JP5381616B2 - Cermet and coated cermet - Google Patents

Description

The present invention relates to a cermet and a coated cermet used for a cutting tool or the like.

Cermet has excellent wear resistance, and when it is cut with cermet, a smooth and beautiful finished surface can be obtained. Therefore, cermet is widely used for finish cutting. As a conventional technique related to cermet, there is a cermet in which the toughness is improved by controlling the distribution of the carbonitride phase of cermet (see, for example, Patent Document 1). Further, there is a cermet whose performance is improved by controlling the structure of carbonitride (see, for example, Patent Document 2).

Japanese Patent No. 3359481 Japanese Patent No. 2697553

In recent years, further high-efficiency machining has been demanded in cutting. For example, since highly efficient machining is possible by reducing the number of times of exchanging the cutting tool, a cutting tool having a longer life than before has been demanded. Conventional cermets and coated cermets are excellent in wear resistance, but have a problem that they are easily broken and have a short life. The present invention has been made to solve such problems, and an object thereof is to provide a cermet and a coated cermet having excellent wear resistance and fracture resistance.

The present inventors have studied a method for improving fracture resistance without reducing the wear resistance of the cermet. As a result, it was found that the loss of cermet is mainly caused by thermal shock, and that it is very effective to improve the thermal conductivity of cermet in order to reduce the loss of cermet due to thermal shock. In order to improve the thermal conductivity of the cermet, it is preferable to contain a WC phase having a high thermal conductivity. However, if there are many WC phases, the wear resistance is lowered, so that it cannot be increased more than necessary. For this reason, it has become necessary to improve the thermal conductivity of Ti-containing materials that are hard phases other than the WC phase. As a result of further research, it was found that the thermal conductivity of the Ti-containing material is improved when the amount of W contained in the Ti-containing material is reduced.

That is, the cermet of the present invention comprises a hard phase composed of at least one of carbides, nitrides, carbonitrides and their mutual solid solutions of periodic table 4a, 5a, and 6a group elements, and an iron group metal as a main component. The hard phase is composed of two or three of the first hard phase, the second hard phase, and the third hard phase, and the WC phase. The hard phase contains Ti and the amount of W with respect to the metal element contained in the first hard phase is less than 10 atomic%, and the second hard phase contains Ti and the amount of W with respect to the metal element contained in the second hard phase is 10 atomic%. The third hard phase is composed of a core and a rim. The third hard phase core contains Ti, and the amount of W with respect to the metal element contained in the core of the third hard phase is less than 10 atomic%. The rim of the phase contains Ti and the metal contained in the rim of the third hard phase Has a W weight 10 atomic% or more with respect to iodine, and the area ratio V ₂ of the second hard phase in the cermet of the cross-sectional structure, the area ratio V _3R of the rim of the third hard phase in the cermet of the cross-sectional structure, cermet sectional structure The total area V ₁₂₃ of the area ratios of the first hard phase, the second hard phase, and the third hard phase in (1) is a cermet that satisfies ((V ₂ + V _3R ) / V ₁₂₃ ) <0.4.

As a result of previous studies, it has been found that the thermal conductivity of Ti-containing materials such as TiCN decreases due to solid solution of W in the Ti-containing materials. In particular, it has been found that when the amount of W with respect to the metal element contained in the Ti-containing material is 10 atomic% or more, the thermal conductivity rapidly decreases. Therefore, it is clear that in order to obtain a cermet exhibiting excellent thermal conductivity, it is preferable to decrease the Ti content with a W content of 10 atomic% or more and increase the Ti compound with a W content of less than 10 atomic%. It has become. The hard phase of the cermet of the present invention includes (1) a W amount with respect to a metal element of less than 10 atomic%, (2) a W amount with respect to a metal element of 10 atomic% or more and less than 100 atomic%, When the amount of W is 100 atomic%, (1) the core of the first hard phase and the third hard phase having a W content of less than 10 atomic% including Ti, and (2) the metal including Ti It can be classified into rims of the second hard phase and the third hard phase, and (3) WC phase, in which the W amount relative to the element is 10 atomic% or more. In the cross-sectional structure of the cermet of the present invention, the area ratio V ₂ of the second hard phase, the area ratio V _3R of the rim in the third hard phase, and the areas of the first hard phase, the second hard phase, and the third hard phase. If the total rate V ₁₂₃ is ((V ₂ + V _3R ) / V ₁₂₃ ) <0.4, defects due to thermal shock are reduced and the tool life is increased. On the other hand, if ((V ₂ + V _3R ) / V ₁₂₃ ) ≧ 0.4, defects are likely to occur and sufficient performance is not exhibited.

