JP2002069562A - Ni BASED CERMET AND PARTS FOR PLASTIC MOLDING MACHINE AND FOR DIE CASTING MACHINE USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the wear resistance of an Ni based cermet without deterio rating its toughness. SOLUTION: As to the structure of the whole of an Ni base cermet, in a bonding phase (a) composed of an Ni-Si-Mo alloy or an Ni-Si alloy, spherical or lumpy hard aggregates (b) are dispersed. Then, as to the structure of the hard aggregate (b), a dispersed phase (d) composed of Ni-Mo borides having a grain size smaller than the size of the hard aggregate (b) is dispersed into the bonding phase (c) composed of an Ni-Si-Mo alloy or an Ni-Si alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Ni-based cermet having excellent toughness and wear resistance.

[0002]

2. Description of the Related Art Conventionally, mechanical materials that require extremely high wear resistance include alloys in which hard phases such as carbides, nitrides, and borides are bonded by alloys such as Fe, Co, and Ni, so-called cermets. Has been used. For example, a WC-Co alloy known as a cemented carbide is one of them. Also, TiC-Ni alloys have been put to practical use.

Recently, Ni-B-Mo alloys,
A Ni-B-Co alloy has been developed (for example, see Japanese Patent Application Laid-Open No. 8-134569 by the present applicant). Each of these cermets is a fine hard material, specifically several μm.
An alloy in which hard particles of m or 1 μm or less are bound by a metal binder phase.

[0004]

When such a cermet is used as a material for a machine part, it is often required to have not only wear resistance but also toughness. However, in the conventional cermet, when the content of the hard material is increased for the purpose of improving the wear resistance, the toughness of the alloy is reduced, and on the other hand, when the content of the metallic material is increased for the purpose of ensuring the toughness. It has the property that the wear resistance is reduced (that is, when the content of the hard material is reduced). For this reason, there is a problem that it is difficult to achieve both toughness and wear resistance.

The present invention has been made to solve the above-mentioned problems, and has as its object to provide a Ni-based cermet having both high toughness and high wear resistance.

[0006]

According to the present invention, the toughness and the wear resistance are made compatible at a high level by improving the material structure.

In general, if the content of the hard material contained in the material is the same, a relatively large hard material in the form of a sphere or a block is more indispensable than when the fine hard material is uniformly dispersed in the binder phase. The existing structure shows better wear resistance. However, on the other hand, alloys in which large hard particles are scattered have poor toughness. This is especially true for alloy tool steels (SKD1
1) and so on. It is considered that this decrease in toughness is caused by a difference in elastic modulus between the hard material and the metal material and a difference in thermal expansion coefficient. In order to improve the toughness of such an alloy, the amount of the hard material in the cermet should be reduced as described above. However, in that case, the wear resistance is reduced and the object of the present invention is achieved. Can not.

Therefore, in the present invention, the relatively large hard particles are replaced by aggregates of fine hard particles which are aggregated in a spherical or massive form, and the periphery thereof is bonded with a metal having excellent toughness to thereby provide resistance. It has been decided to improve toughness without lowering wear resistance. The Ni-based cermet according to the present invention exhibits excellent wear resistance as compared with a conventional cermet in which a fine hard material is uniformly dispersed in a binder phase. The Ni-based cermet according to the present invention (the alloy of the present invention) exhibits excellent characteristics that the decrease in wear resistance is small even when the content ratio of the metal in the cermet is increased for the purpose of improving toughness.

[0009] Specifically, the alloy of the present invention comprises a binder phase (a) composed of a Ni-Si-Mo alloy or a Ni-Si alloy and a spherical phase dispersed in the binder phase (a). Alternatively, the metal structure of the hard material aggregate (b) is Ni-Si-Mo.
A binder phase (c) composed of an alloy or a Ni-Si alloy, and a dispersed phase composed of a Ni-Mo boride having a particle diameter smaller than the size of the hard material aggregate (b) dispersed in the binder phase (c) ( d).

