JPH03240929A - High toughness cermet alloy - Google Patents

Abstract

PURPOSE:To manufacture a new high toughness cermet alloy having high chipping resistance by constituting the compsn. of the core part of a cermet alloy composed of a B1 type hard phase having a dual core structure and a bonding metallic phase of a low N hard phase and a high N hard phase in a specified ratio. CONSTITUTION:A cermet alloy is prepd. from a B1 type hard phase having a dual core structure and a bonding metallic phase. The bonding metallic phase is composed of one or more kinds among iron-group metals and its weight is regulated to 5 to 30%. The hard phase is composed of a mixture or mutual solid soln. of carbides, nitrides, carbon nitrides or carbon nitrogen oxides obtd. by incorporating Ti and W with one or more kinds among the groups 4a, 5a and 6a in a periodic table and its weight is regulated to 70 to 95%. At this time, as for the hard phase, the compsn. of the core part having a dual core structure is constituted of a primary hard phase of Ti(CxNy)eta (y<=0.3, x+y=1 and 0.5<=eta<=1) with <=30mol% nitrogen content and a secondary hard phase of Ti(CxNyOz)eta (y<=0.7, x+y+z=1, 0.01<=z<=0.2 and 0.5<=eta<=1) with >=70mol% nitrogen content, and the secondary hard phase occupies 5 to 20% to the hard phase.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a novel chip that has excellent thermal shock resistance and high temperature chemical stability, and has extremely high chipping resistance as a cutting chip for cutting tools such as milling cutters that perform interrupted cutting. This article relates to a high-toughness cermet alloy and its manufacturing method.

(Prior Art) Cermet alloys for tools initially started from Tic-based alloys containing TiC as a hard phase forming component. TiC-based cermets have lower reactivity with iron than cemented carbide, and although they have excellent wear resistance, surface roughness, and high-speed machinability, they have poor thermal shock resistance, edge strength, and plastic deformation resistance. There are many problems with this. Therefore, it has poor fracture resistance and is limited to light cutting finishing.

It was discovered that the lack of fracture resistance, which is a drawback, could be improved by adding TiN, and since then various companies have produced TiN-added surfactants.
If it is increased by more than 0%, denitrification occurs during sintering, creating bores and becoming brittle, so a solid phase has been used. Therefore, ratios that can be applied to rough machining and milling with improved fracture resistance have appeared (for example, Japanese Patent Application Laid-Open No. 49-7
8609).

(Problems to be Solved by the Invention) However, the above-mentioned cermet is still susceptible to thermal cranking (thermal cracking) due to thermal shock as well as mechanical shock during heavy cutting or severe interrupted cutting. Especially high efficiency (
In high-feed milling, there are still shortcomings such as short service life and lack of reliability in cutting edge strength, and expectations are growing in the machine tool industry for the emergence of high-toughness cermet alloys that solve these problems. There is.

In order to improve this drawback, a manufacturing technology for a cermet alloy having a hard phase with an N content of 0.3 has been developed by increasing the amount of nitrides such as TiN added, and has achieved a certain degree of fracture resistance. Improved. This makes it possible to perform interrupted cutting and wet cutting, resulting in improved finishing.In this case, increasing the N content improves thermal shock resistance, but reduces wear resistance. Therefore, in the region of ≧C+N 0.5, the wear resistance and plastic deformation resistance decrease significantly due to a decrease in Young's modulus, cutting resistance increases, and the temperature at the cutting edge increases significantly, making it difficult to improve thermal shock resistance. Since it acts as an erasing effect, the fracture resistance actually worsens. Therefore, there is a limit to the conventional improvement in fracture resistance simply by adding and increasing the amount of nitride or carbonitride, and this is a problem in making cermet alloys even tougher, and new measures are required. was.

(Means for Solving the Problems) The present invention was developed as a result of intensive research to overcome the limits of fracture resistance of conventional products.
As shown in the figure, we found a solution by obtaining an alloy constituent phase that is completely different from the conventional one.

That is, a first hard phase consisting of a low-N carbonitride and a second hard phase consisting of a high-N carbonitride are mixed in a certain quantitative ratio, or AjF or Si is mixed in the binding metal phase. They found that fracture resistance can be significantly improved by uniformly dispersing heat-resistant compounds.

First, regarding the hard phase, as shown in Figure 2, as the hardness increases, thermal shock resistance uniformly improves, but flank wear resistance and Young's modulus gradually decrease until the N content reaches 50%. Above that, it drops rapidly.

