JPH04231467A - Coated tic-base cermet - Google Patents

Abstract

PURPOSE:To obtain a TiCN-base cermet material excellent in wear resistance and toughness by coating the surface of a cermet cutting material essentially consisting of Ti and W and having a metallic carbon nitride hard phase blended with Nb with a Ti-contg. hard film. CONSTITUTION:The surface of a TiCN-base cermet material constituted of a hard phase consisting of the carbon nitride of Ti, W and Nb as a base metal and a bonding phase of iron group metals, having a compsn. expressed by a formula 1, in which a hard phase has a structure with a core and having a structure in which the content of Ti and N is higher in a core part and the content of W, Nb and C is higher in a peripheral part is coated with a Ti-base hard film having Ti content higher that of the cermet, in which the content of iron group metals as the bonding phase is regulated to <=100ppm and is not substantially contained and having <=0.4mum average grain size. A TiCN-base cermet material in which the quality of the upper face to be cut by the above cermet is good and small in the consumption of the cermet as a cutting material can be obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated TiCN-based cermet with excellent wear resistance and toughness, and more particularly to a coated TiCN-based cermet that can be used as a cutting tool and has a good finished surface of a workpiece.

0002

[Prior Art] In recent years, cermets composed of a hard phase consisting of double carbonitrides of elements of groups 4a, 5a, and 6a of the periodic table and a binder phase consisting of iron group metals have been used as sintered bodies for cutting. Now you can.

[0003] Such cermets have so far been made of Ti.
TiC-based cermets, whose main component is C, have been the mainstream, but since they have inferior fracture resistance compared to cemented carbide, which has long been used as tool materials, by adding nitrides to this system, So-called TiCN-based cermets with improved toughness have been proposed.

[0004] A typical example of this TiCN-based cermet is Japanese Patent Publication No. 51201/1983, in which (T
i, W, Ta, Mo) A hard phase consisting of CN and Ni, C
A cermet is disclosed in which the hard phase is composed of a core rich in Ti and nitrogen, and a binder phase consisting of W, Ta, Mo.
It is said that it exhibits a cored structure composed of a carbon-rich periphery and a carbon-rich peripheral region.

Furthermore, according to this prior art, Mo and Mo2C as hard phase forming components exist in the periphery of the cored structure and improve the wettability of the hard phase with the binder phase. It is considered an essential ingredient. 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.

[0006] Carbon (C) and nitrogen (N), which form the hard phase, are major factors that determine the toughness and hardness of cermets.Recently, efforts have been made to increase the toughness of cermets by incorporating a large amount of nitrogen. Attempts are being made to do so.

Recently, however, various improvements have been made to the TiCN-based cermets, including improvements in the hard phase component and in the core or peripheral portion of the cored structure. For example, in Japanese Patent Publication No. 63-3017, Mo and Mo2C are not effective in improving wettability with the binder phase in systems containing a large amount of nitrogen, and inhibit sinterability. It has been proposed to form a TiN phase systematically without adding
No. 39342 proposes adding NbC in addition to Ti, Ta, and W as a hard component to improve the thermal shock resistance and oxidation resistance of cermet.

[0008]

[Problems to be Solved by the Invention] However, according to these prior art techniques, cermets have not been fundamentally improved, and the cutting characteristics of cemented carbide, which has been the mainstream tool material, still deteriorate. Remaining. Moreover, as cutting conditions become more severe, tool materials are required to have even higher properties.

Therefore, the present inventor conducted various studies on the composition of conventional cermets, and found that M as a hard phase component
Although the addition of O or Mo2C is effective in improving wettability with the binder phase, Mo2C itself is significantly inferior to TiC in properties such as hardness, thermal conductivity, Young's modulus, and oxidation resistance. In a cored structure, the presence of a peripheral portion containing Mo tends to cause a decrease in wear resistance particularly as a tool material.

