JPS5952224B2 - Sintered hard alloy parts with nitrided surface layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered hard metal member having a nitrided surface layer, which has various color tones, has excellent wear resistance and corrosion resistance, and is particularly suitable for use as a decoration. It is something.

Generally, sintered hard alloys containing carbides, nitrides, or carbonitrides of transition metals in Groups 4a, 5a, and 6a of the periodic table as main components have high hardness and excellent toughness. For this reason, it is used as various cutting tools and wear-resistant tools, and it is also used for decorative purposes because its polished surface is beautiful and is relatively hard to scratch.

In particular, sintered hard alloys containing tantalum carbide (Tac) as a main component are known as valuable decorative materials because of their deep lemon-gold color, and they also contain titanium nitride (TiN) as a main component. It is also known that sintered hard alloys exhibit an orange-gold color. However, these fired hard alloys not only provide a wide variety of color tones, but also, for example, fired hard alloys containing nitrides as a main component contain a large amount of nitrides. Due to this, both sinterability and polishability during production are poor, and if a large amount of nitride is contained, a product with high strength cannot be obtained.

Also, transition metals of groups 4a and 5a of the periodic table, especially T
Since i has the property of being easily nitrided, a method has been proposed in which the surface of the Ti alloy is nitrided, but the resulting Ti alloy member with a nitrided surface layer has a relatively low base material hardness. Not only is the nitrided surface layer thin, there is a problem that it is easily scratched by contact with hard objects. In this case, it is impossible to avoid the occurrence of significant unevenness on the surface, and from this point of view, it is not suitable for use as a decoration.

Furthermore, titanium (TiN) and hafnium nitride (
A surface-coated sintered hard alloy member coated with HfN has also been proposed, but in this case, a coating process and dedicated equipment are required, which inevitably increases costs. From the above-mentioned viewpoint, the present inventors focused on a sintered hard alloy member containing carbide, which can form a nitrided surface layer without the need for special equipment, and has a variety of color tones. As a result of our research to obtain a sintered hard alloy member that is resistant to scratches and does not cause unevenness on the nitrided surface layer, we found that the carbide-containing sintered hard alloy part contains transition metals from groups 4a and 5a of the periodic table. When one or more of these nitrides are contained, roughness (unevenness) of the nitrided surface layer is prevented, and when one or two of chromium carbide and tungsten carbide are contained, the strength is improved. This makes it less likely to be scratched and improves corrosion resistance.Furthermore, the carbide contained above is one of the carbides of transition metals in groups 4a and 5a of the periodic table.
They have found that when the material is composed of one species or two or more species, desired color development can be ensured through nitriding during sintering.

Therefore, this invention was made based on the above knowledge, and contains MO as necessary, one or two of CO and Ni: 3 to 30%, carbonized as necessary. One or two of chromium (hereinafter referred to as Cr3c2) and tundaste carbide (hereinafter referred to as WC):
0.1 to 20%, one or more nitrides of transition metals in groups 4a and 5a of the periodic table (hereinafter abbreviated as transition metal nitrides): 25 to 50%, also in the periodic table One of the carbides of transition metals of groups 4a and 5a in Table
species or two or more species (hereinafter abbreviated as transition metal carbide)
and unavoidable impurities: 30-65%, (more than % by weight)
), and is characterized by a sintered hard alloy member having a nitrided surface layer on its surface. Next, the reason why the composition range of the sintered hard metal member of the present invention is limited as described above will be explained.

(a) MO, CO and Ni CO and Ni are contained as bond phase components, and M
O is a component that is included as necessary when sinterability is particularly required, but if its content is less than 3%, it will not be possible to sufficiently wet the hard phase during sintering, resulting in poor sintering. Since the aggregates are not completely densified, the strength decreases significantly; on the other hand, 3
If the content exceeds 0%, the hardness decreases, the scratch-proof property is lost, and the color tone becomes whitish and monotonous, so the content was set at 3 to 30%.

(b) Cr3C2 and WC These components have the effect of improving strength and corrosion resistance, so they are included depending on the requirements when these properties are required, but the content is 0.1%. If the content is less than 20%, the desired effect cannot be obtained; on the other hand, if the content exceeds 20%, the sinterability will decrease and the relative content of transition metal nitrides and carbides that form a colored hard phase will decrease. Since the amount decreases and a richly varied color tone cannot be obtained, the content is set at 0.1 to 20%.

(6) Nitride of transition metals These components have the effect of preventing roughening of the nitrided surface layer, but if the content is less than 25%, the desired effect cannot be obtained, and if the content exceeds 50%, If it is contained, the sinterability will deteriorate and a sufficiently dense sintered body cannot be obtained, so the content is set at 25 to 50%.

(6) Transition metal carbide These components have the effect of being nitrided during sintering and developing color, but if their content is less than 30%, the color tone will be too large compared to the base material color tone due to the coloring effect. On the other hand, if the content exceeds 65%, the relative amount of the hard phase becomes too large and the strength decreases, so the content was set at 30 to 65%.