For this reason, the fracture resistance, which appears as the overall performance of these properties, gradually improves up to 50% N content, but at 50%
If it exceeds this, there will be a downward trend. As a means to prevent this decrease and further improve it, we have attempted to suppress the rapid decrease in flank wear resistance while maintaining thermal shock resistance. For this reason, two types of hard phases with different N contents were used.

That is, in the core composition of the B type hard phase, which has a double cored structure, the N content is 30-01% or less.
By using the first hard phase consisting of CN), flank wear resistance and Young's modulus are improved. However, due to the presence of a low-N hard phase, the thermal shock resistance will be lower than that of an alloy with a 50% N content.
Compensation was made by establishing a second hard phase in the system.

That is, in the core composition, a certain amount of a phase having an N content of 70mo5% or more is contained as the second hard phase. In this case, by containing a small amount, the N content can be increased to 50 mo.
It is necessary to have heat resistance properties equal to or higher than that of an alloy made of 1% of one type of hard phase. For this reason, Ti
Instead of using Ti (CN) as a core composition, Ti (CNO) in which 1 to 20% of TiO, which has mutual solid solubility in Tic and TiN and has high temperature chemical stability comparable to Al tax, was dissolved in solid solution was used. As a result, thermal shock resistance maintained the peak value of conventional alloys, and chemical stability was improved.

As described above, the first film made of low N-based Ti (CN)
By containing a hard phase consisting of a hard phase and a second hard phase consisting of high N-based Ti (CNO) in a fixed ratio, an alloy with significantly higher fracture resistance than conventional alloys can be obtained, as shown in Figure 2. A surprising fact has been revealed.

Further, as shown in FIG. 3, it was found that there is an appropriate value for the content of the second hard phase, and that it is effective when the content of the second hard phase is 5 to 20% by weight in the total hard phase.

Furthermore, in order to further improve fracture resistance, we attempted to strengthen the binder phase. Conventionally, Al or Si compounds have been considered to act as defects and cause embrittlement in cermet alloys, and have been excluded as additive elements. However, it has been found that when a certain amount of Ti is dispersed in the bonded metal phase as an intermediate compound with Ti by reactive sintering, it significantly contributes to improving the heat cracking resistance at high temperatures. That is, by adding 0.5 to 20% by weight of Al or Si to the bonded metal phase, these Al or Si can be added to the ri(cxN
y) A heat-resistant intermediate compound produced by reaction with an excess of Ti corresponding to the non-stoichiometric atomic fraction (1-η) of y or Ti (C, N, 0□), e.g. TiA l :ll TiA
l, Ti3A l + TiSi3°TiSi,
It can be inferred that TizSi and the like are uniformly dispersed and present in the bonded metal phase, thereby inhibiting the development of thermal crank and thus improving fracture resistance.

Next, the reason for limiting the range of ingredients in the cermet alloy of the present invention as described above will be described.

Regarding the binder metal phase, the binder metal phase becomes a liquid phase during sintering and acts to retain the hard phase particles and imparts toughness to the alloy. If the content of this phase component is less than 50%, sintering will be insufficient and at the same time the alloy will lack toughness. On the other hand, if it exceeds 30%, the hardness decreases significantly and wear resistance deteriorates, so it is limited to 5 to 30%.

Regarding the first hard phase -ri (cxNy), this hard phase is a phase set to impart wear resistance and plastic deformation resistance to the alloy and further improve sinterability. Therefore, the N content is set at 3011O as the limit at which these properties do not deteriorate rapidly.
It was defined as 1% or less.

In addition, if the non-stoichiometric molar fraction η is too small, excessive Ti atoms will be generated and cause embrittlement of the alloy, so 0.5≦η≦
It was set to 1.

Regarding the second hard phase - Ti (C, N, 0-) y, this hard phase is a phase designed to impart thermal shock resistance, therefore thermal cracking resistance and high temperature chemical stability to the alloy. If the main hard phase accounts for less than 5% by weight of the total hard phase,
It has no effect on these properties, and if it exceeds 20%, wear resistance and sinterability deteriorate, so its content was set at 5 to 20% by weight in the total hard phase.

Next, TiN has an effect on thermal shock resistance, but the desired effect cannot be obtained unless its content reaches 701Io1%, so the N content should be 70 mol! % or more.