Therefore, it is considered better to not add Mo as a hard phase forming component as in Japanese Patent Publication No. 63-3017, but according to the structure of Japanese Patent Publication No. 63-3017, T
It has been found that the precipitation of the iN phase causes the interface between the TiN phase and the binder phase to become a breaking point within the sintered body because TiN itself has very poor wettability with the binder phase, resulting in a decrease in strength.

On the other hand, according to JP-A No. 64-39342, although the oxidation-resistant effect of Nb is recognized, the oxidation-resistant effect due to the addition of Ta as a hard phase forming component is not as strong in cermets containing a large amount of nitrogen. It is not effective, and on the contrary, it impedes sinterability, and since it is necessary to set the sintering temperature high to obtain a dense body, it causes grain growth of the sintered body particles, which reduces the wear resistance of the cermet. It has been found that there is a problem of lowering the

[0012] Furthermore, regarding the finished surface of the workpiece as an item other than wear resistance and chipping resistance, in conventional cermets, the workpiece material reacts with iron group metals, which are binder phase components, and W, which is a hard phase forming component. However, there was a problem in that the cut surface became rough.

[0013]

[Means for Solving the Problems] Based on the above findings, the present inventors have studied a cermet that has excellent wear resistance, chipping resistance, oxidation resistance, and quality of the finished surface of the workpiece. As a result, Ti is the metal component forming the hard phase.
, W is an essential component, and instead of conventionally adding Mo and Ta, Nb is selected and these are blended in a specific range,
The presence of Nb as well as W in the periphery of a cored structure can effectively modify the periphery, thereby improving wear resistance, chipping resistance, and oxidation resistance. It was discovered that by coating the surface of the material with a hard film containing titanium-rich Ti with a small particle size, reactivity with the work material can be suppressed and a tool with an excellent finished surface can be obtained, and the present invention reached.

That is, the present invention provides a TiCN-based cermet consisting of a hard phase containing at least Ti, W and Nb as essential components and a binder phase consisting of an iron group metal, which The composition of other components excluding the iron group metal is as follows: (Ti a Nb b W c) (C
u Nv )z where 0.50≦a≦0.95,
0.05≦b+c≦0.5, 0.04
≦b/b+c≦0.95, a+b+c=1
0.40≦v≦0.60, u+v=1
T that satisfies 0.80≦z≦1.0 and has a structure in which the hard phase exhibits a cored structure, Ti and nitrogen are rich in the core, and W, Nb and carbon are rich in the periphery.
The iCN-based cermet is used as a base material, and its surface is coated with a film that is richer in Ti than the cermet, contains substantially no iron group metals at 100 ppm or less, and has an average particle size of 0.4 μm or less. That is.

The coated TiCN-based cermet of the present invention basically consists of a base material consisting of a hard phase and a binder phase, and a hard coating layer formed on the surface of the base material.

In the cermet base material, Ti, which is the main component forming the hard phase, exists in the sintered body as approximately TiCN, and its amount is a major factor determining the strength and hardness of the cermet. If a) in Equation 1 is less than 0.5, the wear resistance and affinity for metals, which are characteristics of cermet tools, will be insufficient, and if it exceeds 0.95, the fracture resistance will decrease. Note that the Ti amount (a) is 0
．． It is particularly desirable that 70≦a≦0.9.

[0017] Nb and W are auxiliary components that form a hard phase, and both 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, if the ratio (b+c) of the total amount of Nb and W in Equation 1 is less than 0.05, the fracture resistance will be insufficient, and if it is larger than 0.5, the wear resistance will be poor and the reactivity with the work material will decrease. tends to be higher. Note that it is particularly desirable that the (b+c) value is 0.10≦b+c≦0.30.

Among these, W is an essential component for improving the wettability of the hard phase with the binder phase and increasing toughness as WC, but when the hard phase is (Ti, W)
When made of CN, 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 various properties, but as mentioned above, Mo2C itself is a main component of the hard phase, such as TiC and TiCN. Since its properties are inferior to that of cermet, it actually deteriorates the properties of the cermet. In addition, sinterability is greatly influenced by the amount of binder phase in the system, but when the binder phase is the same amount, the addition of TaC reduces sinterability, requiring high temperature firing, which causes crystallization. The wear resistance of the cermet deteriorates as the particle size of the cermet increases.

