JP5213326B2 - cermet - Google Patents

Description

  The present invention relates to a cermet suitable for cutting tools, wear-resistant members, and the like.

  At present, cermets mainly composed of Ti are widely used as members that require wear resistance, slidability, and fracture resistance, such as cutting tools, wear-resistant members, and sliding members.

  For example, in Patent Document 1, type I particles made of TiCN or the like (carbonitride of a transition metal of Group 5 transition metal) and Ti and other W metals including Group 4, 5, 6 metals of the periodic table are included. A cermet containing two types of hard phases of type II particles having a large amount at the core and a small amount at the periphery is disclosed.

Patent Document 2 discloses a cermet in which a surface area of a black first hard phase having an area ratio of 80% by area or more exists at a depth of 5 μm or less on the pole surface of the cermet, and the wear resistance of the cermet is disclosed. It is described that can be maintained.
Japanese Patent Laid-Open No. 2-190438 JP 2005-213599 A

  However, even with the structure of the cermet as in Patent Documents 1 and 2, the wear resistance and fracture resistance are still insufficient, and particularly the wear resistance of the cermet surface that becomes the cutting edge when used as a cutting tool and It has been desired to improve the fracture resistance.

  Therefore, the cermet of the present invention is for solving the above-mentioned problems, and the object thereof is to provide a cermet having high wear resistance and fracture resistance on the surface of the cermet.

  The cermet of the present invention is a cermet in which a hard phase composed of a nitride or carbonitride of a periodic table 4, 5 and 6 metal mainly composed of Ti is bonded with a bonded phase mainly composed of Co or Ni. When the cross-sectional structure is observed, the average particle diameter of the hard phase in the interior is 0.05 to 1 μm, and the hard phase is composed of a first hard phase mainly composed of TiCN, and periodic tables 4 and 5. And a second hard phase of a composite carbonitride solid solution of at least one group 6 metal and Ti, and the ratio of the first hard phase is 70% by area or more on the surface, the average of the first hard phase A surface region having a particle size smaller than the average particle size of the first hard phase inside is present.

  Here, in the above-described configuration, the second hard phase contains at least one of W and Nb, and at the center of the second hard phase, the content of at least one of W and Nb is large. It is desirable that the content of at least one of W and Nb is small in the outer peripheral portion.

  Moreover, in the said structure, it is desirable for (total amount of W and Nb) / (total amount of the whole metal element) in the outer peripheral part of a said 2nd hard phase to be 2-20 atomic%.

Furthermore, when observing the sectional structure, the average particle size of the first hard phase in the interior and a _i, when the average particle diameter of the second hard phase was b _i, a ratio between a _i and b _i It is desirable that (b _i / a _i ) is 2-8.

Further, when the cross-sectional structure is observed, when the average area occupied by the first hard phase with respect to the entire hard phase in the inside is A _i and the average area occupied by the second hard phase is B _i , A _i ratio of _{B i (B i / a i} ) it is desirable that 1.5 to 5.

  Furthermore, it is desirable that the surface region exists with a thickness of 0.2 to 5 μm from the surface.

Further, when observing the cross-sectional structure, in between the inner and the surface area, the average area of the first hard phase to the entire said hard phase occupies the A _m, an average area of the second hard phase occupies B when the _m, it is desirable that a large intermediate region than the ratio _(B m / _{a m)} is the ratio _{(B i} / _a i) of _{a m} and _{B m} are present.

  Furthermore, it is desirable that the intermediate region exists with a thickness of 30 to 300 μm.

  In the cermet of the present invention, when the cross-sectional structure is observed, the average particle size of the hard phase in the interior is 0.05 to 1 μm, and the hard phase includes a first hard phase mainly composed of TiCN, and a period. Table 4 consists of a second hard phase of a composite carbonitride solid solution of at least one of Group 4, 5 and 6 metals and Ti, and the ratio of the first hard phase to the surface is 70 area% or more A surface region in which the average particle size of the first hard phase is smaller than the average particle size of the first hard phase in the inside exists. As a result, the wear resistance is excellent, and even when a crack is generated in the surface region, the effect of suppressing the progress of the crack is high, and the wear resistance and fracture resistance are excellent.

  Here, in the above-described configuration, the second hard phase contains at least one of W and Nb, and at the center of the second hard phase, the content of at least one of W and Nb is large. The fact that the content of at least one of W and Nb is small in the outer peripheral portion, the toughness is improved in the central portion of the second hard phase and the impact resistance is increased, and the hardness is improved in the outer peripheral portion of the second hard phase. This is desirable in terms of improving plastic deformability.

