JPH04221057A - Formation of wear resistant hard coating film - Google Patents

Abstract

PURPOSE:To efficiently form a coating film having superior wear resistance and adhesion. CONSTITUTION:A wear resistant coating film of 0.8-10mum thickness having a chemical compsn. represented by a formula (VxTi1-x)(NyC1-y) (where 0.25<=x<=0.75 and 0.6<=y<=1) is formed on the surface of a substrate by arc discharge with a cathode as an evaporating source in vacuum of 1X10<-3>-5X10<-2>Torr.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a hard wear-resistant coating, and more particularly to a method for efficiently forming a wear-resistant coating with excellent adhesion.

0002

[Prior Art] When manufacturing high-speed tool steel, cemented carbide tool steel, etc., nitriding such as Ti is applied to the surface of the tool base material in order to improve performance such as wear resistance. Formation of a wear-resistant film made of carbide or carbide has been carried out.

CVD (chemical vapor deposition) and PVD (physical vapor deposition) are conventionally known methods for forming the above-mentioned wear-resistant coating. However, the former method exposes the base material to high-temperature treatment, which may cause deterioration of the base material properties, so the latter method is preferred for tools where base material properties are also important. Ti by ion plating method that can be coated under low temperature conditions
Formation of N film etc. is commonly used.

The TiN film has better heat resistance than the TiC film, and exhibits the function of suppressing crater wear on the rake face of the tool due to machining heat and frictional heat during cutting. However, TiN film has lower hardness than TiC film, so it is vulnerable to flank wear that occurs on the flank surface that contacts the workpiece, and TiN film is more susceptible to flank wear than TiC film.
Films exhibit higher durability.

[0005] Therefore, as a film with excellent heat resistance and hardness, P coatings using ion plating method, sputtering method, etc.
TiAlN, TiAlC, or TiAlC by VD method
A film of N, etc. (hereinafter sometimes referred to as TiAlN, etc.) has been proposed [Japanese Patent Application Laid-Open No. 62-56565, Journal
Vacuum Society Technology (J. Vac
．． Sci. Technol. ) Volume A 4(6), 19
1986, p. 2717, J. of Solid St
ate Chemistry, 70, 1987, pp. 318-322].

By the way, the above-mentioned PVD method is a coating method that utilizes the energy of ions, and since the deposition is carried out at a low temperature, it does not cause the deterioration of the base material properties as seen in the CVD method, but Since no thermal diffusion layer is formed between the film and the film, PVD coating films are generally inferior to CVD coating films in terms of adhesion.

[0007] Furthermore, the film itself such as TiAlN is also TiN.
Since the adhesion is lower than that of TiAlN, the original functions of the TiAlN film, such as wear resistance and high hardness, are not fully exhibited.

As the ion plating method, for example, there is a technique disclosed in Japanese Patent Publication Nos. 59-18474 and 18475, in which the ionization of the metal element component is mainly performed by the discharge of the metal element vapor itself. and set the partial pressure of the reaction gas to 1 x 10-4 to 9 x 10-4.
A method has been proposed in which a coated steel or coated cemented carbide with high adhesion is obtained by applying a high degree of vacuum to 4 Torr.

However, since the above technology is based on a high degree of vacuum, the amount of nitrogen gas introduced is also limited.
This has the problem that the reaction rate and film formation rate become slow and, conversely, the film composition lacks stability in terms of uniformity.

0010

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a film forming method that can efficiently form a film with excellent wear resistance and adhesion. It is something to do.

[0011]

[Means for Solving the Problems] The present invention, which achieves the above object, is a method for forming an abrasion-resistant film on the surface of a base material, which has a chemical composition as shown below, and has a film thickness of 0.8 to 10 μm.
Abrasion resistant coating of 1 x 10-3 to 5 x 10-2 Torr
The gist of this method is to form the film under vacuum conditions using an arc discharge method using a cathode as an evaporation source.

0012

[Operation] The method of the present invention ionizes metal components by arc discharge using a cathode as an evaporation source, and can be carried out by a PVD method such as an ion plating method or a sputtering method. Among the above-mentioned PVD methods, the case where the ion plating method is used will be described below as a representative example. As mentioned above, the metal components ionized by arc discharge using the cathode as the evaporation source,
The reaction is carried out in a N2 atmosphere or a N2/CH4 atmosphere. Although V and Ti may be used individually as the cathode, VxTi1-x having the same composition as the target composition
It is preferable to target the film composition because it is easy to control the film composition for the following reasons. That is, in the method of the present invention, each alloy component is evaporated in a large current range of several tens of amperes or more, so that almost no compositional deviation of the cathode material occurs. Furthermore, a film with even better adhesion can be obtained by increasing the ionization efficiency, increasing the reactivity, applying a bias voltage to the substrate, etc.

