JP3393758B2 - Tough cermet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cermet excellent in thermal shock resistance, fracture resistance and wear resistance, and particularly when used as a cutting tool material, intermittent cutting performance. Excellent TiC
It relates to N group cermet. [0002] In recent years, cutting tool materials, wear-resistant tool materials, and the like have been provided with a hard phase composed of double carbonitrides of elements of groups 4a, 5a and 6a of the periodic table and a bonded metal phase composed of iron group metals. The composed cermet is widely used. As such a cermet, there has been used TiC mainly composed of TiC.
Although the base cermet was the mainstream, the toughness was improved by adding nitride to this system because the toughness of this TiC-based cermet was inferior to that of cemented carbide used as a tool material for a long time. So-called TiCN-based cermets have been proposed. A typical example of the TiCN-based cermet is JP-B-56-5201.
i, W, Ta, Mo) CN and Ni, C
A cermet comprising a bonded metal phase consisting of o, a hard phase having a core portion rich in Ti or nitrogen, W, Ta,
It is stated to exhibit a cored structure composed of Mo and a carbon-rich periphery. Further, carbon (C) and nitrogen (N) forming a hard phase are major factors determining the toughness and hardness of a cermet. Recently, it has been attempted to increase the toughness of a cermet by adding a large amount of nitrogen. Attempts have been made to do so. [0005] Recently, however, improvements have been made to the above-mentioned TiCN-based cermet by further changing the structure of its surface to further increase wear resistance and toughness. For example, Japanese Patent Publication No. Sho 59-14534 discloses that a toughened softened layer is formed on the surface of a sintered body by introducing nitrogen into a furnace at a temperature lower than a liquid phase appearance temperature during firing. It has been proposed to form a layer having a higher hardness than the inside by firing in a reducing atmosphere containing CO. However, in these prior arts, only either hardness or toughness is examined, and cutting conditions such as operating temperature, atmosphere, and thermal shock become severe. It was becoming insufficient to obtain good cutting characteristics. In particular, as a problem related to thermal shock and mechanical shock, there has been a case where a blade edge is damaged and cannot be used. This is considered to be mainly because the conventional cermet is inferior in thermal shock resistance and fracture resistance as compared with cemented carbide. The inventor of the present invention has repeatedly studied the above problems, and has particularly studied methods for improving the thermal shock resistance and fracture resistance of cermets. By actively dissolving the Group 4a, 5a, and 6a metals of the periodic table of the hard phase component into the bonded metal phase composed of the group metal, the cermet has improved fracture resistance, thermal shock resistance, and abrasion resistance. Have been found to be able to be improved, leading to the present invention. That is, the tough cermet of the present invention is made of Ti
And at least one of carbides, nitrides, carbonitrides, and carbides, nitrides, and metals of Group 4a, 5a, and 6a metals of the periodic table excluding Ti.
70 to 95% by weight in total with one or more kinds selected from carbonitrides (excluding combinations of only carbides or only nitrides) and 5 to 30% by weight of iron group metal
Is a cermet obtained by firing a composition consisting of
A hard phase comprising a carbonitride of a Group 4a, 5a, or 6a metal and a binding metal phase containing an iron group metal, wherein in the binding metal phase, the periodic table 4a, 5a,
When 6a group metal is dissolved in a proportion of 10 to 40 atomic%
Both of the metals in groups 4a, 5a and 6a of the periodic table
In the ternary diagram of FIG. 1, the ratios by the atomic ratio are as follows: A, B, C, D It is characterized by being within the range surrounded by. DETAILED DESCRIPTION OF THE INVENTION toughness cermet of the present invention, the circumferential
Carbides, nitrides, charcoals of metals of Groups 4a, 5a, 6a of the Periodic Table
A hard phase consisting of nitride carbonitride and one of the iron group metals
And a binding metal phase containing two or more kinds. Also,
Cermets are composed of Ti carbides,
And at least one of carbides and carbonitrides and Periodic Table 4 excluding Ti
from carbides, nitrides and carbonitrides of metals from group a, 5a and 6a
One or two or more selected (but only carbide,
Or combinations of only nitrides are excluded. ) 70-
95% by weight, and 5 to 30% by weight of iron group metal.