Ti and W are contained in the rim of the second hard phase and the third hard phase, but it is also preferable to include periodic table 4a, 5a, 6a elements other than Ti and W for toughening. Further, Ti is contained in the cores of the first hard phase and the third hard phase, but it is also preferable to contain periodic table 4a, 5a, 6a elements other than Ti for toughening.

When the amount of W with respect to the metal element contained in the first hard phase is less than 5 atomic%, the thermal conductivity is further increased and the heat resistance is improved, and when the amount of W is less than 1 atomic%, the heat resistance can be further increased. Therefore, it is preferable. Further, if the amount of W with respect to the metal element contained in the second hard phase and the amount of W with respect to the metal element contained in the rim of the third hard phase are 30 atomic% or less, that is, 10 to 30 atomic%, the heat resistance decreases. Is more preferable.

When the area ratio of the WC phase in the cross-sectional structure of the cermet of the present invention is 1 area% or more, toughness is improved, and when the area ratio of the WC phase exceeds 55 area%, sufficient wear resistance cannot be obtained. The area ratio of the phase is preferably 1 to 55 area%.

The binder phase of the present invention has an effect of increasing the strength of the cermet by firmly bonding the hard phase and the hard phase. In the present invention, the binder phase containing an iron group metal as a main component is an iron group metal or an iron group metal having at least one of elements of the periodic tables 4a, 5a, and 6a, Si, Al, Zn, Cu, Ru, Rh, and Re. The seed is dissolved in less than 50% by weight. In the present invention, the iron group metal represents Co, Ni, or Fe. Among them, it is more preferable that the binder phase is composed of one or two of Co and Ni because the mechanical strength is improved, and among them, the bond phase is more preferable because adhesion between the cermet and the hard film is improved. . In addition, it is preferable to dissolve less than 50% by weight of the periodic table 4a, 5a, and 6a group elements in the iron group metal of the binder phase in order to dissolve the hard phase component in the binder phase or improve the characteristics of the binder phase. If the iron group metal in the binder phase contains less than 50% by weight of Si, Al, Zn, Cu, it is preferable because the sinterability is improved. Further, it is preferable to contain 30% by weight or less of Ru, Rh, and Re in the iron group metal of the binder phase because the wear resistance is improved.

In the cross-sectional structure of the cermet of the present invention, when the area ratio of the binder phase is less than 3% by area and the area ratio of the hard phase exceeds 97% by area, sufficient toughness cannot be imparted to the cermet of the present invention, When the area ratio of the phase exceeds 20 area% and the area ratio of the hard phase is less than 80 area%, sufficient wear resistance cannot be obtained. Therefore, the area ratio of the binder phase is preferably 3 to 20 area%, and the area ratio of the hard phase is preferably 80 to 97 area%.

The surface of the cermet of the present invention is coated with a hard film such as periodic table 4a, 5a, 6a group element, Al, Si oxide, carbide, nitride and their mutual solid solution, hard carbon film by CVD method or PVD method. The coated cermet is further excellent in wear resistance. Specific examples of the hard film include TiN, TiC, TiCN, TiAlN, TiSiN, AlCrN, Al ₂ O ₃ , diamond, diamond-like carbon (DLC), and the like. When the total film thickness of the hard film is 0.1 μm or more, the wear resistance is improved, and when it exceeds 30 μm, the chipping resistance is decreased. Therefore, 0.1 to 30 μm is preferable.

The cermet of the present invention includes, for example, TiC and TiCN powder, WC powder, periodic table 4a, 5a, and 6a group carbides, nitrides, carbonitrides and their mutual solid solution powders, and iron group metal powders. A mixture obtained by mixing so as to have a predetermined composition,
(A) raising the temperature from normal temperature to a first heating temperature of 1200 to 1300 ° C. in a non-oxidizing atmosphere;
(B) a step of holding at a first heating temperature of 1200 to 1300 ° C. in a nitrogen and argon mixed atmosphere of 20 Torr or more for 30 minutes or more;
(C) When the temperature is raised from a first heating temperature of 1200 to 1300 ° C. to a second heating temperature of 1420 to 1600 ° C., a non-oxidizing atmosphere of 5 Torr or less is held for 5 minutes or more, and then the temperature is raised in a nitrogen atmosphere of 10 Torr or more Process,
(D) It can obtain by the manufacturing method of a cermet including the process hold | maintained by the 2nd heating temperature of 1420-1600 degreeC in the nitrogen atmosphere of a pressure of 10 Torr or more, and the process of (E) cooling.