On the other hand, Nb is Mo2 as a carbide.
Since it has superior properties in itself compared to C, it greatly contributes to improving the properties of cermet, and it does not affect sinterability, so it has excellent wear resistance, oxidation resistance,
It was found that fracture resistance can be improved.

From this relationship, the total amount of W and Nb (b
If the ratio (b/b+c) of the amount of Nb (b) to +c) is smaller than 0.4 in Equation 1, the wear resistance and oxidation resistance will be poor, and if it is larger than 0.8, the fracture resistance will be reduced.

According to the cermet of the present invention, the addition of Mo and Mo compounds to the cermet base material should be avoided for the reasons mentioned above, and the amount should be controlled to 0.5% by weight or less in the cermet base material. is desirable.

[0022] Similarly to Mo, Ta is said to have the effect of improving the oxidation resistance of the system and suppressing crater wear.
Although it has traditionally been considered an essential component, it has almost no effect in the system of the present invention, and rather tends to impede sinterability. Therefore, it is desirable that the amount of Ta in the TiCN-based cermet of the present invention is also 0.5% by weight or less.

On the other hand, the amount of nitrogen and carbon is a very important factor in determining the hardness and toughness of cermet, and especially as the amount of nitrogen increases, the toughness tends to improve. When this happens, a problem arises in that gas from decomposition of nitrides during firing remains in the voids of the sintered body. Therefore, in the above formula, the amount of nitrogen (v) is 0.4
If it is smaller, the toughness will decrease and fracture resistance will be insufficient,
If it exceeds 0.6, voids will occur within the sintered body, resulting in a lack of reliability.

Furthermore, if the ratio (z) of the amount of nitrogen and carbon to the total amount of Ti, W, and Nb is smaller than 0.8, the sinterability will deteriorate and voids will remain, and if it is larger than 1.0, free carbon will be This results in a decrease in strength. Desirably, 0.85≦z≦1.0.

[0025] The iron group metal forming the binder phase in the present invention includes Ni and/or Co, preferably composed of Ni and Co, particularly when the molar ratio of Co/Ni+Co is 0.5 to 0.9. It is preferable from the viewpoint of improving wear resistance.

[0026] Moreover, this iron group metal has a concentration of 3 to 4 in the system.
Preferably it is present in a proportion of 0% by weight, especially 5-30% by weight.

According to the above-mentioned cermet, due to the low Ti content in the surface layer, when cutting is performed using structural alloy steel SCM435 as a work material, for example, W etc. in the cermet react with the work material. However, the finished surface may become rough. Therefore, according to the present invention, the surface of such a TiCN-based cermet is coated with a hard film containing Ti.

In order to suppress the reactivity between the cermet base material and the workpiece material, this hard film has a Ti content richer than that of the base material, especially the Ti content in the surface layer. This makes it possible to suppress the reactivity of the cermet with the work material described above. In addition, when forming a hard film on the cermet surface, iron group metals that are abundant on the cermet surface diffuse into the hard film, which deteriorates the original properties of the hard film, such as its hardness and reactivity with the workpiece material. I'll let you. Therefore, this hard film has an iron group metal content of 100%.
It is necessary to control it to below ppm, especially below 70 ppm.

Furthermore, the grain size of the crystals constituting the hard film is
It is a factor that influences the hardness and strength of the film, and the smaller the crystal grain size, the harder, higher strength, and higher toughness the film becomes. Therefore, according to the present invention, the crystal grain size of this hard film is set to 0.4 μm.
In particular, by controlling the thickness to 0.3 μm or less, it is possible to exhibit its original function as a hard film, and to prevent particle drop-off due to breakage in the film, and thus film peeling.

[0030] The Ti-containing hard film in which the Ti content is higher than that in the cermet includes TiC, TiN, Ti
CN or the like is suitable, and these films may contain oxygen depending on the case.

