JPS63176444A - Hyperfine-grained high cemented carbide alloy - Google Patents

Abstract

PURPOSE:To manufacture a hyperfine-grained high cemented carbide improved in wear resistance, chipping resistance, and toughness, by specifying the grain size of WC and the content and composition of a binding metal phase, respectively, in a cemented carbide alloy consisting of a hard phase of WC and a binding metal phase. CONSTITUTION:In the cemented carbide alloy consisting of the hard phase of WC and the binding metal phase, the average grain size of WC is regulated to <=0.4mu and the binding metal phase is also regulated so that it comprises 5-50wt.% and has a structure which is principally composed of one or two elements among Co, Ni, and Fe and in which one of >=2 elements among Cr, Mo, and W are allowed to enter into solid solution. Moreover, the total amount of one or >=2 elements among Cr, Mo, and W existing in the form of solid solution in the binding phase is regulated to 0.5-20wt.% based on the total binding metal phase.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to ultrafine grain cemented carbide.

[Conventional technology]

Conventionally, tungsten carbide (hereinafter referred to as W) with an average particle size of 1 μm or less
The main component of the bonded metal phase of the ultrafine-grain cemented carbide is Co, and in order to suppress the growth of WC grains during sintering, vanadium carbide (hereinafter referred to as VC) and chromium carbide (
Tantalum carbide (hereinafter referred to as Cr, C2)
In general, 0.1% to 2.0% by weight of grain growth inhibitors such as However, the average grain size of WC of these commercially available ultrafine grained alloys is 0.6 to 0.7 μm.

In addition, some alloys with even finer grained WC have recently been announced as ultrafine-grained cemented carbide (Nikkan Kogyo Shimbun 1986).
．． 8.12) The WC average particle size is 0.55 to 0.6 μm, and the WC particles do not have an average particle size of 0.4 μm or less.

[Problem that the invention seeks to solve]

In this way, the current ultrafine grain alloys use fine grain W as the starting material.
The basic concept is to use C and add a grain growth inhibitor to form a CO alloy gold binding phase, and therefore, at most WC
There are only alloys with an average grain size of around 0.6 μm.As an ultrafine grain alloy, the finer the WC average grain size, the better the strength, chipping resistance, and wear resistance.
Although various studies have been made to improve the manufacturing method of CM materials, the current limit is around 0.6 μm as described above.

Therefore, an object of the present invention is to provide an ultrafine-grained cemented carbide having an even finer WC average grain size.

[Means for solving problems]

This invention was developed in accordance with the above-mentioned objective, and its gist departs from the basic concept of the conventional W C--Co grain growth inhibitor, and uses Co as the binding metal phase.

It is characterized by being a fine-grained alloy with an alloy metal phase composed of a metal selected from Ni, Fe, Cr, Mo, and W.

This invention will be explained in detail below.

The present inventor discovered the following fact while investigating the grain growth process of fine-grained alloys. When a general ultrafine-grained alloy is prepared by using a commercially available WC powder with an average grain size of 0.6 μm and adding a grain growth inhibitor and Go, an ultrafine-grained alloy with a WC average grain size of about 0.7 μm can be obtained. The average WC particle size varies slightly depending on the type of grain growth inhibitor, but is generally around 0.7 μm. However, when examining the WC particle size after mixing and pulverization during alloy production, the WC used as a starting material with an average particle size of 0.6 μm was pulverized to 0.1 to 0.3 μm. What this means is that WC grains grow during sintering and
．． The grain growth mechanism is that the solid solution of WC into the CO binder phase and the precipitation of the dissolved W and C onto the existing WC particles occur continuously (Ostwald growth). It is. As is well known, <Co is 2 at 1400℃
Since 0% or more of W is dissolved in solid solution, as long as CO is used as the binder phase, grain growth due to the above-mentioned solid solution and precipitation will inevitably occur even if a grain growth inhibitor is added.