In step (A), the mixture is heated in a non-oxidizing atmosphere to prevent oxidation of the mixture. Specific examples of the non-oxidizing atmosphere include a vacuum, a nitrogen atmosphere, an inert gas atmosphere, and a hydrogen atmosphere. The pressure of the atmosphere in the step (B) is preferably 20 Torr or more, whereby the amount of nitrogen in the sintered body and the surface portion can be made equal. Further, in the step (C), the sinterability can be enhanced by holding for 5 minutes or more in a non-oxidizing atmosphere of 5 Torr or less. The pressure of the nitrogen atmosphere in the steps (C) and (D) is preferably 10 Torr or more, whereby the second hard phase can be reduced. In addition, since the sinterability of a cermet will fall when the pressure of nitrogen atmosphere exceeds 300 Torr, it is preferable that the pressure of nitrogen atmosphere is 10-300 Torr.

The following method is mentioned as a specific manufacturing method of the cermet of this invention. A TiCN powder, a WC powder, carbides, nitrides, carbonitrides of these periodic table elements 4a, 5a, and 6a and their mutual solid solution powders, and iron group metal powders are prepared. These powders are weighed to a predetermined weight ratio, mixed with a solvent in a wet ball mill, and after mixing, the solvent is evaporated to dry the mixture. A molding wax such as paraffin is added to the obtained mixture to form a predetermined shape. Examples of the molding method include press molding, extrusion molding, and injection molding. The molded mixture is placed in a sintering furnace and heated to 350 to 450 ° C. in vacuum to remove the wax, and then heated from 450 ° C. to 1200 to 1300 ° C. in the vacuum or in a nitrogen atmosphere. After being warmed and held in a mixed atmosphere of nitrogen and argon of 50 Torr for 60 minutes, the mixture is heated from a first heating temperature of 1200 to 1300 ° C. to a second heating temperature of 1420 to 1600 ° C. in a non-oxidizing atmosphere of 1 Torr for 20 minutes. After that, the temperature is raised in a nitrogen atmosphere at a pressure of 10 Torr or higher, and held in a nitrogen atmosphere at a second heating temperature of 1420 to 1600 ° C. for 10 to 60 minutes. Then, it cools from 1220-1600 degreeC 2nd heating temperature to normal temperature.

The coated cermet of the present invention can be obtained by coating the surface of the cermet of the present invention with a hard film by a conventional CVD method or PVD method.

Since the cermet and coated cermet of the present invention are excellent in wear resistance and fracture resistance, they exhibit excellent cutting performance when used as a cutting tool. Therefore, when the cermet and the coated cermet of the present invention are used as a cutting tool, the tool life can be improved as compared with the conventional case.

The cermet and coated cermet of the present invention are excellent in wear resistance and fracture resistance, and when used in a tool, an effect of extending the tool life can be obtained.

As cermet raw material powder, TiC with an average particle size of 1.4 μm, Ti (C _0.5 N _0.5 ) powder with an average particle size of 1.5 μm, Ti (C _0.3 N _0.7 ) powder with an average particle size of 1.5 μm, average particle size 1.7 μm (Ti _0.92 Nb _0.05 Zr _0.01 W _0.02 ) (C _0.5 N _0.5 ) powder, average particle size 1.7 μm (Ti _0.91 Ta _0.05 W _0.04 ) (C _0.5 N _0.5 ) powder, average particle size 1. 6 μm (Ti _0.82 Nb _0.09 W _0.09 ) (C _0.5 N _0.5 ) powder, average particle size 1.5 μm (W _0.5 Ti _0.2 Ta _0.3 ) C powder, average particle size 1.5 μm WC powder, average particle size 1 .5 μm TaC powder, NbC powder with an average particle size of 1.5 μm, Mo ₂ C powder with an average particle size of 1.5 μm, Cr ₃ C ₂ powder with an average particle size of 1.6 μm, VC powder with an average particle size of 1.1 μm ZrC powder having an average particle size of 1.0 μm, HfC powder having an average particle size of 1.2 μm, Co powder having an average particle size of 1.3 μm, an average particle size of 1. We were prepared Ni powder of μm. Using these, the blending composition shown in Table 1 was weighed.

