JPH0611897B2 - High strength sintered alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-strength sintered alloy having excellent toughness, wear resistance, and high-temperature strength suitable for wear-resistant tool parts or cutting tool parts.

(Prior art) WC-based sintered alloy, which is the most familiar as a sintered alloy for wear-resistant tools or cutting tools, has its hard phase, WC itself, which is comparatively melted into steel, which is the most commonly used work material. Due to the property of being easy, it has a drawback that so-called crater wear is large in cutting steel.

As one means to improve this drawback, TiC-based sintered alloys have appeared instead of WC-based sintered alloys. The most typical TiC-based sintered alloy is represented by the TiC-Mo ₂ C-Ni component system, but the most characteristic point in the structure of this system is that the hard phase is TiC particles. Is a core part, and a solid solution of TiC and Mo ₂ C is an outer peripheral part. The presence of the outer peripheral portion significantly improves the wettability with the binder phase and maintains the strength of the entire alloy. In this way Ti
C-based sintered alloys have been evaluated as useful tool materials in the field of steel cutting, but they remain problematic in strength due to plastic deformation at high temperatures, and they are also unsatisfactory in wear resistance at high temperatures. It was

The addition of nitrogen to TiC-based sintered alloys has been very successful at present as a solution to the above problems. That is,
As a means for adding nitrogen, a small amount of TiN or TiCN having a small nitrogen content is added to serve as a nitrogen source, TiC or TiCN particles are used as the core, and a solid solution composed of Ti, Mo, C, N is used as the outer circumference. Many cermets have been proposed.

(Problems to be Solved by the Invention) As the effect of nitrogen addition becomes apparent, it is natural to consider increasing the amount of nitrogen addition to further increase the effect, but Ti (C, N) For example, when Ti (Co. ₂ No. ₈ ) or extremely large amount of TiN is added, these particles have extremely poor wettability with the binder phase, resulting in burrows and uneven sintering in the alloy. Occurs, resulting in a significant decrease in the strength of the entire alloy.

To resolve this problem is to the same solid solution and formed around the TiC particles may if formed as the outer peripheral portion of the TiN or _{Ti (Co. 2 No. 8)} , for example, Ti (C _1-X N _{In the (X} ) -Ni-Mo alloy, when the value of x is 0.7 or more, no peripheral structure is formed on the surface of Ti (C, N) grains (Powder Metallurgy International, vol.14, No4, 1982). )
And, also in the _{TiC-TiN-Mo 2 C-} Ni engagement alloy, not occur at all the outer peripheral part tissue on the surface of the TiN particles (Powder and Powder Metallurgy, 23 (1976), 224) is today because It is a myth.

Despite such a myth, the present inventors conducted extensive research to form an outer peripheral structure having good wettability with the binder phase also on the surface of TiN, and the present invention was guided by the following idea. It came to completion.

Originally, in the TiC-TiN-Mo ₂ C-Ni alloy, the outer peripheral part formed on the surface of TiC particles is melted into the liquid phase from each of TiC, TiN, and Mo ₂ C particles, and then to the surface of TiC particles. It is said that a so-called melt-protrusion mechanism is used in which the protrusions are formed by repeating this process.

This is a fact that has been confirmed by many experiments, but in fact, in addition to the reaction of dissolution protrusion, the diffusion of the liquid phase component to each particle simultaneously progresses through the interface between each particle and the liquid phase. It should be. In particular, in TiN grains that do not have a peripheral portion, nitrogen diffuses from the liquid phase, and Ti near the surface
(C, N) is generated. Under the conventional sintering conditions, the latter of these two phenomena, diffusion and dissolution protrusion, occurs predominantly, so the Ti (C, N) layer formed on the surface of TiN dissolves without growing. It is thought to have gone away. Therefore, if this balance can be changed by appropriate selection of sintering conditions, a Ti (C, N) layer is formed by the diffusion of carbon near the surface of the TiN particles, and in particular, it is Ti (Co. Once the ₇ No. ₃₎ having a low nitrogen concentration as issues wettability good solid solution peripheral portion tissue folding of the binder phase in the surface strength of the alloy should be markedly improved.

The present invention, the problem as described above, around TiN remaining in the TiC-based sintered alloy, Ti, Zr, Hf, V, Nb, Ta, Cr, which has better wettability with the binder phase than TiN, The problem is solved by forming the outer peripheral portion of a carbonitride solid solution containing two or more kinds of Mo and w, and in addition to the excellent property of TiN, that is, the grain growth suppression effect, the affinity with steel and It embodies a low coefficient of friction, high thermal conductivity, high toughness, etc., resulting in high-strength, heat-resistant plastic deformation, welding resistance, and wear resistance. The purpose is to provide bond money.

