JPH0413842A - Ticn-base cermet - Google Patents

Abstract

PURPOSE:To improve wear resistance and breaking resistance by selecting Nb and V instead of Mo and Ta as hard components in a cermet consisting of a hard phase and a binding phase. CONSTITUTION:This TiCN-base cermet is constituted of a hard phase composed essentially of Ti and containing W, Nb, and V and a binding phase consisting of iron group metal. The composition of the remainder of the whole composition of the above cermet from which the above iron group metal is subtracted is represented by [(Ti)a(Nb,V)b(W)c](Cu,Nv)z, where (a+b+c)=1, (a)=0.5 to 0.95, (b+c)=0.05 to 0.5, (b)/(b+c)=0.4 to 0.8, (v)=0.4 to 0.6, (z)=0.8 to 1, and (u+v)=1 are satisfied. Further, the contents of Mo and Ta are regulated to <=0.5wt.%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a TiCN-based cermet with excellent wear resistance and toughness, and particularly to a cermet suitable as a cutting tool.

(Prior art) In recent years, as sintered bodies for cutting, sintered bodies from the periodic table No. 1 Va, Va,
Cermets that are composed of a hard phase made of a double carbonitride of a Via group element and a binder phase made of an iron group metal have come into use.

Until now, the mainstream of such cermets has been TiC-based cermets whose main component is TiC;
Because the base cermet has inferior fracture resistance compared to cemented carbide, which has been used as a tool material for a long time, so-called Ti has improved toughness by adding nitrides to this system.
CN-based cermets have been proposed.

The hard phase in this TiCN-based cermet is Ti, W
In addition, carbides and nitrides such as Mo and Ta are added as hard phase forming components. Of these, Mo and Mo2C improve the wettability of the hard phase with the binder phase. Therefore, it is considered an essential component as a hard phase component. Furthermore, TaC improves the oxidation resistance of cermet and has the effect of suppressing the progress of crater wear when used as a cutting tool, so it has been regarded as an essential component from the point of view of practicality.

In addition, carbon (C) and nitrogen (N), which form the hard phase, are major factors that determine the toughness and hardness of cermets, and recently attempts have been made to increase the toughness of cermets by incorporating large amounts of nitrogen. is being done.

However, recently various improvements have been made to TiCN-based cermets, for example, in Japanese Patent Publication No. 633017,
For systems containing a large amount of nitrogen, Mo and Mo2C do not have the effect of improving wettability with the binder phase and inhibit sinterability, so Mo and Mo2C are not added, and TiN
A system in which a phase consisting of cermet is precipitated has been proposed, and it has also been proposed to add NbC as a hard component to improve the thermal shock resistance and oxidation resistance of cermet.

(Problems to be Solved by the Invention) However, according to these TiCN-based cermets, these technical improvements have not led to essential improvements in cermets, and up until now there has been no improvement in the quality of cemented carbide, which is the mainstream tool material. Deterioration of cutting properties still remains. Moreover, as cutting conditions tend to become stricter, tool materials with even higher properties are required.

Therefore, after various studies on the composition of conventional cermets, we found that when Mo or Mo2C is added to cermets that form a cored structure in their structure, Mo itself has a higher hardness, thermal conductivity, Young's modulus, and oxidation resistance than TiC. T in the characteristics such as
Because it is inferior to IC, it tends to have a particularly low wear resistance as a tool material.
It is considered that it is better not to add Mo as proposed in the above issue. However, according to the structure of Japanese Patent Publication No. 63-3017, the precipitation of the TiN phase has the problem that since the TiN phase itself has poor wettability with metal, the interface with the binder phase becomes a source of fracture and the strength deteriorates. ing.

On the other hand, the oxidation resistance effect of Ta has almost no effect on cermets containing a large amount of nitrogen, and on the contrary it inhibits sinterability, especially when Mo is not added to obtain a dense body. It has been found that the need to set the sintering temperature at a certain level causes grain growth of the sintered particles and reduces the wear resistance of the cermet.

(Means for Solving the Problems) Based on the above findings, the present inventors investigated the composition of a cermet that has excellent wear resistance, chipping resistance, and oxidation resistance. As a result, Ti is the metal component forming the hard phase.
, W is an essential component, and conventionally Mo and Ta have been added to it, but instead of these, Nb and V are selected and blended in specific ranges, and Mo in the system is
The inventors have discovered that a TiCN-based cermet with excellent cutting properties can be obtained by reducing the amount of Ta as much as possible, leading to the present invention.