Furthermore, TiO is effective for chemical stability at high temperatures, but it has no effect if its content is less than 1%, and if it exceeds 20% it causes embrittlement, so the content should be adjusted to 0.01≦z≦0. It was set as 2.

For Al or Si, these components are the Ti(CxNy)v- or Ti(
CxNyOg) reacts with relatively excess Ti in y to form a heat-resistant intermediate compound, which has the effect of inhibiting the propagation of thermal cracks by uniformly dispersing it in the bonded metal phase, and is Effective in strengthening the bonded phase. If the content of these components is less than 0.5% by weight in the binder metal phase, there is no effect, and if it exceeds 20%, the alloy deteriorates, so the content was set to 0.5 to 20% by weight. .

(Example) ■ Using various commercially available raw materials with an average particle size of 1 to 3 μm, the first
The invention alloy a % i shown in the table and comparative alloys 1 to 5 were mixed wet in a ball mill using acetone as an organic solvent, and then 2% paraffin was added to form a dry powder, which was then pressed in a press. Molded. These molded bodies were heated to 1450°C in a vacuum sintering furnace.

Sintering was carried out under conditions of 1 torr and 1 h to produce various alloys shown in Table 1.

These sintered bodies are ground with a diamond grindstone to form 5PGN.
Finished in a 120308 TN chip shape. A milling test was conducted on these chips under the following conditions, and the defect rates were compared. As a result, the alloy of the present invention had more than twice the fracture resistance as compared to the comparative alloy.

Cutting conditions v: 150 m/5inf: 0.4
w/rev, blade d: 2 days Cutter diameter = 150m Chip shape: 5PGN120308 TN cutting material:
SNCM439 (100xllOx200)■ Lifespan judgment: at 10 baths/corner■ The present invention alloy j- shown in Table 2 was prepared in the same manner as in Example 1.
Chips of i and comparative alloys 6 to 8 were prepared.

Intermittent turning tests were conducted on these chips under the following conditions, and the chipping life was compared, and the results shown in Figure 4 were obtained.0 The alloy of the present invention has more than twice the cutting life in the low feed range compared to the comparative alloy. In the high feed range, the chipping life was more than 1.2 times longer.

Cutting conditions Cutting material: 545C (HB 188-195) Chip shape: SNMG433 Cutting speed: 300g+/Pengin.

Delivery: 0.315 Tsuru/rev.

Depth of cut: 4.0 Tsuru Holder: PSDNN2525

[Brief explanation of drawings]

Figure 1 is a structural phase diagram of a cermet alloy, in which (a) shows a conventional alloy, ([+) shows an embodiment of the present invention, (c) shows another embodiment, and Fig. 2 shows a product of the present invention. Figure 3 is a diagram showing the relationship between N content and properties of conventional products, Figure 3 is a diagram showing the relationship between Ti (CNO) content and fracture resistance, and Figure 4 is a comparison diagram of interrupted turning tests.

Claims (3)

[Claims] (1) Consisting of a B_1 type hard phase having a double cored structure and a binding metal phase, the binding metal phase contains 5 to 30% by weight of one or more iron group metals, and the hard phase contains Ti
and W, and a mixture or mutual solid solution compound of carbides, nitrides, carbonitrides, or carbonitrides containing one or more transition metals of groups 4a, 5a, and 6a of the periodic table. In the cermet alloy containing 95% by weight, the hard phase is Ti(C_xN_y)_η with a nitrogen content of 30 mol% or less in the core composition of the double cored structure.
(However, y≦0.3, x+y=1, 0.5≦η≦1) and Ti with a nitrogen content of 70 mol% or more.
(C_xN_yO_z)_η (y≧0.7, x+y
+z=1, 0.01≦z≦0.2, 0.5≦η≦1), and the weight ratio of the second hard phase in the hard phase is A high toughness cermet alloy characterized in that the toughness is 5 to 20%. (2) The binding metal phase contains Al or Si in a weight ratio of 0.5% or more and 20% or less in the binding metal phase, and furthermore, these Al or Si contains the Ti(C_xN_y).
The high-toughness cermet alloy according to claim 1, wherein the cermet alloy is dispersed as an intermediate compound produced by reacting with excess Ti corresponding to the non-stoichiometric atomic fraction (1-η) of Ti(C_xN_yO_z)_η or Ti(C_xN_yO_z)_η. (3) The first and second hard layers further include one or more of WC, TaC, HfC, and NbC as a third hard phase in the alloy. High toughness cermet alloy.