(Means for Solving Problems) In the TiC-based sintered alloy containing TiN,
In particular, the higher the nitrogen content, the more TiN remains in the sintered alloy, and the poor wettability of this TiN with the binder phase of Co and / or Ni causes uneven sintering and porosity, resulting in a marked decrease in strength. As a result of studying the crystal structure of the alloy that solves the problem and further maximizes the effect of TiN described above, the following first, second and third findings are obtained.

The first finding is that titanium carbide and titanium nitride as starting raw material powders and carbides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, w and Zr, Hf,
At least one of V, Nb, Ta, Cr, Mo, w nitrides and their mutual solid solutions of carbides and nitrides, and Co and / or Ni are used and treated by powder metallurgy and sintered, By controlling the particle size of the starting raw material powder and controlling the sintering conditions, a cored hard phase consisting of the core of TiN and the outer periphery of the carbonitride solid solution surrounding the core is formed, and this cored hard phase is If it occurs in the sintered alloy, the occurrence of uneven sintering and voids should be eliminated, and the life of the sintered alloy should be significantly improved.

The second finding is that the cored hard phase obtained in the first finding has a grain growth suppressing effect, and the effect is equivalent to that of TiN when left alone in the sintered alloy.

The third finding is that the cored hard phase obtained in the first finding exists in the alloy in a metastable state during the disappearance due to the dissolution and the extrusion mechanism that occurs through the binder phase, and other hard phases and binders It functions as a source that supplies nitrogen to the phase. That is,
The chemistry of substitutional atoms (mainly Cr, Mo, w) and interstitial atoms (mainly nitrogen) contained in the binder phase in a large amount due to the presence of the hard phase, especially the cored hard phase obtained in the first finding. Interaction, so-called IS effect.

As described above, the present invention has been completed based on the first, second and third findings.

The high-strength sintered alloy of the present invention comprises titanium nitride, titanium carbide, a solid solution represented by (Ti, M) C, and a solid solution represented by (Ti, M) (C, N) (where M is Zr, Hf). , V, Nb, Ta, Cr, Mo, w represents one or more of the following) and a hard phase consisting of two or more of
In a sintered alloy consisting of 95 wt% and the remaining one or two binder phases of Co and Ni and inevitable impurities, the harmful hard phase is
0.5-5% by volume of the first cored hard phase formed by surrounding the core of titanium nitride with the outer periphery of (Ti, M) (C, N) solid solution, and the core of the remaining titanium carbide (Ti, M) The second cored hard phase surrounded by the outer periphery of the (C, N) solid solution and the core of the (Ti, M) C solid solution are (Ti, M) (C, N)
1 of other cored hard phases surrounded by the outer periphery of solid solution
It is characterized in that it is composed of two or more species.

Constituting the outer periphery of the hard phase in the high-strength sintered alloy of the present invention (Ti, M) (C, N) constituting a solid solution and the core of another cored hard phase (Ti, M) C solid solution, Remaining in a non-equilibrium state in the alloy structure, as the specific component structure of the (Ti, M) (C, N) solid solution constituting the outer peripheral part, for example, (Ti, M) (C, N), ( Ti, W, Ta) (C,
N), (Ti, W, Ta, Zr) (C, N), (Ti, w, Mo, Ta) (C, N), (Ti, W, Mo, T
a, Zr) C, N), (Ti, W, Mo, Ta, Nb, Zr) (C, N), and the like, which constitutes the core of another cored hard phase (Ti, M ) As a specific component structure of the C solid solution, for example, (Ti, W) C, (Ti,
W, Ta) C, (Ti, W, Mo, Ta) C, (Ti, W, Mo, Ta, Zr) C, (Ti, W, Mo, Ta,
Zr) C can be mentioned.

The hard phase in the high-strength sintered alloy of the present invention is a combination of the first cored hard phase and the second cored hard phase, a combination of the first cored hard phase and another cored hard phase, or A combination of the first cored hard phase, the second cored hard phase and another cored hard phase, especially in the case of a hard phase composed of the first cored hard phase and the second cored hard phase, It is preferable because it has excellent balance in both wear resistance and strength and has a stable life.

As for the hard phase in the high-strength sintered alloy of the present invention, when the first cored hard phase is less than 0.5% by volume, high performance based on the excellent properties of TiN including the grain growth suppressing effect is exhibited. Not done. On the contrary, when the first cored hard phase exceeds 5% by volume, the grain growth suppressing effect and the binder phase strengthening are saturated, and densification easily causes cavities, resulting in wear resistance of the sintered alloy and The strength is significantly reduced. Therefore, the first cored hard phase contained in the hard phase is defined as 0.5 to 5% by volume.

