JPS5867857A - Coated sintered hard alloy and preparation thereof - Google Patents

Abstract

PURPOSE:To prepare a coated sintered hard alloy excellent in heat shock resistance and tenacity, by a method wherein parts comprising a sintered hard alloy having a hard phase consisting of WC and B-1 type solid solution bonded by a ferrous metal therein is heated in an N2 atmosphere and a TiC film is applied to the heated parts to enhance the bonding strength of the film. CONSTITUTION:Parts comprising a sintered hard alloy containing WC and B-1 type solid solution as hard phases bonded by a ferrous metal is held at 1,200- 1,600 deg.C for 10min-5hr in an atmosphere of which N2 partial pressure is 1- 700 torr to enrich the surface thereof with the B-1 type solid solution. In the next stop, TiC is coated on the surface thereof. By this method, adhesion strength between a sintered hard matrix material and the TiC film is improved and a coated sintered hard alloy excellent in heat shock resistance and mechanical tenacity can be obtained.

Description

[Detailed description of the invention] The present invention relates to coated cemented carbide parts.

Coated cemented carbide, which is made by coating cemented carbide with a TiO hard film, has excellent wear resistance, melt resistance, and chemical reaction resistance, and is widely used in practical use. There are many limitations from a practical standpoint, such as the adhesive strength between the I7 base and the coating being not yet sufficient, making the finish unusable, and not being suitable for use with cutters. This adhesive strength is not only affected by physical and chemical bonding between the substrate and the coating material, but also by differences in thermal expansion during cutting. In addition, particularly when chemical vapor deposition is used as a surface coating method, a decarburized phase called an eta phase is generated on the substrate immediately below the coating, reducing the interfacial strength. For this reason, various plans for improving the interface strength have been studied to date. For example, the substrate may have a slightly different composition than conventional cemented carbide, i.e., the Oo gold metal content may be reduced to increase the chemical bond strength, or the NbO content may be increased to increase the chemical bond strength between the substrate and TiO. Attempts are being made to bring the coefficient of thermal expansion closer to that of Regarding the generation of eta phase, for example, it is called carburizing treatment, and O
A method is used in which the generation of eta phase is prevented by diffusing 0 from the surface of the substrate using a mixed gas of H4+HI or the like.

However, the reality is that these methods are not sufficiently effective. The reason for this is that 00 in the base cannot be reduced below a certain amount from the viewpoint of toughness, or in the case of carburizing, the treatment time is as long as 2 to 4 hours, and the amount of 0 carburized is adjusted depending on the amount of 0 contained in the base. Although it is necessary to do so, it is difficult to do so in practice.

The object of the present invention is to improve the above-mentioned drawbacks of the prior art, improve the adhesive strength between the cemented carbide base material and the coating, and provide a novel coated cemented carbide that has excellent thermal shock resistance and mechanical toughness.

The feature of the present invention is that a cemented carbide substrate having almost no OO present on its surface and enriched with a B-1 solid solution carbide phase is used, and the surface of the substrate is directly coated with OO. The B-1 type solid solution is a Na0t type crystal structure compound consisting of one or more carbides and superoxides of metals in groups 4&, 5a, and 6a of the periodic table. A method for obtaining such a substrate is already known in Japanese Patent Application Laid-Open No. 154561/1983.
This is possible by adjusting the N1 partial pressure in the sintering atmosphere. That is, the equilibrium 1i of the B-1 type solid solution of the carbide member
-By increasing the N2 partial pressure of the sintering atmosphere more than the partial pressure, 00 in E-IIJl almost completely disappears, and the surface is almost completely covered by the B-1 type solid solution.

The feature of the present invention is that TiO is coated on a substrate whose surface is enriched with this B-1 type solid solution.
JP-A-55-1 characterized by direct coating of rO@
This is an excellent point that is different from the invention described in Publication No. 541561.

First, the reason why the present invention is superior to conventional TiO-coated cemented carbide is that the eta phase, which is a brittle phase, is not generated when chemical coating treatment is performed. At the initial stage of the coating process, 0 diffuses from the substrate to the coating surface, so the generation of eta phase is unavoidable in conventional TiO-coated cemented carbide. However, in the present invention, the B-1 type solid solution is enriched on the substrate surface, and since the B-1 type solid solution has a large range of 0 bond ratio, even if O in the B-1 phase diffuses into the film, decarburization does not occur. The eta phase does not occur. Second, B-1 type solid solution and T
Since the difference in thermal expansion coefficient of the iO film is smaller than that between the substrate and the TiO film, there is little peeling of the film during cutting.

Thirdly, since Oo does not exist at the substrate-coating interface, the interfacial strength increases, and since there is no diffusion of Oo from the substrate to the coating, the abrasion resistance of the coating significantly improves.

Next, AI-
Compared to Hog coating, μgos coating has B
It is confirmed that W in the -1 type solid solution and AAmos cause a chemical reaction, and a very brittle W oxide is generated at the interface, resulting in deterioration of the interface strength. On the other hand, in TiO coating, TiO is B-
Since it is a component of the xlJTi solid solution, no embrittlement reaction phase occurs. This point was cited earlier in JP-A-55-154F1.
This cannot be easily deduced from the invention described in Publication No. 61.

Here, the amount of B-1 type solid solution near the substrate surface is at least 4
The reason why it is set to 0% by volume is that if it is less than 40%, there is a risk that eta phase will occur when chemical coating treatment is performed, and the difference in thermal expansion between the substrate and the film will not be sufficiently reduced, and the peel strength during cutting will not improve. Also, the reason why the Oojii near the base surface was set to be less than 20% of the Oo content inside the cemented carbide was 20%.
If it exceeds this, the adhesive strength with the film will deteriorate and the abrasion resistance of the film will decrease. Next, the reason why the area near the surface is defined as "at least 1 μm" is that if it is less than that, eta phase, peeling, etc. will occur during cutting.