[0013] The composition of the above film must be 0.3≦x≦0, preferably 0.3≦x≦0
．． 7, more preferably 0.4≦x≦0.6. Figure 1 shows (VxTi1-x)N[
However, x = 0.2 , 0.4 , 0.6 , 0.8 ] and (Al0.6Ti0.4)N formed to a thickness of 3 μm by ion plating method, the results of measuring the hardness by micro Vickers are shown. It is a graph. From this, in the case of (VxTi1-x)N, 0.4 ≦x≦
It can be seen that in the range of 0.6, a film with higher hardness than the conventional (Al, Ti)N coating can be obtained.

FIG. 2 is a graph showing the results of evaluating the adhesion of the above coating film by a scratch test. In the above scratch test, a spherical diamond indenter with a grain size of 0.2 mm was pressed against the sample surface, and the sample surface was scratched while applying a load at a constant speed. The load at which the film began to peel off was read as the critical load to evaluate the adhesion.

From this, in the case of (VxTi1-x)N, x
It can be seen that when x is in a range of 0.8 or more, adhesion higher than that of the conventional (Al, Ti)N coating cannot be obtained, and that x is preferably in a range of 0.6 or less.

[0016] In order to improve wear resistance by applying a coating to a cutting tool or the like, it is necessary that the coating film has high hardness and good adhesion to the base material. Figure 1,
2, to obtain a film with better hardness and adhesion than the conventional (Al, Ti)N coating (VxTi1-x)
It can be seen that 0.25≦x≦0.75 should be satisfied for N.

[0017] As shown in the Examples and Comparative Examples described later,
If the film thickness is less than 0.8 μm, the abrasion resistance will be insufficient, while if the film thickness exceeds 10 μm, cracks will easily occur and the strength will be insufficient. Therefore, the thickness of the wear-resistant hard coating according to the present invention is limited to 0.8 μm or more and 10 μm or less.

[0018] Furthermore, the gas partial pressure during ion plating was limited to 1 x 10-3 to 5 x 10-2 Torr in order to make the hard coating crystalline and improve the cutting performance as a tool such as wear resistance. It is. If the above gas partial pressure is too low, the film formation rate will be slow and a crystalline hard film will not be obtained.
On the other hand, if it is too high, N in the chemical composition increases and the toughness of the film deteriorates, which is not desirable.

Furthermore, the present invention does not limit the base material on which the film is formed, and may be appropriately selected depending on the application, such as WC-based cemented carbide, cermet, or high-speed steel.

Furthermore, in the present invention, the high hardness of TiC (room temperature hardness Hv: approximately 3200k) is improved by forming carbonitrides.
g/mm2). That is, when the value of y in the composition formula according to the present invention decreases, the hardness increases accordingly and the wear resistance improves. Figure 3 shows that (V0.6T
i0.4) (NyC1-y) [However, y=0.4,0.
6, 0.8, 1] with a thickness of 3 μm, and the work material S5
Cutting speed of 0C (HB: 180-200) 170m/m
in, feed rate 0.25 mm/rev, depth of cut 0.
The results of measuring the amount of crater wear after 15 minutes when cutting with a thickness of 1 mm are shown. As seen in this result, y is 0
．． If it is less than 6, oxidation resistance decreases and crater wear is likely to occur, so y needs to be 0.6 or more.

[0021]

[Example] Example 1 A cemented carbide chip (WC-10% Co as the main component) was attached to a substrate holder of a cathode arc type ion plating apparatus using V0.6Ti0.4 as a cathode electrode. This device was equipped with a base material rotation mechanism and a heater to ensure uniformity in the formation of the wear-resistant film.

During film formation, a bias voltage of -70V was applied to the substrate while maintaining the substrate temperature at 400°C using a heater, and high purity N2 gas was introduced into the apparatus to a temperature of 7 x 10-3 Torr. Then, arc discharge was started to form a film with a thickness of 4 μm on the surface of the base material. The film thickness was measured by breaking one of the base materials attached to the substrate holder at the same time and observing the film cross section with a scanning electron microscope. Furthermore, to quantify the film composition, we analyzed the film depth direction using Auger spectroscopy on the substrates attached at the same time.As a result, there was no change in the concentration of V, Ti, and N in the film thickness direction, and the film was constant. The film composition was identified as (V0.61Ti0.39)N from the peak heights of each component element. The metal component ratio Ti/V in the film has no deviation from the cathode component ratio and can be said to be almost the same.

Example 2 Example 1 except that a V0.5Ti0.5 cathode was used.
Film formation was performed under the same conditions as . The film thickness was 3.5 μm, and the film composition was (V0.5Ti0.5)N.

Example 3 Film formation was carried out under the same conditions as in Example 2 except that N2/CH4 mixed gas was used as the reactive gas. Film thickness is 4.1
μm, and the film composition is (V0.51Ti0.49)(N
0.7C0.3).

