JPS62246429A - Manufacture of tough ceramic tool - Google Patents

Abstract

PURPOSE:To enhance the wear-resistance and toughness of a ceramic tool, by holding a sintered ceramic mother material at a temperature of 1,150-1,500 deg.C, and by covering the outer surface of the mother material with a thin Al2O3 film having a thickness of 0.5-20mum with the use of a chemical gas phase vapor deposition. CONSTITUTION:If a covering layer is formed at a temperature below 1,150 deg.C, it may not ensure a sufficient useful life for an Al2O3 covering film, but if it is formed at a temperature about 1,500 deg.C, the particle size of Al2O3 particles is greater than about 5mum so that the wear-resistance of the covering film is deteriorated and therefore is unpreferably. Accordingly, a sintered ceramic mother material is held at a temperature of 1,150-1,500 deg.C. Further, if a thin Al2O3 film layer has a thickness of less than 0.5mum, the effect of improvement in the wear-resistance may not be expected, and if the thickness of the film layer is greater than about 20mum, it is economically unpreferable since the effect due to covering by the Al2O3 film layer is saturated. Accordingly, the outer surface of the sintered ceramic mother material is covered with a thin Al2O3 film having a thickness of 0.5-20mum with the use of a gas phase vapor deposition process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing strong ceramic tools. More specifically, the present invention relates to a method for manufacturing a ceramic cutting tool that is composed of a ceramic sintered base material and a thin film layer coated thereon, and has extremely high wear resistance and toughness.

BACKGROUND OF THE INVENTION In recent years, due to the depletion of tungsten resources as a carbide tool material, the development of alternative carbide tool materials has been actively conducted. As such a new material, cemented carbide has attracted attention as a cutting tool material because of its excellent wear resistance, corrosion resistance, heat resistance, etc., and WC-Co, WC-(WTiT
aNb), a C-Co based WC-based cemented carbide tool was developed. In addition to this, we also offer TiC-Ni-Mo based cermet tools, pure^1□03 or A1□03+TI
C-based ceramic tools and sintered diamond tools have been developed and put into practical use.

Among these tools, ceramic tools have high hardness at room temperature and high temperature, and the cutting edge is oxidized at high temperatures, so it is possible to avoid welding of chips. Therefore, it is possible to cut at high speed, and the workpiece (workpiece It has various advantages such as a wide range of applications (materials) and ease of handling. However, on the other hand, a particular problem compared to tools made of cemented carbide is that they are inferior in terms of transverse rupture strength, that is, toughness. Therefore, various methods have been proposed to solve this problem of transverse rupture force.

For example, as seen in the invention disclosed in Japanese Patent Publication No. 53-13276, hard carbides and/or hard nitrides, such as Ti and Zr5, are added to the A1□o3 sintered body or Al2O3.
Hf.

Ceramic tools are known in which the base material is a sintered body obtained by adding carbides and/or nitrides such as B, and the surface thereof is coated with an Al2O3 film.

In addition, the invention disclosed in Japanese Patent Publication No. 59-13475 is Si3N,
as the main component, and MgO1Y203 and Ta as sintering aids.
205, ZrO□, A1□0. Al was added to the surface of the sintered body by chemical vapor deposition (CVD).
A method for manufacturing a ceramic indexable chip with a thin coating of 2O3 and/or AlON is disclosed.

Furthermore, the invention disclosed in JP-A-60-127905 includes A14.
A ceramic tool has been proposed in which a thin Alzos coating film is formed on the surface of a sintered body containing 0s as a main component and hot added as a sintering aid.

However, coated ceramic tools composed of a ceramic sintered base material and a vapor-deposited film of Al2O3 as described above still have significantly inferior toughness, especially thermal shock resistance and thermal fatigue toughness, and therefore have poor wear resistance. Despite its excellent properties, its field of application was extremely limited.

Therefore, in order to improve these characteristics, we created an Al2O3 coating thin film using TiC, TiN5Ti (C
Strong ceramic tools have been developed whose toughness has been improved by adding elements such as O), VJC, 7, and rO□. However, although it is certainly possible to improve toughness by adding the above additives, wear resistance is sacrificed,
The deterioration could not be ignored.