In addition, in enriching the 1-1 type solid solution on the substrate surface,
The reason why N1 partial pressure was set from 1 to 700 Torr is l'ro
If it is less than 700 Torr, the effect will not be sufficient (if it exceeds 700 Torr, the surface roughness will deteriorate and it will not be suitable as a TiO-coated carbide member.
The reason for limiting it to C is that at temperatures exceeding 1600 C, the carbide of the substrate will grow coarsely, making it unusable for practical use.
This is because the effect of M2 gas is not sufficient at temperatures below 2001°.

Example 1) Powder was blended into a composition of 2WO-10Tio-10TaO-80o, sintered in vacuum at 14,000°C for 1 hour, and then Hl gas was introduced at 5 Torr and cooled as it was to produce a cemented carbide base (4). did. At the same time, a substrate (B) in which 311 gas was not introduced was prepared as a comparison material. Next, a chemical vapor deposition process was performed on this substrate using TiO4, Ha, and 0)14 gases to coat the substrate with a Tie film having a thickness of 6 μm.

These two types are cut under the following cutting conditions: Work material: f90M3 Cutting speed: 250117win Feed: 04111/r@T
Depth of cut: L5m11 A cutting test was conducted using water-soluble cutting oil.

While the comparative product B chip could only be cut for 15 minutes due to peeling of the coating, the whip of the present invention did not peel off even after cutting for 30 minutes and showed a good vehicle shape.

Example 2 79WO-3TiO-3TiN-4TaO-2NbO-
Mix the powder to a composition of 90o and heat at 140o r in vacuum.
Sintering is carried out for a period of time, followed by 100T o of Ha gas.
A cemented carbide substrate (0) was prepared by introducing rr and cooling in a furnace. At the same time, as a comparison material, N and base C were not introduced with gas.
D) was produced. Next, a chemical vapor deposition process was performed on this substrate using Ti0Aa, H, and OH* gas to coat Too to a thickness of 6 μm. Next, when we observed the cross sections of these two types, no eta phase was observed in (0), but in (D), there was no eta phase observed just below the surface of the substrate.
Eta phase was observed over a thickness of ~3 μm
Cutting was performed using a 200 m/mn feed rate α4 open/rsv depth of cut L5 simple work material 80M3 1ow with a groove.

Comparative chip (9) broke after 15 impacts, but chip (0) of the present invention did not break even after 500 impacts. In this way, Oo on the surface was reduced, and B- By coating T101 on a cemented carbide substrate enriched with type 1 solid solution, it is possible to prevent the generation of eta phase and obtain a coated cemented carbide that is resistant to thermal shock and mechanical shock.

41・To the Agency's Applicant +、y、ul cn'f"fj゛Coated cemented carbide and its manufacturing method Supplement 11:Tainame Village +50111 1shir affiliated corporation representative
Noshi and, 11th floor Norifuyo Kawa 1 person holi'! t cr>>, Y″″
% Claims” and “Detailed Description of the Invention” supplement “1”. ``P1 and 1 paper, D.

Contents of the amendment■ The statement in the "Claims" column of the specification is corrected as follows.

"A coated cemented carbide in which a hard phase of LWO and a B-1 type solid solution is bonded with an iron group metal and coated with TiO, at least 1 μm from the surface of the cemented carbide in contact with the layer to be laminated. The Oo content in the depth part is 140% or less of the 00 content in the interior of the cemented carbide, and the B-4 type solid solution is contained at 40% by volume or more and less than 80% by volume. coated cemented carbide.

& When applying the 'I'10 coating film on the surface of the cemented carbide parts, which are made by combining WO and B-4 type solid solution with iron group metals, the former cemented carbide parts were soaked in N snow in advance. 1200 C to 1 in an atmosphere with a partial pressure of 1 to 700 Torr
A method for producing a coated cemented carbide, characterized by holding at 600 C for 10 minutes to 5 hours. ” ■ The description in “Detailed Description of the Invention” in the specification is corrected as follows.

(1) After "No improvement" on page 5, line 17 of the specification, "Also, the reason why the percentage is less than 80% is that B-1 type solid solution is essentially brittle and tends to break if it exceeds 80%." .” is inserted.

(4) Insert the following sentence after "Produced." on page 6, line 18 of the Ministry of Health.

Next, as a result of fluorescent X@ analysis of the surface of (4), it was confirmed that the B-1 type solid solution was 72% by volume, the WO single phase was 27% by volume, and 00 was 1% by volume. , it was confirmed that on the surface of the substrate (B), the B-4 type solid solution was 38% by volume, the Wa single phase was 42% by volume, and 00 was 20% by volume.'' (5) Ibid., page 7, line 17. Insert the following sentence after "produced."

Record "The results of surface composition analysis are shown in the table below.

Table 1 ” that's all

Claims (1)

[Claims] In a test cemented carbide in which a hard phase is LWO and a B-1 type solid bath and is bonded with an iron group metal and coated with TiO, the superhard alloy in contact with the aI film is The Oo content at a depth of at least 1μ from the surface of the hard metal is 20% or less of the 00 content inside the cemented carbide, and the B-1 type solid solution is contained at 40% by volume or more. A coated cemented carbide characterized by: Z When applying a coating film of TiO to the surface of a cemented carbide part made by using WO and B-1 type solid bath as a hard phase and bonding them with an iron group metal, the former cemented carbide part was preliminarily coated with N. pressure is 1
~700 Torr (7) atmosphere 12oOC~16o
A method for producing a coated cemented carbide, characterized by holding the coated cemented carbide at oC for 10 minutes to 5 hours.