That is, the present invention is directed to TiC which is composed of a hard phase containing Ti, W, Nb and
It is an N-based cermet, and the composition of other components excluding the iron group metal from the overall composition of the cermet is ((T i) a (
When expressed as Nb, V)b (W)c](CuNv)z,
a+b+c=1.0.50≦a≦0.95.0.05≦
b+c≦0.5.0.40≦b/b+c≦0.
80.0.40≦v≦0.60.0.80≦z≦1.0
, u+v=1, and the amounts of Mo and Ta are each 0.5% by weight or less.

Next, the reason for setting the ratio of each metal element in the above range in the TiCN-based cermet of the present invention will be described.

First, as a component forming a hard phase, Ti is approximately T
Although it exists in the sintered body as iCN, the amount of Ti (a)
If it is less than 0.5, the wear resistance and low affinity for metals, which are characteristics of cermet tools, will be insufficient.
If it exceeds 0.95, the fracture resistance will be poor. In addition,
It is particularly desirable that a be 0.70<a≦0.9.

In addition, Nb, ■, and W are auxiliary components that form a hard phase, and all have the effect of suppressing the grain growth of the cermet, forming a fine crystal structure and increasing the strength of the cermet.
It acts to increase toughness. Therefore, the total amount of these (b+
If c) is less than 0.05, fracture resistance will be insufficient,
If it is larger than 0.5, the wear resistance tends to be poor and the reactivity with the workpiece material tends to be high. Note that (b+c) value is 0
．． It is particularly desirable that 10≦b+c≦0.30.

Among these, W is an essential component in order to improve the wettability of the hard phase with the binder phase and increase the toughness as WC, but when the hard phase is composed of (Ti, W)CN However, there is a problem in that properties such as wear resistance, oxidation resistance, and chipping resistance do not reach a practical level. Therefore, carbides such as Mo and Ta have been used as essential components for the purpose of strengthening the hard phase and improving its properties, but as mentioned above, M Since it has inferior properties compared to TiCN, it actually deteriorates the properties of the cermet. In addition, sinterability is greatly influenced by the amount of binder phase in the system,
When the amount of the binder phase is the same, the addition of TaC reduces sinterability and requires high temperature firing, which increases the grain size of the crystals and deteriorates the wear resistance of the cermet.

On the other hand, since Nb itself has superior properties as a carbide compared to Mo2C, it contributes to improving the properties of cermets, and since it does not affect the sinterability, it improves the wear resistance of cermets. , it was found that oxidation resistance and fracture resistance can be improved. In addition, ① enhances the effect of adding Nb by forming a hard phase with Nb as VC, and particularly improves the resistance during high-speed cutting of cermet. Abrasion resistance can be greatly improved.

From this relationship, the ratio of the content of Nb and ■ (b) to the content of W, Nb, and V (b + c) (b / b + c
) is less than 0.4 in the above formula, the wear resistance and oxidation resistance are poor, and conversely, when it is larger than 0.8, the chipping resistance is reduced. Note that the atomic ratio of Nb/V is 1 to 10, particularly 1 to 5.
It is desirable that

On the other hand, the amount of nitrogen and carbon is a very important factor in determining the hardness and toughness of cermets. In particular, as the amount of nitrogen increases, the toughness tends to improve, but if the amount of nitrogen is excessive, A problem arises in that gas from the decomposition of nitrides remains in the sintered body in the voids.

Therefore, in the above formula, if the nitrogen content (V) is less than 0.4, the toughness will decrease and fracture resistance will be insufficient, and if it exceeds 0.6, voids will occur in the sintered body and reliability will be lost. Become.

Furthermore, if the ratio (z) of the amount of nitrogen and carbon to the total amount of Ti, W, Nb, and This results in strength deterioration. Preferably 0.
85≦z≦1.0.

In the present invention, the iron group metal forming the binder phase includes N
i and/or Co, preferably Ni and C
Especially when the molar ratio of Co/Ni+Co is 0.
5 to 0.9 is good from the viewpoint of improving wear resistance.

Further, it is desirable that the iron group metal is present in the system in an amount of 3 to 30% by weight, particularly 5 to 20% by weight.

The cermet of the present invention includes Ti, W, Nb,
The carbides, nitrides, carbonitride powders and iron group metal powders are weighed and mixed so that the final sintered body has the above-mentioned proportions, and then molded by a molding means such as press molding, extrusion molding, or injection molding. It can be obtained by firing at a temperature of 1400 to 1600°C in vacuum, nitrogen atmosphere or reducing atmosphere.