Is obtained by firing a composition. In particular, it is desirable that the hard phase-forming component contains W, Ta, and Nb as essential components. Further, the composition according to the atomic ratio of the hard phase of the cermet is [(M
1) a (M2) b (M3) c] (CuNv) z (wherein M1 represents a Group 4a element, M2 represents a Group 5a element, and M3 represents a Group 6a element). 0.75 ≦ a ≦ 0.95 0.05 ≦ b + c ≦ 0.25 0 <b / (b + c) ≦ 0.95, a + b + c = 1 0.30 ≦ v ≦ 0.70, u + v = 1 0.80 ≦ z ≦ 1.0 is satisfied. In particular, M1 is mainly composed of Ti, and it is desirable that Ta is essential for M2 and W is essential for M3. Further, the amount of Ti in (M1) with respect to (a + b + c) is defined as 0.85 ≦ a as a
It is desirable that ≦ 0.92. In the above composition range, when a is smaller than 0.75 or (b + c) is larger than 0.25,
The sinterability is lowered, and the solid solution of the transition metal element in the binding metal phase is likely to be insufficient. When a is larger than 0.95 or (b + c) is smaller than 0.05, the improvement in fracture resistance is improved. I can not expect much. Also, b / (b + c) is 0.95
If it exceeds, the sinterability tends to decrease. The major feature of the cermet of the present invention is that the cermet is composed of the group 4a, the group 5a, or the group 6a in the whole bonded metal phase.
Group a metal content of 10 to 40 atomic%, especially 15 to 35 atomic%
And the amount of solid solution in a conventional general cermet (about 1 to
5 atomic%). If the amount of solid solution is less than 10 atomic%, solid solution strengthening becomes insufficient and sufficient fracture resistance cannot be obtained, and if it exceeds 40 atomic%, sinterability is reduced and fracture resistance is rapidly reduced. In particular, the solid solution forms group 4a and group 5a of the periodic table.
In the ternary diagram of FIG. 1, the following points A, B, C, D It is important to be within the range enclosed by. This is because if the content of Group 5a is less than 1 atomic%, the chipping resistance and wear resistance become insufficient, and if it exceeds 20 atomic%, the sinterability is reduced and the chipping resistance becomes particularly insufficient. is there. On the other hand, if the content of Group 4a exceeds 89 at%, sudden loss occurs, and if it is less than 60 at%, plastic deformation increases. On the other hand, the amount of nitrogen and the amount of carbon in the cermet are very important as factors that determine the mechanical and thermal characteristics of the cermet. In particular, as the amount of nitrogen increases, the fracture resistance improves. Group 4a, 5 to bonded metal phase
The amount of solid solution of Group a and Group 6a metals tends to increase,
When the amount of nitrogen is excessive, there arises a problem that sinterability is reduced due to a problem of wetting with a bonded metal phase during firing. Therefore, in the composition formula of the hard phase, if the nitrogen content (v) is smaller than 0.3, the fracture resistance becomes insufficient, and if it exceeds 0.7, voids are generated in the sintered body, resulting in poor reliability and solid solution. Insufficient reinforcement. Desirably, 0.4 ≦ v ≦ 0.6. If the ratio (z) of the amount of nitrogen and carbon to the total amount of M1, M2 and M3 is less than 0.8, the sinterability deteriorates and voids remain. As a result, the strength is reduced. Desirably, 0.85 ≦ z ≦ 1.0. In the present invention, examples of the iron group metal forming the bonding metal phase include Ni and / or Co, and are preferably composed of Ni and Co, and particularly Co / Ni + C
The molar ratio of o is preferably 0.5 to 0.9 from the viewpoint of improving the wear resistance. As a method for producing the cermet of the present invention, for example, first, the aforementioned Ti, W, T
a, Nb and other powders of carbides, nitrides, carbonitrides and iron group metal powders of elements of groups 4a, 5a and 6a of the periodic table are weighed and mixed so that the final sintered body has the above-mentioned ratio, and then pressed. After molding by molding means such as molding, extrusion molding, injection molding, etc., firing is performed. The firing is performed at a temperature of 1400 to 1800 ° C. in a vacuum or a reducing atmosphere. At any temperature during sintering, a gas such as N ₂ , CO, Ar,
Atmosphere adjustment may be performed by introducing 760 Torr. In particular, Group 4a, 5
In order to increase the amount of solid solution of group a and group 6a elements as described above, the amount of transition metal dissolved in the binding metal phase is controlled by maintaining the temperature around 1200 to 1400 ° C. The solid solution amount can be increased as the holding time is longer. Particularly, the range of 0.5 to 5 hours is appropriate. Instead of maintaining the temperature in the temperature range of 1200 to 1400 ° C., the temperature may be adjusted by slowly increasing the temperature at a rate of 15 ° C./min or less. Also, the amount of transition metal solid solution can be controlled by adjusting the amounts of carbon and nitrogen contained in the carbides, nitrides, and carbonitrides at the time of preparation. At the maximum firing temperature, in order to prevent the surface of the sintered body from being roughened, after firing in an atmosphere of nitrogen pressure of 1 to 100 torr before and for about 0.5 to 2 hours after reaching the firing temperature, It is preferable to hold in a vacuum for about 0.1 to 1 hour. Further, according to the present invention, for the purpose of improving the characteristics of the above-mentioned system, Zr, Hf, Cr, V and the like are further added with carbides, nitrides, carbonitrides and the like to improve the characteristics. Can be achieved. EXAMPLES As raw material powders, TiN, TiCN, WC, T
aC, NbC, Mo ₂ C, VC, Ni and Co were weighed and mixed so that the composition became the ratio shown in Table 1 using each powder, and then mixed.