From this point of view, the present inventor investigated various bonding metals in which solid solution of W is small at high temperatures, and basically C0-N i -C
r, Co-Ni-Cr-Mo and Co
- By using an alloy consisting of Ni-Fe-Cr etc. as a binder phase, the solid solubility limit of W is small, so grain growth due to solid solution and precipitation of WC can be almost completely suppressed, and the 0.
An ultrafine-grained alloy made of WC with a grain size of 1 to 0.3 μm was obtained. This alloy according to the present invention and the conventional W C-
The first photograph of the fracture surface of a fine-grained alloy made of a Co-grain growth inhibitor is shown below.
As shown in the figure.

Next, we will explain the reason for limiting the numerical values.

If the content of the binder metal phase is less than 5% by weight, the toughness will be significantly deteriorated, and if it exceeds 50% by weight, the wear resistance as a tool will not be satisfied.

Furthermore, in the alloy of the present invention, the main component of the bonding metal phase is Co.

Iron family members such as W and Fe, including Cr and Mo.

One or more types of W have a 0.
5 to 20% by weight of solid solution. This solid solution C
If r, Mo, and W are less than 0.5% by weight, they will not have the desired grain growth suppressing effect, and if they exceed 20% by weight, the toughness will deteriorate, so it is essential that they be dissolved in the above proportions. becomes.

〔Example〕

Example 1 Commercially available WC powder (average particle size 0.67 zm), TaC (1.5 μm), VC (1.0 μm), water atomized N
i-Cr powder (5.0 μm), CO powder (1.0 μm)
After a predetermined quantitative amount, wet mixing and pulverization was performed using a . Thereafter, it was molded into a size of 4×8×25 and vacuum sintered at 1350° C. for 1 hour to produce a test piece.

Table 1 shows the physical properties of the alloy of the present invention.It is seen that the grain size is much smaller and the toughness is higher than that of the comparative alloy.

Example 2 An end mill with a diameter of 10 mm was prepared using the alloy shown in Table 1, and a chip cutting test was conducted using an oil-based cutting oil under the conditions shown in Table 2. The results are shown in Table 3. Since the alloy of the present invention has fine grains, it is recognized that both the chipping occurrence rate and the wear resistance are extremely excellent. Incidentally, the first chipping occurrence rate is the sum of the lengths of chipped cutting edges divided by the sum of all the lengths of cutting edges, and is expressed as a percentage.

〔Effect of the invention〕

As described above, according to the present invention, the conventional fine-grained WC-Co
-0, which was impossible with the basic concept of a grain growth inhibitor.
It is possible to produce cemented carbide (WC) with an average grain size of 4 μm or less, and this makes it possible to significantly improve wear resistance, chipping resistance, and toughness, for example, in end mill cutting. It goes without saying that the ultrafine-grained alloy of the invention is a new ultrafine-grained cemented carbide that is completely different from conventional ultrafine-grained alloys.

[Brief explanation of the drawing]

Fig. 1 is an SEM photograph of a fracture surface to show the difference in grain size between the present invention alloy and a conventional ultrafine-grained cemented carbide. b) The figure shows a photograph of the structure of a conventional ultrafine-grained cemented carbide.

Claims (2)

[Claims] (1) In a cemented carbide consisting of a hard phase of tungsten carbide and a bonding metal phase, the average grain size of tungsten carbide is 0.
．． 4 μm or less, the binding metal phase is 5% by weight or more, 50
% by weight or less, and the binding metal phase is mainly composed of one or more of Co, Ni, and Fe, and one of Cr, Mo, and W.
An ultrafine-grained cemented carbide comprising one or more species dissolved in solid solution. (2) In the cemented carbide according to claim 1, the total amount of one or more of Cr, Mo, and W dissolved in the binder phase is 0.5 with respect to the total binder metal phase. An ultrafine cemented carbide having a content of % by weight or more and 20% by weight or less.