The binder phase in the high-strength sintered alloy of the present invention is Co and / or Ni, and Ti, Zr, Hf, V, Nb, which form other hard phases,
At least one of Ta, Cr, Mo and W metals, nitrogen and carbon is dissolved in Co and / or Ni to form a solid solution, and plays a role of strengthening the binder phase.

The method for producing a high-strength sintered alloy of the present invention includes titanium carbide powder, titanium nitride powder, and Zr, Hf, V, Nb, Ta, Cr, Mo, W carbide powder. Zr, Hf, V, Nb, Ta, Cr, Mo, W nitride powder or Ti, Z
Mixture powder consisting of Co powder and / or Ni powder and at least one kind of mutual solid solution powder in carbide, nitride of n, Hf, V, Nb, Ta, Cr, Mo, W and powder is used as a powder compact. After doing, for example 5x
It is characterized by firing and bonding at a temperature of 1500 ° C to 1550 ° C in a vacuum atmosphere of 10 ^-2 Torr.

Many of the high-strength sintered alloy production processes of the present invention are based on the ordinary powder metallurgy method, but special requirements are required for a part of the mixing / pulverizing process and a part of sintering conditions. First, in the powder that has been mixed and pulverized after being mixed in a prescribed amount, Ti
That is, the average particle size of N must be 1 to 2 μm. If the average particle size of TiN is less than 1 μm, in the present invention, since the sintering is performed at the high temperature as described above, the rate at which the TiN disappears due to Ostwald growth during the sintering becomes large and the TiN can be effectively left. Can not. On the other hand, if the average particle size of TiM exceeds 2 μm and becomes large, the grain growth of the first hard phase during sintering becomes remarkable, which is harmful to the toughness. For that purpose, when obtaining a mixed / pulverized powder by using an ordinary mixing / pulverizing machine, it is preferable to preliminarily pulverize the raw material powder excluding TiN as necessary and then add TiN to control the particle size.

Second, the sintering temperature must be 1500 ° C-1550 ° C. The TiN added to the TiC-based sintered alloy eventually disappears as a result of grain growth due to the melting / protruding mechanism in the sintering process when the sintering time is increased and / or the sintering temperature is increased. It forms a solid solution with other added carbides and nitrides. At that time, TiN, which is dissolving and disappearing in the liquid phase, simultaneously contains Zr, Hf, V, Nb, and
Although Ta, Cr, Mo, W elements and carbon diffuse and permeate, under normal sintering conditions, the rate of melting and reducing the diameter is significantly higher than the diffusion and permeation rate, In the process of disappearing
Even if TiN remains, the outer peripheral portion is not formed in the TiN. However, if the sintering temperature is set to a high temperature of 1550 ° C or higher (usually, TiN addition is mainly for suppressing grain growth, so the TiC-based sintered alloy containing TiN is not sintered at such a high temperature). It is considered that the diffusion / penetration rate is higher than the dissolution rate and the outer peripheral portion is formed. However, when high temperature sintering as described above is performed, the dissolution rate of TiN becomes higher than when performing low temperature sintering, so the sintering time in this case is longer than that when performing low temperature sintering. Needless to say, it has to be a short time. The sintering temperature is 15
If the temperature is higher than 50 ° C, the dissolution rate will be remarkably high.
It is difficult to leave TiN itself.

(Operation) In the high-strength sintered alloy of the present invention, the first cored hard phase in the hard phase functions to improve various characteristics of the sintered alloy,
In particular, the outer peripheral portion forming the first cored hard phase acts to improve the interfacial strength with the binder phase, and the TiN of the core portion forming the first cored hard phase has various characteristics of the sintered alloy. Has a strong effect on the improvement of. In the sintering process, the first
The cored hard phase acts as a grain growth inhibitor, and Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W dissolved in the binder phase and 6a of nitrogen and carbon, especially M, Mo, etc. It also has the function of promoting solid solution of the group metal into the binder phase.

(Example) TiC in Example 1 in an average particle size _{1~2μm, (Wo. 7, Tio} . 3) C, WC, TaC, Mo 2 C, Ni, Co and an average particle size of 2.
Using various raw material powders of TiN of 7 μm, first mix the raw material powders except TiN in a predetermined amount, mix them in a ball mill containing acetone and cemented carbide balls for 45 hours, and then add the TiN powder additionally, and further mix 3 Mixed for hours. The mixed powder thus obtained was pressed into a predetermined shape to obtain a powder-formed body. Then, sinter in a vacuum of 5 × 10 ^-2 Torr at 1520 ° C. for 30 minutes,
The sintered alloys 1, 2, 3 of the present invention were obtained.