In producing the alloy of the present invention, it is preferable to use a Ni-Mo boride obtained by an atomizing method as a raw material and to perform molding by any of a vacuum sintering method and a hot isostatic pressing method. is there.

[0011] In the alloy of the present invention, the size of the hard material aggregate (b) is preferably 30 to 300 µm. The reason is that the size of the hard object aggregate (b) is 3
It is industrially difficult to reduce the thickness to 0 μm or less. On the other hand, if the thickness is 300 μm or more, the distance between the hard material aggregates (b) becomes large, so that the base portion, that is, the binder phase (a)
This is because the selective wear of the portion is likely to occur and the wear resistance of the entire alloy is reduced, and as a result of this selective wear, the portion of the hard material aggregate (b) becomes convex and accelerates the wear of the mating material. .

[0012] The composition of the alloy of the present invention is, by weight%, B: 0.
6-3.2%, Si: 0.5-8%, Mo: 5-24%,
It is preferable that the balance be Ni and unavoidable impurities. Preferably, C: 0.01 to 0.5% is added to the above composition. Further, the content of the dispersed phase (d) composed of Ni-Mo boride is preferably 7 to 34% by weight. Hereinafter, in the present specification, all percentages indicating the composition and the content mean% by weight unless otherwise specified.

Hereinafter, the reason why the above-mentioned components and the content of the dispersed phase (d) are specified will be described.

First, B lowers the sintering temperature of the alloy, forms borides with Ni and Mo, and enhances the wear resistance of the alloy. Since the transverse rupture strength is lowered regardless of whether the B content is high or low, the B content is set to 0.6 to 3.2%. The B content is more preferably set to 1.0 to 3.1%.

Next, Si lowers the sintering temperature in the same manner as B, so that it is effective to combine with steel at the same time as sintering, and to increase the transverse rupture strength of the alloy. is there. If the sintering temperature is low, sintering and compounding can be performed simultaneously without deteriorating the steel material, which is economically advantageous. The sintering temperature decreases as the Si content increases, but when it exceeds 8%, the transverse rupture strength sharply decreases. Even when the amount of Si is small, the bending strength decreases and the sintering temperature increases, so the lower limit is set to 0.5%. Therefore, the Si content is set to 0.5 to 8%. Note that the Si content is more preferably set to 2.5 to 7%.

Next, the Mo content (5 to 24%) and N
Content of i-Mo boride dispersed phase (d) (7 to
(34%) will be explained. Mo
Forms a boride (Ni-Mo boride) with B, has the effect of increasing the wear resistance and improving the corrosion resistance of the binder phase mainly composed of Ni. In addition, it has the effect of refining the crystal grains of the alloy and significantly increasing the strength and bending strength. Here, the wear resistance of the alloy depends on the content of Ni-Mo boride, and if it is 7% or less, sufficient wear resistance cannot be obtained. For this reason, the lower limit of the Ni-Mo boride content is set to 7%. In addition, in order to secure the Ni-Mo boride content of 7%, the Mo content needs to be 5% or more. For this reason, the lower limit of the Mo content is set to 5%. On the other hand, the upper limits of the Mo content and the content of the Ni-Mo boride dispersed phase (d) are determined based on industrial productivity. That is, as the Mo content increases, the melting point of the alloy increases, and the flow of the molten metal deteriorates when the molten metal is sprayed. When the Mo content is 24% or more, production of the raw material powder becomes practically impossible. The content of the Ni-Mo boride dispersed phase (d) corresponding to the Mo content is 34%. For this reason, the upper limit of the Mo content is 24
%, The upper limit of the content of the Ni-Mo boride dispersed phase (d) is 3
4%.

C is used for the purpose of lowering the sintering temperature, improving the sinterability, reducing the number of holes and the diameter of the holes in the sintered body, and further improving the thermal shock resistance. It is preferable to add from 01 to 0.5%.

The alloy of the present invention can be suitably applied to parts which come into contact with molten plastic of a plastic molding machine, for example, barrels and screws, and parts which come into contact with molten metal of a die casting machine for Al or Mg, for example, plunger sleeves. . In this case, from the viewpoint of cost, it is preferable that the base portion of the component is formed of a steel material and the portion that comes into contact with the molten plastic or molten metal is formed of the Ni-based cermet.

