JPH06228701A - Silver-colored sintered alloy and its production - Google Patents

Abstract

PURPOSE:To produce a silver-colored sintered alloy remarkably excellent in hardness, strength, and corrosion resistance, having smoothness and superior wear resistance and sliding characteristic, and producing a dark-silver-colored mirror-like surface. CONSTITUTION:This alloy is a silver-colored sintered alloy where titanium carbide is used as grain phase to be dispersed and also chromium, molybdenum, and nickel are used as binding phase. This alloy contains, by weight, chromium by 1-15% expressed in terms of carbide based on the total, molybdenum by 3-32% expressed in terms of carbide based on the total, and nickel by 1-20% based on the total. Further, the porosity specified by ANSI/ASTM B276-54 is higher than A-2 class in this alloy. This alloy can be obtained by sintering a powder mixture composed essentially of titanium carbide and containing, by weight, 1-15% chromium carbide, 1-10% molybdenum carbide, 1-20% nickel, and 0.5-15% molybdenum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to titanium carbide (TiC).
The present invention relates to a silver-colored sintered alloy containing as a main component.

[0002]

2. Description of the Related Art Recently, TiC is a main component, and Fe, Co,
Sintered alloys containing binding metals such as Ni, Mo, W, and Ti have excellent properties in hardness and strength in addition to the silver color tone, so they are widely used as wear-resistant materials and decoration materials. Has been done.

However, it is very difficult to sinter TiC itself, and the above-mentioned binding metal is added as a sintering aid in order to obtain a high-strength sintered body.

[0004]

However, since these sintering aids are metallic elements, the corrosion of the metal components present in the sintered alloy progresses, for example, they corrode or discolor due to sweat, etc. Then, there has been a problem that the characteristics and color tone of the wear resistant member or the decorative member are impaired. Moreover, the sintering aids, especially iron group metals, do not yet have satisfactory wettability with TiC, many voids appear throughout the crystal and grain boundaries, and smooth and deep mirror surface even after mirror polishing. However, there was a drawback that it did not appear. In addition, the voids accelerate the progress of corrosion.

[0005]

In view of the above circumstances, the inventors of the present invention have made earnest studies, and as a result, selected chromium carbide and molybdenum carbide among various carbides and nickel and molybdenum among various metal elements. It has been found that when a combination of the above components with titanium carbide in a limited amount is sintered and this is sintered, a hard silver-colored sintered alloy having excellent wear resistance, in which the above-mentioned conventional determination is eliminated, is obtained.

The present invention has been completed on the basis of the above findings, and its purpose is to have a significantly excellent corrosion resistance, smoothness, wear resistance and slidability, and a deep silver mirror surface. It is an object of the present invention to provide a developed silver-colored sintered alloy having excellent wear resistance and a method for producing the same.

That is, the sintered alloy of the present invention is a silver-colored sintered alloy having titanium carbide as a dispersed particle phase and chromium, molybdenum, and nickel as a binder phase. ˜15% by weight, 3 to 32% by weight of the molybdenum in terms of carbide in the total amount, and 1 to 20% by weight of nickel in the total amount, and ANSI / AS.
A silver-colored sintered alloy having a porosity defined by TM B276-54 of A-2 class or higher. Such a silver-colored sintered alloy contains titanium carbide as a main component, 1 to 15% by weight of chromium carbide, 1 to 10% by weight of molybdenum carbide, 1 to 20% by weight of nickel, and 0.5 to 5% of molybdenum.
It is formed by firing a mixed powder of 15% by weight.

The sintered alloy according to the present invention is also made of titanium carbide (Ti
It is the same as the conventional one in that C) is the main component, but chromium carbide and molybdenum carbide are selected among the carbides, and nickel (Ni) and molybdenum (Mo) are selected among the binding metals and fired. It will be done. Then, in a five-component composition ratio, chromium carbide in the carbide is 1 to 15% by weight, particularly preferably 3 to 10% by weight, molybdenum carbide is 1 to 10% by weight, particularly preferably 3 to 7. 5% by weight and 1% nickel in the binder metal
To 20% by weight, particularly preferably 5 to 15% by weight,
Blending molybdenum in an amount of 0.5 to 15% by weight, particularly preferably 1 to 10% by weight is a remarkable feature over the prior art.

The sintered alloy of the present invention has a fine structure. This is easily confirmed by subjecting it to analysis by an X-ray microanalyzer.