[0031] This hard film has a thickness of 1 to 10 on the cermet surface.
It is desirable to coat with a thickness of 1 μm.
If the thickness is smaller than 10 μm, the effect of suppressing the reactivity with the work material will be small, and the surface of the work material will become rough. If it is thicker than 10 μm, the film will easily peel off during use due to the difference in thermal expansion between the hard film and the base material.

Next, the method for producing the above-mentioned coated TiCN-based cermet will be explained. First, powders of carbides, nitrides, and carbonitrides of Ti, W, and Nb and powders of iron group metals are used as raw material powders to form a final sintered body. Weigh and mix so that they are in the proportions mentioned above.

Next, the above-mentioned mixed powder is molded by a known molding means such as press molding, extrusion molding, injection molding, etc., and then fired.

[0034] In the firing, it is necessary to adjust the firing conditions so that a cored structure is formed.
It is obtained by firing at a temperature of 0 to 1600°C. Note that the sinterability may be slightly reduced by suppressing the amount of Mo, which has excellent wettability with iron group metals, but in this case, the amount of iron group metals should be increased or the amount of carbon powder should be increased from 0.05 to
Sinterability is improved by adding 3% by weight.

[0035] The Ti compound-based raw material powder to be used includes TiC, TiCN, TiN, etc.
If a large amount of N powder is used, it may remain as a TiN phase in the final sintered body as disclosed in JP-A-64-39342, but as mentioned above, this TiN phase deteriorates the mechanical properties of the cermet. Therefore, TiC is used as a raw material.
or TiCN, and consideration should be given to avoid formation of a TiN phase.

According to the present invention, carbides, nitrides, carbonitrides, etc. such as Zr, Hf, Cr, and V are further added to the above-mentioned system for the purpose of improving the characteristics, and in the above-mentioned equation 1, By substituting a part of Ti or Nb, properties can be improved. In particular, by substituting a part of Nb with V, the effects of Nb are further promoted, and the wear resistance is improved especially during high-speed cutting of cermet. can greatly improve performance. The Nb/V atomic ratio at this time is preferably 1 to 10, particularly 2 to 6.

Next, a hard film containing Ti is formed on the surface of the cermet obtained as described above. Specifically, chemical vapor deposition methods (CVD methods) such as thermal CVD, plasma CVD, and laser CVD, physical vapor deposition methods (PVD methods) such as sputtering and ion plating, or vapor phase impregnation methods are employed. However, in order to control the particle size of the hard film to 0.4 μm or less based on the present invention, ion plating, plasma CVD, and sputtering are preferable.

[0038] Also, the amount of iron group metal mixed into the hard film was reduced to 1
When limiting the amount to 00 ppm or less and considering the film adhesion strength, ion plating, plasma CVD, etc. are preferable.In particular, the ion plating method reduces the formation of crystal grains in the film due to the low film forming temperature. Atomization control is easy, and since diffusion of iron group metals from the base material is suppressed, mixing into the film can be prevented. Furthermore, during film formation, it is also necessary to consider eliminating parts made of iron group metals as much as possible in the equipment in the reactor.

[0039]

[Function] Nb, which is one of the hard phase forming components in the TiCN-based cermet used in the present invention, has superior properties as a carbide compared to Mo2C, so it is present in the peripheral part of the cored structure. By existing together with W, the wear resistance, oxidation resistance, and chipping resistance of the cermet can be improved.

Furthermore, as hard phase forming components, Mo, Ta, etc. are inferior to those of the present invention in terms of wear resistance, chipping resistance, and finished surface, as is clear from the examples described later. As the number increases, the characteristics deteriorate.

Furthermore, in such a base material, the amount of Ti on the surface portion is relatively smaller than that inside, so the reactivity with the work material tends to be high. By forming the film, the ratio of Ti in the surface portion can be increased, so that the reactivity with the work material can be suppressed, and the surface condition of the work material after processing can be improved.