[0019]

The present invention will be described in more detail with reference to the following examples.

[First Example] As shown in Table 1 below, a material sample was prepared as a comparative example (conventional product) and a material sample was prepared as an example (inventive product).

[0021]

[Table 1] First, for the material of the comparative example (conventional product),
The powders of iB, Si, Mo, and Ni were weighed and blended to have the compositions shown in Table 1 and mixed and pulverized in ethyl alcohol by a rotary ball mill for 48 hours. Obtained. The raw material powder thus obtained is press-molded, sintered in a vacuum, and
A sintered body of 50 × 11 mm was obtained.

With respect to the materials of the examples (inventive products), first, powders of NiB, Si, Mo, and Ni were dissolved, and powders having compositions shown in Table 1 were prepared by a molten metal spraying method. Next, 30-300 μm
Only those having a particle size of 5 were sieved with a sieve having a predetermined mesh to obtain a raw material powder. Next, this raw material powder was
Fill into a 3 × 14mm iron container, sinter and φ50 ×
An 11 mm sintered body was obtained.

In Table 1, the hard material Ni-
Mo boride (Mo₂NiB₂) Is calculated as Mo
₂NiB₂The atomic weight ratio of each element in Mo₂: N
i: B ₂= 1: 0.306: 0.112
And calculate. In other words, taking the material as an example,
Content (wt%) = 20 (Mo₂) + 20 × 0.30
6 (Ni) + 20 × 0.112 (B₂).

Material (conventional product) and material (invented product)
1 (a) and 1 (b) respectively show the microstructure of the sintered body of FIG. FIG. 2 schematically shows the structure of the material (inventive product). As shown in FIG. 1B and FIG. 2, the structure of the material (inventive product) is Ni-Si-M
a binder phase (a) composed of an o-alloy or a Ni-Si alloy;
And a granular or massive hard material aggregate (b) dispersed in the binder phase (a), wherein the metal structure of the hard material aggregate (b) is made of a Ni—Si—Mo alloy or a Ni—Si alloy. (C), and Ni-Mo having a particle size smaller than the size of the hard material aggregate (b) dispersed in the binder phase (c).
And a dispersed phase (d) composed of boride.

On the other hand, the structure of the material (conventional product) is shown in FIG.
As shown in (a), the structure is such that a hard material (Ni-Mo boride) is uniformly dispersed in the binder phase.

Since the material (conventional product) is similar to the microstructure of the material (conventional product) and the material (inventive product) is similar to the material (inventive product), the photographs are omitted.

The above four types of materials were processed into predetermined dimensions, and the wear resistance was measured using an Ogoshi quick wear tester. Further, the fracture toughness value was measured according to JIS R1607. The conditions of the Ogoshi quick wear test are as follows.

Friction speed 2 m / sec Final load 18.6 kgf Friction distance 600 m / sec Counterpart material SKD11 (HRC58) The test results are shown in Table 1 and the graph of FIG. As can be understood from these figures and tables, the material (invention) is superior in wear resistance when compared with a material having the same hard material content. The fracture toughness value does not substantially change. Similarly, when compared with a material, the material (invention) is superior in abrasion resistance. The fracture toughness value does not substantially change. Furthermore, materials with low hard matter content (invention)
Even when a material having a high hard material content (conventional product) is compared with a material having a high hard material content, the material of the invention is superior in abrasion resistance.

From the above test results, the Ni-based cermet according to the present invention, in which fine hard objects are aggregated in a spherical or massive form and bonded around with a Ni alloy, is a conventional Ni-based cermet in which the hard objects are uniformly dispersed. It was found that the abrasion resistance was better and the toughness could be maintained at the same level as the conventional product.

[Second Embodiment] An example in which a plunger sleeve for a die casting machine, which is an example of a part that comes into contact with the molten metal of an Al or Mg die casting machine, is manufactured with the alloy of the present invention will be described with reference to FIG. .