That is, according to the sintered alloy of the present invention, titanium carbide exists as a dispersed particle phase, and nickel metal and molybdenum metal form a grain boundary phase as a binding phase. The titanium carbide dispersed particles have a size of 1 to 3 μm. In addition, chromium carbide (Cr ₃ C ₂ ) and molybdenum carbide (Mo
_{For 2} C), all the chromium and molybdenum atoms are replaced with the nickel and molybdenum atoms in the nickel-molybdenum metal crystal in the bonding phase, and all the carbon atoms are incorporated into the nickel-molybdenum metal crystal to form a solid solution. To form. Incorporation of carbon atoms into the nickel-molybdenum metal crystal in this way lowers the melting point of the nickel-molybdenum bonding phase, which can lower the sintering temperature.

In the sintered alloy of the present invention, pores and voids are remarkably reduced because of the above-mentioned fine structure and the like.
It is considered that this is because the wettability of the nickel-molybdenum binder phase was improved and the sintering temperature was lowered.

As the chromium carbide, one having a composition of Cr ₃ C ₂ is generally used, and this one is preferably used, but in addition, a composition having a composition of Cr ₇ C ₃ or Cr ₂₃ C ₆ is used alone or Used in combination.

Further, according to the present invention, it is important to use the above-mentioned 5 components in a specific amount ratio. That is, when the content of chromium carbide is less than 1% by weight, the wettability with respect to TiC is not improved and the corrosion resistance is not improved so much.
This is because if the amount exceeds 5% by weight, a sintered product with a strong reddish color is formed, which is unsuitable as a silver decorative member. If the blending amount of molybdenum carbide is less than 1% by weight, the sinterability is not improved.
Even if it exceeds 0% by weight, the sinterability deteriorates. Further, the reason for specifying the blending amount of nickel is that if the blending amount is less than 1% by weight, the sinterability is reduced and a dense sintered body cannot be obtained, and the strength is remarkably lowered, and if it exceeds 20% by weight. This is because the corrosion resistance decreases. The reason for specifying the compounding amount of molybdenum is that if it is less than 0.5% by weight, the efficiency of suppressing carbon precipitation is lost, and a dense sintered body cannot be obtained, and if it exceeds 15% by weight, the hardness is significantly reduced due to the generation of a metal pool. To do. Further, the main component, titanium carbide, must be contained in the sintered body in an amount of 50% by weight or more, and if it is less than 50% by weight, a hard silver-colored sintered body cannot be obtained. It is good to have been.

Further, in the composition of the sintered body, the content of chromium in the total amount of 1 to 15% by weight calculated as carbide is 1
If it is less than 15% by weight, the wettability with respect to TiC is not improved and the corrosion resistance is not so much improved, and if it exceeds 15% by weight, a sintered product with a strong reddish color is obtained. 3 to 32% by weight of molybdenum converted to carbides in the total amount was 3
This is because if it is less than wt% or exceeds 32 wt%, the sinterability deteriorates. Nickel is contained in an amount of 1 to 20% by weight based on the whole amount because if it is less than 1% by weight, the sinterability is lowered and a dense sintered body cannot be obtained, and if it exceeds 20% by weight, the corrosion resistance is lowered. Is. And ANSI / ASTM B27
The amount of deposited carbon specified by 6-54 is set to A-2 class or more because a deep silvery mirror surface does not appear when the deposited carbon amount is lower than the A-2 class.

The sintered alloy of the present invention contains the above-mentioned five components as essential, but does not exclude the inclusion of other components. For example, a portion of chromium carbide may be replaced with some other carbide, such as niobium carbide, and a portion of metallic nickel may be replaced with another binding metal, such as cobalt.

The particle sizes of titanium carbide raw material powder, chromium carbide raw material powder, molybdenum carbide raw material powder, and nickel and molybdenum metal powders are all 3.0.
It may be less than or equal to μm, preferably less than or equal to 1.0 μm.

In the method for producing a sintered alloy of the present invention, chromium carbide and molybdenum carbide and nickel and molybdenum are added to titanium carbide raw material powder, the mixture is uniformly mixed, and the mixture is pressure-molded and fired. This firing is performed in a non-oxidizing atmosphere furnace such as nitrogen or argon or in a vacuum furnace (vacuum 10 ^{-2 to} 10 ^-5 Tor).
When the process is carried out in r) in the temperature range of 1300 to 1500 ° C., a hard silver-colored sintered alloy having excellent corrosion resistance and having a smooth and deep mirror surface can be obtained.

[0018]

In the sintered alloy of the present invention, the binding metal nickel is melted and the sintering proceeds, but titanium carbide contains many pores in the sintered body produced due to poor wetting by the molten metal. However, as a result of the depressions on the mirror surface, the surface is not smooth, and the luster is dull, and it tends to become dull. In addition, the local battery action between the binding metal and the titanium carbide particles causes a drawback that metal corrosion easily progresses.