Also, as a result of recent material development, ^120. Instead, ceramic tools containing 5isN< as a main component have been proposed. This Si3N, based ceramic is Al2O
Since it is extremely superior in terms of thermal shock resistance and thermal fatigue toughness compared to Type 3 ceramics, it can be said to be a ceramic material that is extremely superior to conventional ceramic materials. However, when 5i3Na ceramic materials with such excellent properties are considered as materials for cutting tools, they react with iron as the workpiece material, so it is difficult to use 5i3Na-based ceramic materials, which pose a problem of diffusion of chips to the tool surface. It cannot be used for cutting at all, and can only be used for cutting cast metals where diffusion of chips onto the tool surface is not a problem. By the way, the most important point in cutting castings is hardness at high temperatures.
Since Si3N is inferior to Al2O3 in this respect, it is certainly much superior in terms of toughness compared to Al2O*/TiC sintered cutting tools, which have traditionally been widely used in cutting castings. , which was incomparable in terms of wear resistance.

As mentioned above, ceramic tools whose main component is 513N4 are improved in terms of toughness compared to Al2O3 sintered cutting tools (compared with In order to improve this point, in the conventional technology, this ceramic sintered body with excellent toughness is used as a base material, and the surface is coated several μm thick.
A coated ceramic tool coated with an A1□03 thin film having a thickness of .

Problems to be Solved by the Invention The characteristics particularly required of ceramic tools as cutting tools such as cutting tools are transverse rupture strength, that is, toughness and wear resistance.

As mentioned above, A I 203 series tools have excellent wear resistance but are insufficient in terms of toughness, and various solutions have been proposed, but all are unsatisfactory; for example, Si3N,
Although the toughness was improved like that of the AlaOs-based tool, the wear resistance was sacrificed and it became significantly inferior to the AlaOs-based tool. Under these circumstances, a coated ceramic tool has been proposed in which the base material is a Si3N4 ceramic sintered body, which is advantageous in terms of toughness, and the surface thereof is provided with an Al2O3 thin film, which is advantageous in terms of wear resistance.

In this way, by coating the base material (high toughness) of a ceramic tool with an Al2O3 thin film having good wear resistance, the low wear resistance of the base material is compensated for. In fact, for example, about 1% of Al2O3 is added to the surface of a 313N4-based sintered body.
A μm-coated ceramic tool can provide a tool that has both the toughness and wear resistance required of a ceramic tool, and is widely used in the field of casting cutting.

However, since the wear-resistant ^1□0° coating on this cutting tool is extremely thin at approximately 1 μm, it has the disadvantage that when flank wear progresses beyond a certain point, the Al2O3 coating effect is significantly reduced. .

Therefore, it is important to solve the various drawbacks of conventional ceramic tools and develop ceramic tools that are strong and wear resistant, making full use of the characteristics of ceramic tools to cut steel, cast iron, etc. It is extremely important in carrying out processing, and is also an important issue in this industry. An object of the present invention is to provide a method for manufacturing such a ceramic tool, and another object of the present invention is to provide a ceramic tool that is strong, highly wear resistant, and has a long service life.

Means for Solving the Problems In view of the above-mentioned current state of ceramic tools, the inventors conducted various studies and research to develop ceramic tools that are superior in both toughness and wear resistance. In order to maintain the toughness of the sintered compact base material, ensure wear resistance, and improve its service life, it is necessary to increase the adhesion strength between the base material and the thin film coating layer to achieve the desired excellent properties. Based on the idea that a ceramic tool could be realized, the inventors discovered that this improvement in adhesion strength could be achieved by sufficiently controlling the coating treatment temperature, and completed the present invention.

That is, in the method for manufacturing a strong ceramic tool of the present invention, a ceramic sintered body base material is heated and maintained at a temperature within the range of 1150 to 1500°C, and the surface of the base material is coated to a thickness of 0.5 mm by chemical vapor deposition. It is characterized by being coated with an Al2O3 thin film of 5 to 20 μm.

In particular, ceramic sintered base materials useful in the method of the present invention include those containing A1□03 as a main component and 51
Examples include those containing 3N4 as the main component, and the former further contains 5 to
TiC, TiN, Ti(CO) in a proportion of 50% by weight
, WC, and ZrO2, and the latter similarly contains 5
Zr0z, TiN, Y2O3, in a proportion of ~50% by weight
It may contain at least one component selected from the group consisting of Al2O3 and AlN. If the above additive is used in an amount less than 5% by weight, the toughness will be insufficient, and if it is used in an amount exceeding 50% by weight, the wear resistance will be insufficient, and both are preferable. do not have. In the present invention, in addition to the above-mentioned examples, it goes without saying that any Al2O3 sintered body with improved toughness can be used as the base material.