Among the above manufacturing methods, in a vacuum of sintering conditions 5 × 10 ^-2 Torr,
Comparative Examples 1, 2 and 3 and sintering conditions of 5 × 10 ^-2 To were carried out in the same manner as above, except that sintering was carried out at 1450 ° C. for 60 minutes.
Comparative products 4, 5 and 6 were obtained in the same manner as above, except that sintering was carried out in a vacuum of rr at 1600 ° C. for 30 minutes. These invention products 1, 2, 3 and comparative products 1, 2, 3, 4, 5, 6,
Table 1 shows the composition of each of the above.

The hard phases of the invention product and the comparative product thus obtained were investigated by a metallographic microscope, a scanning electron microscope and an X-ray microlyzer, and the results are shown in Table 2. Further, the hardness and resistance strength of each sintered alloy were measured, and the results are also shown in Table 2.

Example 2 The various raw material powders used in Example 1 were blended in the compositions of 4,5,6,7,8 of the present invention and comparative products 7,8,9,10 shown in Table 3, and the present invention 5 × 10 ^-2 for both product and comparative product
A sintered alloy was obtained under the same manufacturing conditions as in Example 1 except that sintering was performed at 1520 ° C. for 30 minutes in a Torr vacuum. The hard phase, the hardness and the bending strength of the thus obtained invention product and comparative product were examined in the same manner as in Example 1, and the results are shown in Table 4.

Example 3 Inventive products 1 to 8 and comparative products 1 to 10 obtained in Example 1 and Example 2 were subjected to a cutting test under the following conditions (A) and (B) to show fracture resistance and wear resistance. And the thermal plastic deformation were investigated, and the results are shown in Table 5.

(A) Cutting test conditions (fracture resistance test) Cutting test by milling Work material S45C (H _B 180) 50mm × 150mm square material Chip shape SPGN422 (0.1 × -30 ° straight line honing) Cutting speed 108m / min Depth of cut 1.5 mm Life judgment First, starting from feed of 0.15 mm / blade, cutting 150 mm, and if there is no loss, sequentially 0.21 mm / blade, 0.25 mm / blade, 0.30 mm / blade, 0.37 mm / blade, 0.343 mm / blade, 0.50 mm / blade and feed amount were increased, and the limit feed amount to withstand chipping or chipping was determined.

(B) Cutting test conditions (wear resistance and heat plastic deformation) Work material SNCM439 (H _B 245) 250 φmm Chip shape SPGN422 (0.1 × -30 ° straight line honing) Cutting speed 180m / min Depth of cut 1.5mm Feed Speed 0.39mm / rev Cutting time 3min (Effects of the Invention) As a result, the high-strength sintered alloys of the present invention have almost the same composition as the conventional products when compared with ones having the same composition, but judged by the flank wear amount in the cutting test. Then, there is an effect that the wear resistance is improved by about 50%. Further, the high-strength sintered alloy of the present invention has a bending strength of about 10% to 50%.
%, And the fracture resistance strength in the cutting test is improved 2-3 times. Furthermore, the high-strength sintered alloy of the present invention is significantly superior in wear resistance, fracture resistance and heat plastic deformation compared to the sintered alloys deviated from the present invention.

From these, the high-strength sintered alloy of the present invention has a significantly improved service life when a sintered alloy such as a conventional cemented carbide or cermet is used as a wear-resistant tool component or a cutting tool component, which is a usage region. , An industrially useful alloy.

 ─────────────────────────────────────────────────── ─── Continuation of the front page Judge Chief Makoto Nagase Judge Judge Nakajima Kiyoshi Judge Asahi Aizawa (56) Reference JP 61-73857 (JP, A) JP 60-106941 (JP, A) JP 60 -2647 (JP, A) JP-A-57-126945 (JP, A) JP-A-57-57866 (JP, A) JP-A-56-156738 (JP, A)

Claims (1)

[Claims] 1. Titanium nitride, titanium carbide, a solid solution represented by (Ti, M) C, and a solid solution represented by (Ti, M) (C, N) (however,
M represents one or more of Zr, Hf, V, Nb, Ta, Cr and Mo.W)
In a sintered alloy consisting of 75 to 95% by weight of a hard phase consisting of two or more members in the group, and the remaining one or two binder phases of Co and Ni and inevitable impurities, the hard phase is a nitriding layer. 0.5 to 5% by volume of the first cored hard phase in which the titanium core is surrounded by the outer periphery of the (Ti, M) (C, N) solid solution
The core of the remaining titanium carbide is surrounded by the outer periphery of the (Ti, M) (C, N) solid solution and the core of the (Ti, M) C solid solution is (Ti, M). ) A high-strength sintered alloy characterized by comprising one or two of other cored hard phases surrounded by the outer periphery of a (C, N) solid solution.