After the weighed mixed powder was mixed and pulverized by a wet ball mill, the solvent was evaporated to dry the mixture. Paraffin was added to the dried mixture and press molded. Here, for inventions 1 to 8, the press-molded mixture was put in a sintering furnace, and the temperature was gradually raised from room temperature to 450 ° C. in a vacuum to evaporate paraffin, and from 450 ° C. in vacuum. The temperature is raised to a first heating temperature of 1250 ° C., held in a mixed atmosphere of nitrogen and argon of 50 Torr for 60 minutes, and then the mixture is heated from a first heating temperature of 1250 ° C. to a second heating temperature of 1500 ° C. Then, after maintaining in a non-oxidizing atmosphere of 1 Torr for 20 minutes, the temperature was raised in a nitrogen atmosphere of 150 Torr, held in a nitrogen atmosphere of the same pressure at a second heating temperature of 1500 ° C. for 60 minutes, and cooled to room temperature. On the other hand, for the comparative products 1 to 4, the press-molded mixture was put in a sintering furnace, the temperature was gradually raised from room temperature to 450 ° C. in vacuum to evaporate paraffin, and then 450 ° C. to 1280 in vacuum. The temperature was raised to ° C. Furthermore, the temperature was raised from 1280 ° C. to 1480 ° C. in a vacuum, and held at 1480 ° C. in a vacuum for 50 minutes. Then, it cooled from 1480 degreeC to normal temperature in the vacuum.

The cross-sectional structure inside the obtained cermet was observed with a scanning electron microscope, and using the EDS attached to the scanning electron microscope, the W amount of the core and rim of the first hard phase, the second hard phase, and the third hard phase were measured. analyzed. Furthermore, the area% of each phase including the WC phase and the binder phase was measured. These results are shown in Tables 2 and 3. V _WC is the area% of the WC phase, V ₁ is the area% of the first hard phase, V ₂ is the area% of the second hard phase, V _3C is the area% of the core of the third hard phase, and V _3R is the third hard phase Rim area%, V ₁₂₃ is the total sum of the first hard phase, second hard phase, and third hard phase area% (V ₁₂₃ = V ₁ + V ₂ + V _3C + V _3R ), V _b is the binder phase Area%, C _1W is the atomic% of the W amount relative to the metal element contained in the first hard phase, C _2W is the atomic percent of the W amount relative to the metal element contained in the second hard phase, and C _3CW is the core of the third hard phase The atomic% of the W amount with respect to the metal element contained in C, and C _3RW represents the atomic% of the W amount with respect to the metal element contained in the rim of the third hard phase. The values of (V ₂ + V _3R ) / V ₁₂₃ determined from V ₂ , V _3R and V ₁₂₃ are also shown in Table 2.

Moreover, the component contained in each phase of cermet was analyzed using EDS attached to a scanning electron microscope. The results are shown in Table 4. In addition, about the component contained in a binder phase, the element of 50 weight% or more with respect to the whole binder phase was made into a main component, and the element of less than 50 weight% with respect to the whole binder phase was made into the trace component. Further, when two or more kinds of iron group elements are contained in the binder phase, the iron group elements are used as the main component if the total of iron group elements is 50% by weight or more with respect to the whole binder phase.

The produced cermet was ground and honed and processed into an ISO standard SNGN120408 shape. Further, TiAlN having a thickness of 2.5 μm was coated by the PVD method to obtain coated cermets of Invention products 1 to 8 and Comparative products 1 to 4. In addition, the cermet base material of Invention 7 has a film configuration (base material side) average film thickness 0.2 μm TiN−average film thickness 2.0 μm Ti (C, N) −average film thickness 0.6 μm Al ₂ O ₃ −average film Invention 9 was obtained by coating a hard film having a thickness of 0.2 μm TiN (outermost surface side) (average total film thickness of 3 μm) by the CVD method. Cutting tests 1 and 2 were performed using the obtained coated cermet.

[Cutting test 1]
Fracture resistance evaluation test sample shape: SNGN120408
Work material: S40C (shape: substantially cylindrical shape with four grooves in a cylinder)
Cutting speed: 160 m / min
Cutting depth: 2.0mm
Feed amount: 0.25mm / rev
Atmosphere: Number of wet cutting tests: 3 times Judgment criteria of life: The number of impacts until chipping is regarded as the life. In addition, a test is complete | finished at that time, when it does not lose | delete by the frequency | count of impact reaching 25000 times.

Table 5 shows the results of the cutting test 1.

[Cutting test 2]
Wear resistance evaluation test sample shape: SNGN120408
Work material: S40C (shape: cylinder)
Cutting speed: 200 m / min
Cutting depth: 2.0mm
Feed amount: 0.25mm / rev
Atmosphere: Criteria for wet cutting life: Life is defined as when it is missing or when the maximum flank wear amount V _Bmax is 0.3 mm or more.

Table 6 shows the results of the cutting test 2.

As shown in Table 6, the processing time of the inventive product was 24 minutes or longer, and the processing time of the comparative product was 20 minutes 20 seconds or shorter. It can be seen that the inventive product is superior in cutting performance to the comparative product.