In the method of the present invention, the temperature at which the thin film coating layer is formed is extremely important, as described above, and becomes a critical condition. If the coating layer is formed at a temperature lower than the lower limit of 1150°C, sufficient service life of the Al2O3 coating, that is, sufficient adhesion strength cannot be ensured;
If the thin film is formed at a temperature exceeding 00°C, the Al2O3 particles in the coating layer will have a huge diameter of 5 μm or more, which is undesirable because the wear resistance will deteriorate.

In addition, the strong ceramic tool of the present invention has G)
The thickness of the 03 thin film coating layer is also critical, and is preferably within the above range. That is, if the thickness is less than the lower limit of 0.5 μm, the effect of improving wear resistance by AbOs coating cannot be expected. On the other hand, the upper limit of 20 μm is not so important, and even if it is applied at a thickness greater than this, the effect of the A1°03 coating will be saturated, so it is advantageous to keep the thickness below 20 μm from the economic and industrial production standpoints.

The ceramic sintered body base material used in the method of the present invention can be easily produced by mixing predetermined ingredients in accordance with a conventional method, molding it into a predetermined shape, then firing it, and performing processing such as dimensional adjustment if necessary. can do.

Next, an Al2O3 thin film coating is applied to the surface of the ceramic base material, and any of the physical vapor deposition methods such as various CVD methods and ion blasting methods can be used for this. Here, compared to deposited films obtained by physical vapor deposition, films obtained by CVD, which are coated at the same temperature, are generally considered to have inferior adhesion strength to the base material, but according to the method of the present invention, By carrying out the coating treatment under temperature conditions in the above range, sufficient strength and growth rate can be achieved by conventional chemical vapor deposition methods. Furthermore, this CVD method has excellent coverage and is therefore advantageous for coating base materials with complex shapes.

Function As mentioned above, the most important point in putting ceramic tools into practical use is to have a structure that has both high toughness and wear resistance, and for this purpose, extensive research has been carried out. Among them, CV has an advantageous ceramic base material with high toughness and wear resistance, which is said to be the most improved.
Even with ceramic tools formed by the D method or the like with a thin film of Al20i, Al0N, etc., if flank wear progresses beyond a certain level, the coating effect decreases and sufficient wear resistance cannot be maintained.

Therefore, the present inventors conducted the following cutting test, obtained a wear curve at that time, investigated the relationship between cutting time and flank wear, and plotted the results in the attached FIG. 1. In this cutting test, cast iron (FC25) was used as the work material.
The shape of the cutting tool was model number SNGN120408 and holder F NIIR-44A, and the cutting was carried out under the following conditions without using a cutting agent.

Cutting speed (V) = 500m/min feed rate (f
) = 0.36 mm/Rotary depth of cut (d) = 2 mm In Figure 1, curve (a) is the result of using a ceramic sintered tool whose main component is Si3N<, and curve (b)
) is Al2O applied to the tool used in (a) using the CVD method.

Curve (C) is the result obtained from a tool coated with Al2O3/Tic ceramic sintered body to a thickness of 1 μm. From these results, when compared with the results of a tool made mainly of 513N4 (curve (a)), the results obtained using a conventional ceramic tool (curve (a)) show a significant improvement in terms of wear resistance, but the cutting time is 2
If the flank wear is 0.3 mm or more for 5 minutes or more, A.
It can be seen that the wear resistance improving effect of lzO3 coating is lost.

In order to improve such a short service life, A1□0
3. It is possible to increase the thickness of the coating film. Therefore, the dependence of flank wear on the thickness of the Al2O3 coating was investigated by varying the thickness of the Al2O3 coating. A sintered body containing 313N4 as the main component was used as the base material, and the resulting product was subjected to a cutting test under the same conditions as shown in Figure 1, and the time required for flank wear to reach 0.3+mm was measured.
This is plotted in the attached Figure 2 against the A1□03 film thickness. This result shows that the wear resistance increases as the film thickness increases until the A1□03 film thickness reaches 1 μm, but when the film thickness exceeds 1 μm, the wear resistance rapidly decreases. There is.

This is thought to be because if the film thickness exceeds 1 μm, the coating will peel off during cutting, and if the film thickness exceeds 3 μm, the peeling will actually create a notch effect, making it more It is thought that the wear will also increase. It is a well-known fact to those skilled in the art that when the film thickness increases, the coating film and the base material are more likely to peel off as a result of the difference in rigidity between the coating film and the base material.