The chromium carbide and molybdenum carbide used in the present invention act to remarkably improve the wettability of the titanium carbide particle surface with the molten metal, and react with the molten metal to provide corrosion resistance in the bonded metal phase. It acts to form a good nickel-chromium-molybdenum composite alloy.
Therefore, according to the present invention, it is possible to form a sintered body having extremely few pores, it is possible to form a deep mirror surface with a smooth surface, and the corrosion resistance of the sintered body is significantly improved. Of. From the viewpoint of forming the nickel-chromium-molybdenum composite alloy phase, it is also extremely important to use nickel and molybdenum as the binding metal.

Further, the molybdenum metal is important because it contributes to the suppression of free carbon precipitated by the reaction of titanium carbide with carbides of chromium and molybdenum.

Examples of the present invention will be described below.

[0022]

[Examples] Raw material powders were mixed in the ratios shown in Table 1 and I
The mixture was mixed and ground in PA for about 68 hours. After this was dried, 4% by weight of paraffin was added and pressure-molded at 1.5 ton / cm ² , and after debinding, firing temperature of 1350 ° C. and 10
Vacuum firing was performed for 1 hour at a vacuum degree of ^-3 torr.

The sintered alloy thus obtained is mirror-polished,
Its color tone, mirror state, bending strength, Vickers hardness (H
v) and corrosion resistance were investigated.

The bending strength was measured according to JIS-R-1601 three-point bending test method, and the Vickers hardness (Hv) was measured according to JIS-Z-2244 test method. As for the corrosion resistance test, the sweat resistance test and salt water (4 wt%
/ Vol) was sprayed and sprayed with salt water (JIS-Z-2371). In addition, the mirror surface state is a void level and (A
The amount of precipitated carbon specified by NSI / ASTM is A-2.
The results are shown in Table 2.

[0025]

[Table 1]

[0026]

[Table 2]

The results of the corrosion resistance test in Table 2 are as follows.
The same results were obtained in both the sweat resistance test and the salt spray test, and the ○ mark indicates that there is no discoloration or corrosion, and the color tone is not deteriorated at all, and the △ mark indicates that there is discoloration. The symbol X indicates that corrosion was observed in addition to discoloration, and the color tone gradually deteriorated, which means that the product was unsuitable as a decorative member.
Regarding the results of the mirror surface state, the porosity due to the amount of precipitated carbon etc. is defined by ANSI / ASTM B276-54, A-6 class, B-1 to B-6 class and C-class.
Those of 1 to C-6 class are marked with X, those of A-3 to A-5 class are marked with Δ, and those of A-2 class and above are marked with ◯.
It is shown that if the pore level is A-2 class or higher, it can be provided as an excellent material having no trouble as a decorative member and a wear resistant member.

As is clear from Tables 1 and 2, the results of the corrosion resistance test show that Sample Nos. 3 to 7 and 10 to 16 are excellent in silver-colored decorative members having no discoloration and corrosion and no color deterioration. . In addition, it can be seen that the bending strength and hardness also show practically suitable characteristic values.

However, sample numbers 1 and 9 in which Cr ₃ C ₂ is out of the setting range of the present invention, and sample numbers 8 and 19 in which Mo ₂ C is out of the setting range of the present invention or Ni.
Is sample number 17 out of the setting range of the present invention, and M
Regarding Sample Nos. 1, 2, and 18 in which o was out of the setting range of the present invention, the hardness was remarkably lowered. As described above, when the value deviates from the set range of the present invention, the hardness and strength are lowered, or a sintered body having excellent corrosion resistance and the appearance of a deep silver mirror surface cannot be obtained.

[0030]

INDUSTRIAL APPLICABILITY As described above, the silver-colored sintered alloy of the present invention exhibits excellent strength and hardness without any problems in decorative applications and wear resistance applications, and has excellent corrosion resistance and deep silver color. The mirror surface appears, and as a result, by maintaining the decorative effect and wear resistance for a long period of time, it can be used for decoration materials such as wall materials, watch cases, brooches, commemorative medals, buttons, bracelets, rings, pendants, fishing tackle, and wear resistance. Awarded as a wear member.

Claims (2)

[Claims] 1. A silver-colored sintered alloy having titanium carbide as a dispersed particle phase and chromium, molybdenum, and nickel as a binder phase, wherein 1 to 15% by weight of the chromium is converted into carbide in the total amount of the molybdenum. 3 to 32 converted to carbides in the total amount
%, And 1 to 20% by weight of the nickel in the total amount, and a porosity defined by ANSI / ASTM B276-54 is A-2 class or more, a silver-colored sintered alloy. 2. Titanium carbide as a main component, chromium carbide 1 to
A method for producing a silver-colored sintered alloy, which comprises firing a mixed powder of 15% by weight, 1 to 10% by weight of molybdenum carbide, 1 to 20% by weight of nickel, and 0.5 to 15% by weight of molybdenum.