The results of cutting test 1 and cutting test 2 were scored. That is, with respect to the number of impacts in the cutting test 1, 25000 times or more were 3 points, 20000 times or more were 2 points, 15000 times or more were 1 point, and less than 15000 times were 0 points, and the results from the 1st to the 3rd time were averaged. . Moreover, about the processing time of the cutting test 2, 30 minutes or more was made into 3 points | pieces, 20 minutes or more and less than 30 minutes were made into 2 points | pieces, and 10 minutes or more and less than 20 minutes made 1 point | pieces. The average value of the score of the cutting test 1 and the score of the cutting test 2 were totaled, and the value was used as a result of the comprehensive evaluation. The larger the score, the better the cutting performance. The obtained comprehensive evaluation results are shown in Table 7.

As shown in Table 7, it can be seen that the average value of the cutting test 1 of the invention is 2 to 3 points and is excellent in fracture resistance. The results of the cutting test 2 of the invention product are 2 to 3 points, and it is understood that the wear resistance is excellent. Invention products with excellent balance between fracture resistance and wear resistance have a high score of 4.0 to 5.0 in the overall evaluation. Comparative products have lower overall evaluation scores than invention products. This indicates that the overall cutting performance is inferior to that of the invention. For example, the comparative product 1 showed 2 points in the cutting test 2 and excellent wear resistance, but the average value of the cutting test 1 was 1.3 points, and the overall evaluation was 3.3 points. For the comparative product 4, the cutting test 1 and the cutting test 2 were both 1.0 points, and the overall evaluation was 2.0 points.

The same cermet as the cermet base material of invention products 4 and 5 before coating in Example 1 and the cermet base material of comparative products 1 and 4 were prepared, and ground and honed, and processed into an ISO standard TNGN160408 shape. The cutting test 3 was performed by using these as the cermets of the inventive products 10 and 11, and the comparative products 5 and 6, respectively, without being coated. Table 8 shows the sample contents.

[Cutting test 3]
Wear resistance evaluation test sample shape: TNGN160408
Work material: S40C (shape: cylindrical)
Cutting speed: 100 m / min
Cutting depth: 2.0mm
Feed amount: 0.25mm / rev
Atmosphere: Criteria for dry cutting life: 10 corners are cut for a maximum of 15 minutes and broken, or the maximum flank wear amount V _Bmax is 0.3 mm or more.

Table 9 shows the results of the cutting test 3.

It can be seen from Table 9 that the cermets of the inventive products 10 and 11 are superior in fracture resistance and wear resistance to the cermets of the comparative products 5 and 6.

Claims (6)

It was composed of a hard phase composed of at least one of carbides, nitrides, carbonitrides and their mutual solid solutions of the periodic table 4a, 5a, 6a group elements and a binder phase mainly composed of iron group metals. In the cermet, the hard phase is composed of two or three of the first hard phase, the second hard phase, and the third hard phase, and the WC phase, and the first hard phase includes Ti and the first hard phase. The amount of W with respect to the metal element contained in the hard phase is less than 10 atomic%, the second hard phase contains Ti, the amount of W with respect to the metal element contained in the second hard phase is 10 atomic% or more, and the third hard phase Is composed of a core and a rim, and the third hard phase core contains Ti, and the amount of W with respect to the metal element contained in the third hard phase core is less than 10 atomic%, and the third hard phase rim contains Ti. The amount of W with respect to the metal element contained in the rim of 3 hard phases is 10 atomic% or more There, an area ratio V ₂ of the second hard phase in the cermet of the cross-sectional structure, the area ratio V _3R of the rim of the third hard phase in the cermet of the cross-sectional structure, the first hard phase in the cermet of the cross-sectional structure and the second hard phase And the total area ratio V ₁₂₃ of the third hard phase is a cermet that satisfies ((V ₂ + V _3R ) / V ₁₂₃ ) <0.4. The cermet according to claim 1, wherein the amount of W with respect to the metal element contained in the first hard phase is less than 5 atomic%. The cermet according to claim 1 or 2, wherein the amount of W with respect to the metal element contained in the first hard phase is less than 1 atomic%. The total amount of W with respect to the metal elements contained in the second hard phase is 10 to 30 atomic%, and the total amount of W with respect to the metal elements contained in the rim of the third hard phase is 10 to 30 atomic%. The cermet of any one of -3. The cermet according to any one of claims 1 to 4, wherein the area ratio of the WC phase in the cross-sectional structure of the cermet is 1 to 55 area%. The coated cermet which coat | covered the hard film | membrane on the surface of the cermet of any one of Claims 1-5.