Under these circumstances, the inventors of the present invention deeply considered and studied the above test results, and found that in order to solve the problems presented by the conventional method, it is necessary to improve the adhesion strength between the base material and the coating film. I learned that it is advantageous.

Although various methods can be considered to improve the adhesion strength between the base material and the coating film, it is most effective to set the treatment temperature during coating treatment within a specific range as in the method of the present invention. .

Therefore, first, the adhesion strength between the base material and the coating film of coated ceramic tools produced according to various coating methods was measured using a Raytest/Automatic manufactured by Swiss Watch Institute. The principle of this measurement is to scratch the coating film with a loaded diamond cone, detect the load required to destroy the film using ultrasonic absorption measurement, and measure this load [critical load: L].
The adhesion strength is evaluated based on the magnitude of c (referred to as critical load). As a sample, a tool was used in which a sintered base material mainly composed of 5iiN* was coated with a 1 μm thick Al2O3 thin film by CVD, ion blating, and plasma CVD under various temperature conditions. The results are shown in attached Figure 3.
These results show that the adhesion strength is determined almost solely by the coating temperature, regardless of the type of coating method, and the higher the coating temperature, the higher the adhesion strength.

By the way, the upper limit of this coating treatment temperature in the conventional manufacturing method of ceramic tools has been limited to about 1000°C. This is because this type of coated tool manufacturing technology was originally developed from coated cemented carbide, and the base material was generally made of cemented carbide, so when held at a high temperature of 1000°C or higher, the fluidity of the bonded RCO increases. becomes large, and the amount of Co that diffuses into the coating film during the coating operation cannot be ignored, and because of this Co diffusion, no improvement in wear resistance can be expected at all. Therefore, the upper limit of the coating treatment temperature was set at about 1000° C., and it is thought that this was applied as is to ceramic sintered bodies.

Therefore, in the method of the present invention, in order to solve the problem of Co fluidization and diffusion observed in coated cemented carbide tools as described above, the method does not contain components that fluidize at such high temperatures, or it contains very few components that fluidize at high temperatures. A ceramic sintered body containing only a small amount was selected as the base material. This further indicates that, as in the method of the present invention, the coating process can be carried out at higher temperatures than in conventional methods.
This makes it possible to implement the method without the problems described above.

Thus, according to the method of the present invention, as a comprehensive result of setting the coating treatment temperature within a specific range, limiting the coating film thickness, and selecting the composition of the ceramic sintered body base material as described above, , it is possible to realize a ceramic tool that is satisfactory in terms of both toughness and wear resistance and is sufficiently durable for practical use. In this sense, all of the above three requirements are critical for the method of the present invention, and the desired effect can be achieved by implementing the method of the present invention under conditions within a predetermined range.

Furthermore, according to the method of the present invention, by following the above conditions, the range of selection of coating treatment methods is expanded, and a product with sufficient strength can be obtained even with the CVD method, which is generally not expected to provide high adhesion strength.

This CVD method is economical and advantageous in terms of industrial production compared to other physical coating methods, so the ability to utilize the CVD method makes the method of the present invention preferable in terms of productivity.

EXAMPLES The following examples will further specifically explain the method of the present invention and demonstrate the effects of the method of the present invention, but the scope of the present invention is not limited in any way by the following examples.

Example 1 A ceramic sintered body (model number: S
N G N 120408) was prepared, and this base material was
Heating and holding at 200℃, AlCl33% by volume, CO□1
．． A mixed gas consisting of 5% by volume and the remainder H2 was heated to 10 Torr.
r for 1 hour and coated with Al2O3 to a thickness of 5 μm (Tool A).

The same base material as this tool A was heated to 5μm of aluminum at 1000℃.
2O, and the resulting tool is designated as B.

When the adhesion strength between the coating film and the base material was measured for the thus obtained tools A and B using the Ray Test/Automatic method as described above, the load Lc for tool A was 42N, whereas for tool B it was It was only 21N.

In addition, 10
Cutting tests were conducted under the following conditions on tool C obtained by coating Al2O3 to a thickness of 1 .mu.m at 00.degree. C. and on a tool consisting only of the base material.

