JPH01234168A - Coated abrasive grain and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain surface coating showing adhesion and acid resistance on the surface of abrasive grains by applying a simple immersing process of using fused salt bath. CONSTITUTION:Fused salt bath such as fused hologenide bath is modified by addition of at least one of metal, alloy, hologenide and oxide of target metal. Abrasive grains such as diamond abrasive grains are immersed in this immersing bath to coat these abrasive grains with compound (at least one of carbide, boride, nitride and silicide) of the target metal. Super-rigid abrasive grains having a good acid resistance, abrasion resistance and coating adhesion can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to coated abrasive grains, and particularly to a method for producing coated abrasive grains by a dipping method. More specifically, the present invention relates to a method for producing abrasive grains coated with a metal compound layer comprising at least one of metal compounds, such as metal carbides, metal borides, metal nitrides, and silicides, using a molten salt bath.

(Prior Art) Abrasive grains, such as diamond abrasive grains and hard BN abrasive grains, are called ultra-hard abrasive grains, and are widely used as raw materials for grindstones and as abrasive materials. In particular, natural or artificial diamond abrasive grains are usually bonded using metals, synthetic resins, or glassy inorganic substances as binders, and used as grinding wheels for grinding cemented carbide tools, ceramics, ferrite, glass, etc. It is used in a wide range of fields such as grinding hard materials and cutting stone and concrete. In particular, with the remarkable development of ceramic materials in recent years, diamond grindstones and hard BN grindstones that enable high-precision grinding of ceramic materials have been used in large quantities.

However, the abrasive grains used today have the following drawbacks.

For example, in the case of a resin bonded whetstone or metal bonded whetstone whose main component is diamond abrasive grains, a metal such as nickel (Ni) is added to the surface of the abrasive grains to increase the bonding strength with the resin or metal that is the binder.

Covering is being done. Such a metal coating is said to have the effect of preventing the resin from deteriorating due to the heat generated at the tips of the abrasive grains during use of the whetstone. However, a problem arises in that such a metal coating layer causes clogging of the grindstone.

On the other hand, vitrified bond grindstones, which also have diamond abrasive grains as their main component, use ceramic as a binder and are manufactured by high-temperature firing, so the bonding force between the abrasive grains and the binder is strong due to solid phase reaction. However, there is a problem that thermal corrosion of the diamond abrasive grains occurs in such a high-temperature firing process, making manufacturing difficult.

Recently, in order to prevent oxidation of the abrasive grains during grindstone manufacturing, improve film adhesion, and prevent clogging during grinding, the surface of diamond abrasive grains has been coated with Ti (C, N, O) by chemical vapor deposition.
JP-A No. 55-162499 discloses coating with . However, this method is said to be still insufficient in terms of film adhesion.

As described above, the advantages of coated abrasive grains are being recognized, and several proposals have been made to improve the coated abrasive grains. However, all of these methods are based on vapor phase deposition methods such as the CVD method, and due to their nature, they cannot be mass-produced, require large-scale equipment, and are expensive methods.

Therefore, in order to fully exhibit the above-mentioned excellent effects of coated abrasive grains, there is a need for a significant improvement in film adhesion by a simple and inexpensive means.

(Problem i1 to be Solved by the Invention) Thus, an object of the present invention is to provide ultra-hard coated abrasive grains that have excellent oxidation resistance, wear resistance, and film adhesion, and a method for producing the same.

Furthermore, another object of the present invention is to provide ultra-hard coated abrasive grains with excellent oxidation resistance, abrasion resistance, and film adhesion that can be produced in large quantities and at low cost compared to the CVD method, and a method for producing the same. be.

(Means for Solving the Problem) By the way, one of the applicants for this patent previously proposed a method of using a molten chloride bath as a hardening coating method for the surface of a metal material. Refer to Japanese Patent Application Laid-Open No. 61-87873. It can be seen that this method significantly increases the hardness of the surface of the metal material and significantly improves the wear resistance.

Further research revealed that such a method can be applied not only to metallic materials but also to non-metallic materials, and in particular, for non-metallic materials, it is not only possible to simply improve the hardness, but also to improve the hardness of non-metallic materials. It has been found that by partially roughening the surface to be treated, the adhesion of the film can be significantly enhanced.

