230-250) Cutting speed 80m / min Feeding speed 0.2mm / rev Lubrication Emulsion The results are shown in Table 2.

As is evident from Table 2, the tool obtained by the method of the present invention has a remarkably increased number of processed parts as compared with the comparative example.
The wear resistance was good.

 Next, an example of application to a high speed drill is shown below.

Example 3 Various films were formed on a 6 mmφ high-speed drill in the same manner as in Example 1.

The obtained coatings were cut under the following conditions.

Cutting conditions: Work material S50C, 10mm ^t Cutting speed 30m / min Feeding speed 0.18mm / rev Lubrication Emulsion The results of the number of perforations are shown in Table 3 together with the composition and thickness of each coating layer.

As is evident from Table 3, the tool obtained by the method of the present invention showed a remarkable increase in the number of processed parts as compared with the comparative example, and had good wear resistance.

Since the present invention is constituted as described above [Effect of the invention], TiN basic and the Ti (C, N) -based film which has originally good adhesion to a substrate, the surface layer is, III _b Since it is a film layer in which Ti is dissolved in AlN, which is a group III nitride, heat resistance, thermal conductivity, etc.
Excellent characteristics similar to AlN are exhibited.

[Brief description of the drawings]

Figure 1 is a graph showing a change in the internal stress in the case of changing the y in _{(Al y Ti 1-y)} N -based coating layer, FIG. 2 (Al _y T
i _1-y ) A graph showing the change in hardness when y is changed in the N-based coating layer. FIG. 3 shows (Al _0.65 Ti _0.35 ) (N
FIG. 4 is a graph showing the amount of crater wear during cutting of a hardness tip when z is changed in a _z C _1-z ) -based coating. FIGS. FIG.

Claims (2)

(57) [Claims] 1. A consists chemical composition represented by TiC _X N _1-X (where 0 ≦ X ≦ 0.6), with coating layer of thickness is 0.3~6μm is formed on the substrate surface, (Al _y Ti _1-y ) (N _z C _1-z ) (However, 0.05 ≦ y ≦ 0.75, 0.6 ≦ z
≦ 1) A wear-resistant coating comprising a chemical layer having a chemical composition represented by the following formula and having a layer thickness of 0.6 to 8 μm formed on the uppermost layer and comprising at least two layers. 2. A method according to claim 1, wherein a chemical composition obtained by mixing the respective coating layer compositions or an intermediate layer continuously changed over the two coating layer compositions is interposed between the two coating layers. The abrasion-resistant film described in (1).