[0042]

[Example] Average particle size as raw material powder is 1 to 1.5 μm
TiC, TiCN, WC, NbC, Mo2C, Ta
After weighing and mixing C, Ni, and Co powders so that the composition of the final sintered body would be in the proportions shown in Table 1, 1.5 tons
It was press-molded into a chip shape for TNGA160408 at a pressure of /cm2. Next, these molded bodies were heated to 1400 ~
It was fired for 1 hour in a vacuum atmosphere at a firing temperature of 1600°C.

As a result, when the structures of the obtained sintered bodies were confirmed using an electron microscope, the hard phases in all cases had a cored structure, and no precipitation of TiN phase was observed. In addition, regarding sample number 1, the amount of elements in the core part and peripheral part of the cored structure was investigated using TEM. The results are shown in FIGS. 1 and 2. According to these figures, a large amount of Ti exists in the core,
It can be seen that W and Nb are present in large quantities in the peripheral area.

[0044] For the hard film, TiN, TiCN, and TiCNO films were formed to a film thickness of 3 μm using an ion plating method with the base material temperature set at 300 to 700°C. Further, the average grain size of crystals in the film was measured by SEM, and the content of iron group metals in the film was measured by ICP analysis.

Next, each sample was subjected to a wear test and a chipping test under the cutting conditions shown below, and the amount of flank wear and the number of non- chipping corners after cutting were investigated. The results are shown in Table 1.

(Abrasion test) Work material: SCM435 Cutting speed: 250 m/min, depth of cut
2mm Feed 0.3mm/rev Cutting time 10min

(Defect test) Work material SCM435 (4 grooves) Cutting speed 100 m/min depth of cut
2mm Feed 0.3mm/rev Cutting time 1min

[0048] In addition, for evaluation of the finished surface, a surface roughness meter is used to express the condition of the finished surface of the workpiece material as Rmax. It was evaluated as ○.

[0049]

[Table 1]

[0050]

[Table 2]

According to Tables 1 and 2, the samples of the present invention all show excellent cutting performance, but the base material contains Ti and W.
, Nb, C, and N compositions and film properties outside the scope of the present invention, no satisfactory results were obtained.

Further, even if the base material had a composition within the range of the present invention, favorable characteristics could not be obtained with samples in which the average particle size and iron group metal content of the coating layer on the surface were large.

[0053]

[Effects of the Invention] As detailed above, the TiCN of the present invention
In addition to Ti and W as hard phase components, Nb is selected as an essential component of the base cermet, and N is added to the periphery of the cored structure.
By the presence of b and the formation of a predetermined film on the surface, it has excellent wear resistance and chipping resistance, and can improve the quality of the finished surface after cutting the work material, making it suitable as a material for tools. Longer life can be achieved.

[Brief explanation of the drawing]

FIG. 1 shows the results of TEM analysis of the core of the cored structure in the base material of the coated TiCN-based cermet of the present invention.

FIG. 2 shows the results of TEM analysis of the periphery of the cored structure in the base material of the coated TiCN-based cermet of the present invention.

Claims (2)

[Claims] Claim 1: Consisting of a hard phase containing at least Ti, W and Nb and exhibiting a cored structure, and a binder phase consisting of an iron group metal, the iron group metal and inevitable impurities being excluded from the overall composition. Other component compositions [(Ti)a
When expressed as (Nb)b (W)c][(C)u (N)v]z, a+b+c=1, 0.50≦a≦0.95,
0.05≦b+c≦0.5, 0.40≦b/b+c≦0
．． 95, 0.40≦v≦0.60, 0.80≦z≦1.
0, u+v=1, and in the cored structure,
Ti and nitrogen are rich in the core, W, Nb and carbon are rich in the periphery on the surface of the TiCN-based cermet, which is richer than the amount of Ti in the cermet and has an average particle size of 0.4 μm or less,
A coated TiCN-based cermet characterized by being coated with a hard film containing Ti with an iron group metal content of 100 ppm or less. 2. The coated Ti according to claim 1, wherein the Mo content in the TiCN-based cermet is 0.5% by weight or less.
CN-based cermet.