Therefore, when we investigated the application of such a dipping method to achieve the above-mentioned objective, we found that the effect is particularly remarkable in coating the surface of abrasive grains, and thus completed the present invention.

Therefore, the gist of the present invention is a coated abrasive grain in which a coating made of at least one of carbides, borides, nitrides, and silicides of a target metal derived from a dipping method is provided on the surface of the abrasive grains. .

Furthermore, from another aspect, the gist of the present invention is to
A method of forming a coating consisting of at least one of carbides, borides, nitrides, and silicides of a target metal on the surface of abrasive grains by a dipping method, the method comprising dipping in a molten salt bath containing the target metal. The process is characterized by preparing a bath, and then immersing the abrasive grains to be treated in the bath for a suitable time.
This is a method for producing coated abrasive grains.

According to a preferred embodiment of the invention, the molten salt bath may be a molten halide bath.

Further, the molten salt bath may be at least one molten salt bath selected from the group consisting of carbonates, phosphates, ferrates, aluminates, and silicates.

Further, the molten salt bath may be a fluoride-containing halide bath.

Further, the molten salt bath may be at least one molten salt bath selected from the group consisting of fluoride-containing carbonates, phosphates, ferrates, aluminates, and silicates.

Here, the above-mentioned "immersion method" is generally a method in which the above-mentioned abrasive grains are immersed in a molten salt bath to form a surface coating. Such dipping treatment may be repeated two or more times by using a different type of target metal. In addition, when using the coated abrasive grains of the present invention, the coated abrasive grains may be used as they are, or if necessary, Post-treatment such as coating with a metal compound, single metal, or alloy by plating or the like may be performed.

In a preferred embodiment of the present invention, the abrasive grains are diamond abrasive grains or hard BN abrasive grains. In the case of metal carbide coatings, especially when using hard BN as abrasive grains, it is preferable to use carbon-deposited hard BN abrasive grains.Also, if you want to thicken the metal carbide coating layer, carbon-deposit diamond abrasive grains. Diamond abrasive grains coated with a carbonaceous film may also be used, and the carbon in the surface layer of the abrasive grains reacts with the metal in the immersion bath to form a carbide film. Alternatively, if hard BN abrasive grains are immersed as they are, a type of substitution reaction will occur, causing B to be replaced with the metal in the immersion bath, forming a film made of metal nitrides originating from the immersion bath. Ru.

As already mentioned, said molten salt bath is preferably a molten halide bath, said halide comprising at least one of alkali metal and alkaline earth metal chlorides, and said fluoride comprising at least one of alkali metal and alkaline earth metal chlorides. Consists of at least one type of alkali metal and alkaline earth metal fluoride.

The halides include chlorides, oxalides, iodides, and even fluorides.

(effect) Next, the present invention will be explained in more detail.

The molten chloride bath as a typical example of the molten salt bath constituting the immersion bath used in the present invention is generally KCQ
The basic composition is BaCQz, or it has a fluoride added thereto, such as NaF. In addition, typical examples of molten chloride baths include NaQ2, LiCQ
Examples of fluorides include NaF SKF% LiF s CaFz, BaF
There are l etc. Preferably, a bath composition consisting of an alkali metal chloride-alkaline earth metal chloride or a bath composition consisting of an alkali metal chloride-alkaline earth metal chloride-alkali metal fluoride is preferable, and the specific composition ratio at that time, etc. As is clear to those skilled in the art from the above explanation, in general, Ka2-Bac12g-Na
For F series, KC! 2 is 5 to 95 mol%, Ba CQ
t is 5-95 mol%, and NaP is 5-50 mol%. If the fluoride content exceeds 50 mole percent, not only will the bath temperature become too high, but corrosion problems will occur.

As a modification, oxalide, iodide, or fluoride may be used in place of the chloride in the molten salt bath, and even in that case, the oxalide, iodide, or fluoride may be alkali metal or alkali. An appropriate material may be selected from oxalides, iodides, and fluorides of earth metals.

In addition, the molten salt bath may include carbonates, phosphates, ferrates,
It may also be a molten salt bath of aluminates and silicates; even in these cases alkali metal or alkaline earth metal salts are preferred.

Therefore, carbonates include carbonates of alkali metals or alkaline earth metals (e.g. LizCOs, KICOs).
2, Na2CO3,5rCOs, BaC05) are preferred. The compounding ratio is, for example, K1CO540n+olχ
, CaCO360+aolχ, or Na*CO*
30aolχ, K, CO324,51101χ, CaC
0145.5molX.