(Comparative Example) The following sample was prepared for comparison. Comparative Example 1 A sample in which no film was formed on the substrate of Example 1. Comparative Example 2 N2 gas was heated to 7×10-3 Torr using a Ti cathode.
A TiN film was formed under the same conditions as in Example 1. The film thickness was 4.2 μm. Comparative Example 3 Example 1 except that an Al0.6Ti0.4 cathode was used
Film formation was performed under the same conditions as . The film thickness was 4.3 μm, and the film composition was (V0.61Ti0.39)N. Comparative Example 4 A film was formed in the same manner as in Example 1, except that the film was formed to have a thickness of 0.7 μm. The film composition is (V0.61T
i0.39)N. Comparative Example 5 A film was formed in the same manner as in Example 1 except that the film was formed to have a thickness of 12 μm. The film composition is (V0.6Ti0.
4) It was N.

Table 1 shows the flank wear width and crater wear depth obtained by subjecting the samples obtained in Examples 1 to 3 and Comparative Examples 1 to 5 to a 10 minute cutting test under the following cutting conditions. Cutting conditions: Work material S50C (HB: 180 ~ 2
00) Cutting speed 170m/min Feed rate 0.25 mm/rev Depth of cut
0.1 mm

[0027]

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

Next, an example of application to a carbide drill will be shown below. Example 4 A film was formed on a 6 mmφ carbide drill (WC-8% Co as the main component) under the same conditions as in Example 1. Film thickness is 4
．． 5 μm, and the film composition is (Al0.65Ti0.35
)N.

The following sample was prepared as a comparative example. Comparative Example 6 A TiN film was formed on a 6 mm diameter carbide drill under the same conditions as Comparative Example 2. The film thickness was 4.4 μm. Comparative Example 7 A film was formed on a 6 mm diameter carbide drill under the same conditions as Comparative Example 3. The film thickness is 4.3 μm, and the film composition is (V0
．． 61Ti0.39)N. Comparative Example 8 A film was formed on a 6 mm diameter carbide drill under the same conditions as in Example 4. The film thickness is 0.7 μm, and the film composition is (V0.
6Ti0.4)N. Comparative Example 9 A film was formed on a 6 mm diameter carbide drill under the same conditions as in Example 4. The film thickness is 12 μm, and the film composition is (V0.6
Ti0.4)N.

Table 2 shows the results of the number of holes drilled under the following cutting conditions. Cutting conditions: Work material S50C, 13mmt (through hole machining) Cutting speed 50 m/min feed rate
0.2 mm/rev lubrication
by emulsion

[0031]

[Table 2] As is clear from Table 2, the tool obtained by the method of the present invention showed a significant increase in the number of pieces machined compared to the comparative example, and had good wear resistance.

Next, an example of application to a high speed steel drill will be shown below. Example 5 A film was formed using a 6 mm diameter high speed steel drill under the same conditions as in Example 1. The film thickness is 5.5 μm, and the film composition is (Al0
．． 63Ti0.37)N.

The following sample was prepared as a comparative example. Comparative Example 10 A TiN film was formed on a 6 mm diameter high speed steel drill under the same conditions as Comparative Example 2. The film thickness was 4.2 μm. Comparative Example 11 A film was formed using a 6 mm diameter high speed steel drill under the same conditions as Comparative Example 3. The film thickness was 4.0 μm and the film composition was (Al0.
60Ti0.40)N. Comparative Example 12 Example 1 except that the film was formed so that the film thickness was 0.7 μm.
Film formation was carried out in the same manner. The film composition is (V0.61Ti
0.39)N. Comparative Example 13 A film was formed in the same manner as in Example 1, except that the film was formed to have a thickness of 12 μm. The film composition is (V0.61Ti0.
39) It was N.

Table 3 shows the results of the number of holes drilled under the following cutting conditions. Cutting conditions: Work material S50C, 10mmt Cutting speed 30 m/min Feed rate 0
．． 15 mm/rev Lubricated by emulsion

[0035]

[Table 3] As is clear from Table 3, the tool obtained by the method of the present invention showed a significant increase in the number of pieces machined compared to the comparative example, and had good wear resistance.

[0036]

[Effects of the Invention] Since the present invention is constructed as described above, it is superior in terms of adhesion, uniformity of film composition, and production efficiency compared to the conventional ion plating method or sputtering method. A film forming method can be provided.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between (VxTi1-x)N composition (represented by nitride) and hardness according to the present invention.

FIG. 2 is a graph showing the relationship between (VxTi1-x)N and critical load according to the present invention.

FIG. 3 is a graph showing the amount of crater wear during cutting of a carbide tip when y is changed in (V0.6Ti0.4) (NyC1-y).

Claims (1)

[Claims] Claim 1: In forming an abrasion-resistant film on the surface of a base material, the film has a chemical composition represented by the following, and has a film thickness of 0.8 to 10 μm.
m wear-resistant coating to 1 x 10-3 to 5 x 10-2 Torr
A method for forming a wear-resistant hard coating, characterized in that the coating is formed by an arc discharge method using a cathode as an evaporation source under vacuum conditions of r.