Note that sinterability may decrease slightly due to suppressing the amount of Mo, which has excellent wettability with iron group metals during firing, but in this case, increase the amount of iron group metals or increase carbon Sinterability is improved by adding approximately 0.05 to 3% by weight of.

Furthermore, as the Ti compound-based raw material powder used, Tic,
TiCN, TiN, etc. may be mentioned. In some cases, TiN may remain in the final sintered body as a TiN phase, but since this TiN phase itself has poor wettability with the binder phase, the binder phase and Ti -IO- The interface with the N phase becomes the starting point of the crank and deteriorates the mechanical properties of the cermet. Therefore, Tic as a raw material
or TiCN, without adding a large amount of TiN powder,
Care should be taken to ensure that no TiN phase is formed.

According to the present invention, carbides, nitrides, carbonitrides, etc. such as Zr, Hf, Cr, etc. can be further added to the above system for the purpose of improving the characteristics.

The invention will now be explained with the following examples.

(Example) TiC, T with an average particle size of 1 to 1.5 μm as raw material powder
i CN, WC, NbC1VC, Ni and Co powders were weighed and mixed so that the composition of the final sintered body would be in the proportions shown in Table 1, and then TN was heated at a pressure of 1.5 ton/cm2.
It was press-molded into a chip shape for GA160408. In addition, in the first table, sample No.

No. 17 is a system containing only Nb and no V, and No. 18 is a system containing only ■ and no Nb. Next, these molded bodies were
It was baked at a temperature of 00 to 1600°C in a vacuum atmosphere for 1 hour. When the structure of the obtained sintered body was observed,
It was composed of a hard phase consisting of double carbonitrides of Ti, W, Nb, and ■ and a binder phase, and no precipitation of the TiN phase was observed.

These sintered bodies were measured for three-point bending strength, Vickers hardness, and fracture toughness by the indentation method using a diamond indenter for Vickers hardness at a load of 20 kg in accordance with JISR1601.

Next, each sample was subjected to an abrasion test under the cutting conditions shown below.
A chipping test was conducted to examine the amount of flank wear after cutting and the number of non- chipping corners.

(Wear test) Work material cutting speed Depth of cut Feed Cutting time (Defect test) Work material cutting speed Depth of cut 30M435 (4 grooves) 100m/min mm CM435 200m/min mm 0.3mm/rev 0m1n 12 = Feed 0. 3 mm/rev cutting time 1 m1n The results are shown in Table 2. (Comparative Example 1) 2% by weight of Ni, 8% by weight of Co, and other components (Ti
o, 5iWo, o5M o o, to) (Co, 5
sNo., 45) o, q.

Sample No. 019 was obtained by firing in the same manner as in the example except that the mixture was weighed and mixed so as to have a composition consisting of the following. The properties of the obtained sintered body were measured in the same manner as in the examples. The results are shown in Table 2.

(Comparative Example 2) 2% by weight of Ni, 8% by weight of Co, and other components (T i
o, g5Wo, osTao, to) (Co, 55No,
ai) Sample No. 20 was obtained by firing in the same manner as in the example except that the mixture was weighed and mixed so as to have a composition of 0.9°.

The properties of this sintered body were measured in the same manner as in the examples.

The results are shown in Table 2.

(Hereinafter, blank space) According to Tables 1 and 2, the hard phase fracture resistance has conventionally been inferior to that of the products of the present invention.

On the other hand, all the samples of the present invention show excellent cutting performance, but all the samples whose compositions of Ti, W, Nb, C, and H deviate from the range of the present invention yielded satisfactory results. I couldn't.

(Effects of the Invention) As detailed above, the TiCN-based cermet of the present invention exhibits excellent wear resistance and chipping resistance by selecting Nb and V instead of Mo and Ta as hard phase components, It can be used as a tool material to extend its life.

Claims (2)

[Claims] (1) Ti consisting of a hard phase mainly composed of Ti and containing W, Nb and V, and a binder phase consisting of an iron group metal.
It is a CN-based cermet, and the other component composition excluding the iron group metal and unavoidable impurities from the overall composition of the cermet is [(Ti)_a(Nb,V)_b(W)_c](C_
When expressed as uN_v)_z, a+b+c=1, 0.50
≦a≦0.95, 0.05≦b+c≦0.5, 0.40
≦b/b+c≦0.80, 0.40≦v≦0.60, 0
．． While satisfying 80≦z≦1.0, u+v=1,
A TiCN-based cermet characterized in that the amounts of Mo and Ta are each 0.5% by weight or less. (2) The atomic ratio of Nb and V (Nb/V) is 1 to 10
The TiCN-based cermet according to claim (1), which falls within the range of .