Phosphates include alkali metal or alkaline earth metal phosphates (e.g. NaPO5, Kpos, LiPO5
, KHzPO4, KJPOa, NaHPO,,5rs(
PO4)z-Ca(Pot)i, BaHPOa) is preferred, and its blending ratio is, for example, NaPo.

40+aolχ, KPOs 60 solχ, or NaPO532aolχ, KPOs 48aolχ, N
aF 20aolχ.

As the ferrate, ferrates of alkali metals or alkaline earth metals (e.g., KtFex04, Ca5iOs) are preferable.
FezO450s+olχ.

Examples of the aluminate include alkali metal or alkaline earth metal aluminates (e.g. K t AQO0
(NaAQOg, BaAQtOt) is preferable, and the compounding ratio thereof is, for example, NaF 50so1χ, KtAQtO4
It is 50 molχ.

Silicates include alkali metal or alkaline earth metal silicates (e.g. CaSiO3, NatSiOs, L
i2SiO3, Ba5ins, MggSi*Os) is preferable, and the blending ratio thereof is, for example, LixFt:CaFt:
LixSiOs:Ca5iOs =52.7:32.3
:9.3:5.7Peng o1χ.

The type of target metal is not particularly limited, but since one purpose of the treatment method according to the present invention is to improve the adhesion of the coating to the abrasive grains to be treated, hard metals that have been considered difficult to form a coating on, for example, Sib Cr, V, BSW, M
Metals from Group Na, Group Va, and Group Vla of the periodic table, such as Tis Zr%Hf, Nb, and Ta, are preferred.

Such target metals are added to the above-mentioned molten salt baths, in part as compounds, typically oxides or even halides, which are readily available and also - can be handled by boat fishing. This is advantageous because it is easy. In addition, the other part is added as metal powder. This may be added as a simple substance of the target metal or an alloy containing it, such as a ferroalloy (this is also an advantage of the present invention).

The target metal is added in the form of at least one of its single metal, alloy, halide, and oxide, and specific preferred combinations thereof include the following.

■ Elemental metals or alloys and oxides, ■ Elemental metals or alloys and halides, ■ Elemental metals or alloys, ■ Metal halides, ■ Oxides and reducing metals.

In this way, when adding an oxide of the target metal, if sodium metal fluoride is used as the fluoride, the oxide reacts with NaF in the molten salt, and the fluoride metal potassium, soda, etc. are partially added. generate. And they are respectively, for example, Ti0g→Nal[=TiFhs Cr40
．． →NaCrFs, V*0s-Na*VF6, BtO
s→KBF4, WO, - to □-F6. Then, they react on the surface of the abrasive grains to be treated, and each T
i-C (Tic), Cr-C (CrtCs, Cr*C2
, Crt*Ch), V-C(VzCSV*Cs, V, C
, VCe, ms), B-C, WC, etc. It is thought that the simple metal or alloy acts as a reducing agent for the metal added as an oxide.

Using fluoride in this manner further increases the coating speed.

In the case of adding a single metal or alloy, the surface of the commonly used metal or alloy is thought to be slightly oxidized, and it is not considered to be an academically pure metal.

Other metal halides, either single metals or in combination with alloys, are coated at favorable rates. However, in the case of only a metal halide compound, the rate is slow, and the reason for this is thought to be that there is no metal to reduce the metal halide.

However, even if only a metal halide is used, it can be coated because it is reduced to some extent by the abrasive grains to be treated (diamond, SiC abrasive grains).

When only an oxide is used, it is considered preferable to always add a reducing agent to reduce the oxide.

There is no limit to the amount of target metals or alloys added, but the amount of oxides of such metals in the immersion bath is 2.
% by weight is sufficient. If it is too small, a film of sufficient thickness cannot be obtained; the practical lower limit is about 1%.

On the other hand, if it is too large, the thickness of the coating such as the carbide layer may become uneven.

Addition of up to about 7% is allowed in practice. Preferably 5
~7% by weight.

In the case of halides of the target metal, the content may be up to 40%, but if it exceeds this, there will be problems with corrosion of equipment such as equipment.
In addition, halogen gas is generated in large quantities, resulting in sanitary problems.