Work material: SCM435 (Ha = 280) V = 6
00m/m1n f = 0.36mm/rotation d = 2 mtn Holder: F NIIR-44A Cutting agent: Not used Cutting time: 10 minutes As a result of this cutting test, tool A has flank wear of 0.31
On the other hand, tool B had flank wear of 0.5n or more at the cutting time of 2 minutes and 15 seconds and became unable to cut, and tool C also had flank wear at the cutting time of 6 minutes and 11 seconds. 0.5111ff1 or more, and for the tool, the flank wear after cutting for 3 minutes and 38 seconds was 0.5111ff1 or more.
The diameter exceeded 5 mm, making it impossible to cut any of them. This result fully proves the effectiveness of the present invention.

Example 2 313N485% by weight, ZrozlO weight I%, Y2O3
Ceramic sintered body consisting of 5% by weight Model number: 5NG
N120408> was prepared, and this base material was heated and held at 1150°C to form AlCl32.5% by volume, CO22% by volume,
A mixed gas consisting of the remaining H2 was flowed at 15 Torr for 1 hour to coat the tool E) with Al2O3 to a thickness of 4 μm. Tool E
The same base material was coated with 4 μm of Al2O3 at 1000°C to obtain tool F, and then similarly coated with Al2O3 at 1000°C.
A tool G coated with 1 μm of Cutting tests were conducted on the tools E to G thus obtained under the following cutting conditions.

Work material: Cast iron FC25 V = 700m/m1n f = 0.36mm/rotation d = = 2mrn Holder: F NIIR-44A Cutting agent: Not used Cutting time: 5 minutes As a result of this cutting test, the flank of tool E Wear is 0.2
4 m, whereas the flank wear of tools F and G was 0.72 m+n and 1 order or more, respectively, and furthermore, tool G required only 3 aon to reach flank wear of 1 aon.
It was minutes and 14 seconds. It should be noted that a commercially available sintered tool made of Al2O3/TIC produced a chip after cutting for 4 minutes and 6 seconds.

Example 3 Eleven samples HR were prepared by applying Al2O3 coating to the same base material as in Example 2 under various conditions. Coating temperature, A
The l2O5 film thickness and the cutting test results conducted under the same conditions as in Example 2 were as shown in the table below.

Table 1 Effects of the Invention As described in detail above, according to the method of the present invention, the ceramic sintered body base material is carefully selected, the thickness of the coating Al2O3 films is limited within a predetermined range, and the Al2O3 coating treatment temperature is Based on the value set within a specific range, it is possible to provide a coated ceramic tool that satisfies two important requirements for ceramic tools at the same time, namely wear resistance and toughness, and that has sufficient durability for practical use. did it. This is a ceramic sintered body base material and A1□0. The adhesion strength with the coating layer was achieved by meeting the three requirements mentioned above, especially by increasing the coating treatment temperature higher than that of the conventional method. It has significantly improved flank wear and other properties compared to previous models.

Furthermore, in the method of the present invention, the CVD method, which is advantageous from the viewpoint of productivity and economy, can be used at a sufficient deposition rate under normal conditions. It's satisfying.

[Brief explanation of drawings]

Attached Figure 1 is a graph plotting the cast iron cutting test results using a conventional ceramic tool, and Figure 2 shows that the flank wear of the coated ceramic tool obtained by the conventional method was 0. This is a graph plotting the variation in the time taken to reach 3 mm. FIG. 3 is a graph plotting the relationship between the coating film formation temperature and adhesive strength (critical load + Lc) by various film forming methods. Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (3)

[Claims] (1) Ceramic sintered body base material at 1150-1500℃
1. A method for producing a strong ceramic tool, which comprises heating and maintaining the tool at a temperature within the range of 100 to 100 μm, and coating the surface of the tool with an Al_2O_3 thin film having a thickness of 0.5 to 20 μm by chemical vapor deposition. (2) The ceramic sintered body base material has Al_2O_3 as a main component and contains at least one component selected from the group consisting of TiC, TiN, Ti(CO), WC, and ZrO_2 in a proportion of 5 to 50% by weight. A method for manufacturing a tough ceramic tool according to claim 1, characterized in that the tool comprises: (3) The ceramic sintered body base material mainly contains Si_3N_4, ZrO_2, TiN, Y_2O_3, Al
The method for manufacturing a strong ceramic tool according to claim 1, characterized in that the tool contains at least one selected from the group consisting of _2O_3 and AlN in a proportion of 5 to 50% by weight.