In the production of the sintered hard alloy member of the present invention, the transition metal nitride may be incorporated by using a trowel using the transition metal nitride powder alone as the raw material powder, or by using the above-mentioned method. A solid solution powder of nitride and one or more of Cr3c2, WC, and transition metal carbides may be used as a raw material powder, but it is better to use the latter form for better sinterability. and has good polishability.

The nitrided surface layer is formed by sintering in a nitrogen atmosphere under reduced or pressurized conditions, preferably at a temperature at which the gas adsorbed on the press-formed compact is sufficiently removed. It is preferable to create a vacuum atmosphere and then sinter in a nitrogen stream or nitrogen atmosphere. In this case, the same result can also be obtained by re-sintering the sintered body that has been vacuum-sintered in a nitrogen atmosphere. Furthermore, the thickness of the nitrided surface layer is determined by the component composition, the pressure of the nitriding atmosphere, the sintering temperature, the sintering time, etc., so it can be selected appropriately according to the predetermined conditions, and the resulting nitrided surface layer is Not only does it have a strong bond with the base material, but it also has a smooth surface, so it can be used with the sintered skin as it is, or with a light wrapping that does not remove the nitrided surface layer.
Next, the sintered hard metal member of the present invention will be explained with reference to Examples.

Example raw material powders include Ni powder with an average particle size of 1.5 μm, CO powder with an average particle size of 1.2 μm (7), and M with an average particle size of 1.3 μm (7).
O powder, 1.5 μm (7) Cr3C2 powder, 1.2
μm (7) WC powder, both 1.3 μm (Ti,
W) CN powder (TiC/TiN/WC=40/50/1
0, weight ratio (same below), (Ti, Nb)CN powder (
TiN/Nbc=60/40), TiCN powder (TiC
/TiN=50/50), and (Ti,Ta)CN powder (TiN/TaC=70/30), the same 1.8 μm (
Ta, Nb)・CN powder (TaN/TaC/NbC=2
0/70/10), both of which have the same 1.5 μm
N powder, HfN powder, NbN powder, and VN powder, as well as ZrC powder and HfC powder, all of which have the same diameter of 1.3 μm.
Powder and VC powder were prepared, and these raw material powders were blended into the composition shown in Table 1, wet mixed in a ball mill according to the usual powder metallurgy method, dried, and compressed by press molding. A powder is formed, and then this green compact is heated in a vacuum atmosphere at a temperature up to 1300°C for 1 time.
The temperature range from 300°C to a predetermined sintering temperature in the range of 1450 to 1550°C is heated in a sealed nitrogen atmosphere at a predetermined pressure in the range of 100 to 600t0rI', and the sintering temperature is maintained for 1 hour. Therefore, sintered hard alloy members 1 to 10 of the present invention having substantially the same composition as the blended composition and each having a nitrided surface layer with a thickness and a sintered skin with a color tone shown in Table 1 are used. Manufactured.

The sintered hard alloy members 1 to 10 of the present invention obtained as a result are as follows:
All of them have beautiful sintered skins with very little unevenness, and as shown in Table 1, their rich color tones make them extremely useful for decorative purposes.

Claims (1)

[Claims] 1 One or two of Co and Ni: 3 to 30
%, one or more nitrides of transition metals of groups 4a and 5a of the periodic table: 25-50%, 4 of the periodic table
It has a composition (in weight percent) of one or more carbides of transition metals of groups A and 5a and unavoidable impurities: 30 to 65%, and has a nitrided layer on the surface. A sintered hard alloy member with a nitrided surface layer. 2 One or two of Co and Ni and Mo3~
30%, one or more nitrides of transition metals from groups 4a and 5a of the periodic table: 25-50%, one carbide of transition metals from groups 4a and 5a of the periodic table A sintered hard metal member having a nitrided surface, characterized in that it has a composition (weight %) of two or more types and unavoidable impurities: 30 to 65%, and has a nitrided layer on the surface. 3 One or two of Co and Ni: 3 to 30
%, one or two of chromium carbide and tungsten carbide: 0.1 to 20%, 4a and 5a of the periodic table
One or more of the group transition metal nitrides: 2
5 to 50%, one or more nitrides of transition metals in groups 4a and 5a of the periodic table: 25 to 50%, carbides of transition metals in groups 4a and 5a of the periodic table A sintered hard alloy member having a nitrided surface layer, having a composition (weight %) of one or more types and unavoidable impurities: 30 to 65%, and having a nitrided layer on the surface portion. 4 One or two of Co and Ni and Mo: 3
~30%, one or two of chromium carbide and tungsten carbide: 0.1 to 20%, one or more of nitrides of transition metals of groups 4a and 5a of the periodic table: 25 ~50%, one or more carbides of transition metals of Groups 4a and 5a of the periodic table, and 30~65% of unavoidable impurities (weight%),
A sintered hard alloy member having a nitrided surface layer, characterized in that the surface portion has a nitrided layer.