When using an oxide of the target metal, it is preferable to add a reducing agent to reduce the oxide.

Reducing agents include Mn5AQSCa, Si, Ti,
Zr etc. or alloys thereof such as Fe-Mn s F
e-AQ%Fe-Ti.

Fe-Zr 5Fe-5i 5Ca-5i %CaCa
-5i-, which has a greater affinity with oxygen than chromium or Group Va elements, is used. The appropriate proportion of these reducing agents in the treatment bath is about 2 to 20% by weight.

If the amount is less than 2% by weight, the reducing effect will be insufficient, and if it exceeds 20% by weight, the formation of carbides will be hindered. Preferably it is 5 to 15% by weight.

Although the immersion time and temperature in the immersion method according to the present invention vary depending on the type of the intended metal compound to be produced, generally it is sufficient to treat at 700 to 100°C for 1 to several hours.

Incidentally, the ultra-hard abrasive grains used in the present invention are preferably diamond abrasive grains, hard BN abrasive grains, or a mixture thereof. The type of diamond abrasive grains is not particularly limited, and may be either natural or artificial.

There is no particular restriction on the particle size of the diamond abrasive grains or hard BN abrasive grains used as a grindstone using an appropriate binder, but
In general, it is preferable that the thickness is about 140-170 meshes or 50-60 meshes.

Although it is not necessary to particularly pre-treat the diamond abrasive grains and hard BN abrasive grains prior to the immersion treatment, it is preferable to perform a treatment such as degreasing to further improve film adhesion.

Incidentally, the film formation by the dipping method according to the present invention may be performed on abrasive grains which have been coated with an appropriate metal or alloy in advance by CVD or vacuum sputtering.

Furthermore, being "coated" with a metal element or alloy in this way may mean covering the entire body with those metals, or it may be obtained by plating the metal. It refers to something that has at least some metal on its surface. Examples of methods for this purpose include electroplating, electroless plating, the Cland method, physical vapor deposition (eg, varnish battering), and chemical vapor deposition (eg, vapor phase plating). Of course, the form of the abrasive grain itself is not limited in any way.

However, the coating previously provided in this way is not limited to the metal coating, and the same applies to the metal compound coating according to the present invention that has been explained so far. That is, the abrasive grain surface on which the metal layer or metal carbide layer has been formed in this way is treated again using a similar molten salt bath, preferably in this case the target metal is B, and the metal compound is B, for example. O
By using boron oxide such as , boron may be combined with the metal carbide already formed on the surface of the abrasive grain to form a metal boride. That is, a boron compound (e.g. boron dioxide) is prepared in a fluoride-containing molten salt bath, e.g. B20. → KBF4, which combines with, for example, Ti in the abrasive grain surface coating to form TiBz or TiBs, that is, Mn8 or 118 (M: metal)
It generates. Such treatment further improves the oxidation resistance of the abrasive grains. BSB! Similar to O3, S
Is S i O! Even in this case, Mo-5i is produced by combining with, for example, Mo in the abrasive grain surface coating.

Next, the present invention will be explained in more detail using Examples. In this specification, "%" means "% by weight" unless otherwise specified.

Ofunemasu 1 In this example, KCQ, BaCQz and N are placed in a porcelain crucible.
After adding 42.2, 20.2 and 37.6 mol% of aF respectively and heating and melting, predetermined amounts of each metal oxide, single metal or alloy powder (ferroalloy), and halide are added in appropriate combinations, The mixture was thoroughly stirred and used as an immersion bath.

Into the immersion bath prepared in this way, 2 g of diamond abrasive grains of 50 to 60 meshes (product name: MBS, manufactured by Company G, E) was added to the immersion bath.
It was immersed for only 2 hours at 50°C. Average coating thickness is 1.8μ
The combination of metal oxide and alloy used in this example and the composition of the resulting coating are shown in Table 1.

The above-mentioned abrasive grains were immersed in a stainless steel bottle (see Table 1).
The glass bottle was charged into a glass bottle with a diameter of 16.5 s + m x 30 ml and rotated for 15 minutes at a speed of 150 rp-, and the coating adhesion was determined by the ratio of the amount (weight) of the peeled coating at that time to the original weight. was evaluated.

The results are also summarized in Table 1.

Example 2 In this example, Experiment 1 of Example 1 was repeated with various changes in the type of molten salt bath. The immersion conditions were 950℃, 2
I went in time.