First, a sleeve base 1 made of a steel material (S48C) having a shape as shown in FIG. 4A and a core 2 made of a steel material (S48C) having a shape shown in FIG. 4B. Were prepared by machining. After applying alumina as a release agent to the outer peripheral surface of the core 2, the two were assembled as shown in FIG.

Next, Ni- produced by the molten metal spraying method is used.
3.1% B-4.6% Si-20% Mo alloy powder 4 (average particle diameter 100 μm) was filled in the space between the outer peripheral surface 2a of the core 2 and the inner peripheral surface 1a of the base material 1. Thereafter, vacuum sintering was performed at 1040 ° C. The packing density at this time was about 60%. By this sintering, a Ni-based cermet layer 4 'was formed on the inner peripheral surface 1a of the substrate 1. The Ni-based cermet layer 4 '
The interface between the substrate and the substrate 1 was strongly bonded to the metal.

After sintering, the welded portion was removed and the core 2 was removed, followed by predetermined machining to complete the plunger sleeve 5 shown in FIG.

When the present plunger sleeve 5 was mounted on a die casting machine and the actual machine was operated, it showed a durability of 460,000 shots. This value was 4.5 times the life of the conventional sleeve (nitride product of SKD61) of about 100,000 shots, showing excellent results.

The parts of the plastic molding machine that come into contact with the molten plastic, for example, the injection barrel, can also be obtained by the same manufacturing method as described above.

[0036]

As described above, according to the present invention,
A Ni-based cermet having both high toughness and high wear resistance can be obtained.

[Brief description of the drawings]

FIG. 1 shows an alloy of the present invention (FIG. 1B) and a conventional alloy (FIG. 1B).
The photograph which shows the structure of (a)) in comparison.

FIG. 2 is an explanatory view schematically showing the structure of the alloy of the present invention.

FIG. 3 is a graph showing a comparison between the wear resistance of the alloy of the present invention and the conventional alloy.

FIG. 4 is a diagram illustrating a manufacturing process of a plunger sleeve lined with the alloy of the present invention.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shuhei Honma 2068-3 Ooka, Numazu City, Shizuoka Prefecture F-term (reference) 4T206 AJ02 AJ09 AJ14 JA07 JQ41 4K018 AA08 BA11 DA32 EA13 KA01 KA70

Claims (8)

[Claims] 1. A bonding phase (a) composed of a Ni—Si—Mo alloy or a Ni—Si alloy, and a spherical or massive hard material aggregate (a) dispersed in the bonding phase (a). b) wherein the metal structure of the hard material aggregate (b) is Ni-Si-M
a binder phase (c) composed of an o-alloy or a Ni-Si alloy;
The hard material aggregate (b) dispersed in the binder phase (c)
A dispersed phase (d) composed of Ni-Mo boride having a particle size smaller than the size of the Ni-based cermet. 2. The size of the hard object aggregate (b) is 30.
The Ni-based cermet according to claim 1, wherein the thickness of the Ni-based cermet is from 300 to 300 m. 3. The Ni-based cermet according to claim 1, wherein the content of the dispersed phase (d) is 7 to 34% by weight based on the entire Ni-based cermet. 4. B wt .: 0.6-3.2% by weight, Si:
2. The composition according to claim 1, comprising 0.5 to 8% and Mo: 5 to 24%, the balance being Ni and unavoidable impurities.
The Ni-based cermet according to 1. 5. B: 0.6 to 3.2% by weight, Si:
0.5 to 8%, Mo: 5 to 24%, C: 0.01 to 0.5
%, And the balance consists of Ni and unavoidable impurities. 6. The Ni-based material according to claim 1, wherein the Ni-Mo boride obtained by the atomizing method is formed by vacuum sintering or hot isostatic pressing. cermet. 7. The N according to claim 1, wherein
A part for contacting molten plastic of a plastic molding machine, characterized in that at least a part thereof is formed by an i-based cermet. 8. The N according to claim 1, wherein
A component which is in contact with a molten metal of a die casting machine for Al or Mg, at least a part of which is formed by an i-based cermet.