Press-formed into a milling chip shape for SDKN1203 at a pressure of 1.5 ton / cm ² , placed in a vacuum furnace, and gradually heated at a nitrogen pressure of 20 torr to 1350 ° C.
The holding time was set as shown in Table 1, further held at the highest temperature for 1 to 2 hours, and returned to vacuum for the last 30 minutes, and then allowed to cool. Each of the obtained sintered bodies had a smooth and good surface. With respect to the obtained sintered body, the amount of Group 4a, 5a, or 6a metal dissolved in the binder metal phase was measured. In the measurement, after the sintered body was pulverized, only the binding metal phase was selectively dissolved with hydrochloric acid, and the solution was quantified by ICP emission spectroscopy. The results are shown in Table 1. Then, a cutting test was performed on each sample under the following cutting conditions, and the cutting performance was confirmed. The number of impacts up to fracture and the amount of flank wear were investigated and the results are shown in Table 1. (Intermittent test) Work material SCM440H Cutting speed 200 m / min Cutting depth 2 mm feed 0.26 mm / tooth (wear test) Work material S50C Cutting speed 250 m / min Cutting depth 2 mm feed 0.2 mm / tooth The cutting test results are shown in the table. 1 is shown. [Table 1] As is evident from the results in Table 1, samples having a solid solution amount of 10 to 40 at% in the binding metal phase and a solid solution ratio of each transition metal in the range of points A, B, C and D are shown. No. 1 to 7
In this case, the number of impacts up to the fracture resistance exceeded 1,000, and the wear amount was excellent at 0.15 mm or less. On the other hand, in Sample No. 12 in which the amount of the transition metal dissolved in the binding metal phase is more than 40 atomic%, the sinterability is poor, so that the fracture resistance and wear resistance are greatly deteriorated. In sample No. 11 having a solid solution amount of less than 10 atomic%, the primary boundary portion was abnormally worn. Further, even when the solid solution amount is in the range of 10 to 40 atomic%, the sample N which deviates from the range of points A, B, C and D
In the cases of o. 8, 9, and 10, none of the excellent fracture resistance and abrasion resistance like the products of the present invention were obtained. As described above in detail, the cermet of the present invention is capable of forming a solid solution of a large amount of transition metal in a binder metal phase at a specific ratio to thereby provide the cermet as a whole with a fracture resistance, a thermal shock resistance, Furthermore, as a result of being able to improve wear resistance, cutting characteristics such as chipping resistance and wear resistance can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a ternary diagram showing a solid solution amount of a Group 4a, 5a, or 6a metal in a binding metal phase.

Claims (1)

(57) [Claims 1] One or more of carbides, nitrides, and carbonitrides of Ti, and carbides, nitrides of metals of Groups 4a, 5a, and 6a of the periodic table excluding Ti; One or more selected from carbonitrides (excluding combinations of only carbides or only nitrides) in a total of 70 to 95% by weight, and an iron group metal in an amount of 5 to 30% by weight . By firing a composition consisting of a proportion
A cermet, comprising a hard phase composed of a carbonitride of a metal of Groups 4a, 5a and 6a of the periodic table and a binding metal phase containing an iron group metal; , 5a and 6a metals are dissolved in the solid solution at a ratio of 10 to 40 atomic%,
In the ternary diagram of FIG. 1, the following points A, B, C, D A tough cermet characterized by being within the range enclosed by.