The results are the same as in the examples, including film composition, film thickness, and! l
The results are summarized as i-release film amount and shown in Table 2.

Test Magnet 12 shows an example using carbonate, Test Magnet 13.14 uses phosphate, Question Maru 15 uses ferrate, Question Maru 16 uses aluminate, and Arashi 17 uses molten salt made of silicate. .

2nd front and back 83 In this example, after adding 67.6 and 32.4 mol% of Ka2 and Baa2g to a porcelain crucible and heating and melting them, predetermined amounts of each metal oxide and single metal or alloy powder (ferroalloy) are added. In addition, appropriate combinations of halides were added and thoroughly stirred to prepare an immersion bath.

In the immersion bath thus prepared, 2 g of diamond abrasive grains of 50 to 6 o mesh (trade name: MBS, manufactured by Company G and E) were immersed at 950° C. for 2 hours. Average coating thickness is 1-2
The combinations of metal oxides and alloys used in this example and the resulting M compositions are as shown in Table 3.

Note that the abrasive grains mentioned above were immersed in a bath made of stainless steel.Table 3 Example 4 In this example, each coated diamond abrasive grain obtained in Example 1 was coated with a second boride film by the method according to the present invention. It was set up as a layer.

That is, boride formation begins with B20. and Fe-8 were added to the molten salt bath to prepare an immersion bath, and the procedure set forth in Example 1 was followed. Similar tests were conducted on the composition and peeling resistance of the resulting coating. The results are summarized in Table 4.

Table 4 Example 5 In this example, each coated diamond abrasive grain obtained according to Example 1 was provided with a silicide coating as a second layer, also by the method according to the invention.

That is, silicide formation was performed according to the procedure shown in Example 1 by first adding Sing and Si powder to the molten salt bath to prepare an immersion bath.

Note that the immersion treatment was performed at 950° C. for 1 hour.

The results are summarized in Table 5.

Table 5 (Note) Coating thickness - First layer carbide - Second layer silicide Example 6 In this example, metal layers of Ti and Mo (thickness approximately 2 μl 11) were previously provided on the diamond abrasive grains by chemical vapor deposition. Then, silicide formation was carried out in the same manner as in Example 5. The relationship between the obtained film composition and the metal layer that served as the base is shown in the sixth section.
They are summarized in the table.

Note that the immersion treatment was performed at 950° C. for 2 hours.

(Effects of the Invention) As described above, according to the present invention, a surface film exhibiting excellent adhesion and oxidation resistance, which could not be obtained conventionally, can be obtained by a simple dipping treatment using an easy-to-handle molten salt bath. Therefore, the present invention greatly contributes to the development of this industry.

Applicant: Takeo Oki (1 idiot) Agent Patent Attorney Akira Hirose -

Claims (9)

[Claims] (1) A coated abrasive grain comprising a coating formed by a dipping method on the surface of the abrasive grain and consisting of at least one of a target metal carbide, boride, nitride, and silicide. (2) The coated abrasive grain according to claim (1), wherein the abrasive grain is a diamond abrasive grain or a hard BN abrasive grain. (3) A method of forming a coating consisting of at least one of carbides, borides, nitrides, and silicides of the target metal on the surface of the abrasive grains by a dipping method, the method comprising: applying a single metal of the target metal to a molten salt bath; Coating, characterized in that an immersion bath is prepared by adding at least one of an alloy, a halide, and an oxide, and the abrasive grains are immersed in the immersion bath to coat the abrasive grains with a compound of the target metal. Manufacturing method of abrasive grains. (4) The method according to claim (3), wherein the molten salt bath is a molten halide bath. (5) The molten salt bath is at least one molten salt bath selected from the group consisting of carbonates, phosphates, ferrates, aluminates, and silicates. Manufacturing method. (6) The method according to claim (3), wherein the molten salt bath is a fluoride-containing molten salt bath. (7) The method according to claim (3), wherein the molten salt bath is a fluoride-containing halide bath. (8) The molten salt bath according to claim (3), wherein the molten salt bath is at least one molten salt bath selected from the group consisting of carbonates, phosphates, ferrates, aluminates, and silicates. Manufacturing method. (9) The production method according to any one of claims (3) to (8), wherein an immersion bath is prepared by adding a target metal or alloy and its oxide or halide to the molten salt bath.