  Moreover, in the said structure, it is 2-20 atomic% that (W and Nb and total amount) / (total amount of the whole metal element) in the outer periphery of a said 2nd hard phase improves the thermal conductivity of a cermet. This is desirable because the thermal shock resistance is improved.

Furthermore, when observing the sectional structure, the average particle size of the first hard phase in the interior and a _i, when the average particle diameter of the second hard phase was b _i, a ratio between a _i and b _i It is desirable that (b _i / a _i ) is 2 to 8 in that the second hard phase effectively contributes to heat propagation, the thermal conductivity of the cermet is improved, and the thermal shock resistance of the cermet is improved.

Further, when the cross-sectional structure is observed, when the average area occupied by the first hard phase with respect to the entire hard phase in the inside is A _i and the average area occupied by the second hard phase is B _i , A _i The ratio of B _i to B _i (B _i / A _i ) is 1.5 to 5, the second hard phase effectively contributes to heat propagation, the thermal conductivity of the cermet is improved, and the thermal shock resistance of the cermet Is desirable in terms of improvement.

  Furthermore, since the surface region is present at a thickness of 0.2 to 5 μm from the surface, the abrasion resistance on the cermet surface is high, and the thermal shock resistance of the cermet can be maintained without significantly reducing the thermal shock resistance. Is desirable.

Further, when observing the cross-sectional structure, in between the inner and the surface area, the average area of the first hard phase to the entire said hard phase occupies the A _m, an average area of the second hard phase occupies B when the _m, the greater the intermediate region than the ratio _(B m / _{a m)} is the ratio _{(B i} / _a i) of _{a m} and _{B m} are present, enhance the thermal conductivity in the vicinity of the cermet surface It is desirable to improve the thermal shock resistance of the cermet.

  Furthermore, it is desirable for the intermediate region to have a thickness of 30 to 300 μm in order to increase the thermal conductivity in the vicinity of the cermet surface and improve the thermal shock resistance of the cermet.

  An example of the cermet of the present invention will be described based on a scanning electron micrograph of (a) the vicinity of the surface and (b) the inside of FIG.

  As shown in FIG. 1 (a), the cermet 1 of the present invention is composed of a hard phase 2 composed of a nitride or carbonitride of a periodic table 4, 5 and 6 metal having Ti as a main component, and Co or Ni as a main component. When the cross-sectional structure is observed, the average particle diameter of the hard phase 2 in the interior is 0.05 to 1 μm, and the hard phase 2 is a first containing TiCN as a main component. It consists of the hard phase 4 and the second hard phase 5 of the composite carbonitride solid solution of Ti and at least one of Group 4, 5 and 6 metals of the periodic table, and the ratio of the first hard phase 4 is 70 on the surface. A surface region 7 having an area% or more and a smaller average particle size of the first hard phase 4 than the average particle size of the first hard phase 4 is present. As a result, the wear resistance is excellent, and even when a crack is generated in the surface region, the effect of suppressing the progress of the crack is high, and the wear resistance and fracture resistance are excellent.

  That is, the cermet 1 whose average particle size of the hard phase 2 is smaller than 0.05 μm cannot be produced by the current technology, and when the average particle size of the hard phase 2 exceeds 1 μm, the hardness and strength of the cermet 1 are lowered. Thus, when the cermet 1 is used as a cutting tool or a wear-resistant member, the surface of the cermet 1 is likely to be deformed.

  Here, when the cross-sectional structure is observed with a scanning electron microscope, the first hard phase 4 is observed as black particles or particles having a cored structure in which a grayish white peripheral portion exists around the black core portion. Is done. On the other hand, the second hard phase 4 is observed as grayish white particles or particles having a cored structure in which a grayish white peripheral portion exists around the white core portion. The grayish white color may appear to be a color tone close to white or may be a color tone close to gray depending on the conditions of photography.

Further, in this configuration, when the average particle diameter of the first hard phase 4 in the surface region 7 and a _s, which was defined as an average particle size a _i of the first hard phase 4 in the interior, the ratio of a _s and a _i ( a _s / a _i ) is preferably 0.6 to 0.95 in that the hardness and chipping resistance on the surface of the cermet 1 can be improved. A range of _(a s / _{a i)} is from 0.65 to 0.87.

  In the above configuration, the second hard phase 5 includes at least one of W and Nb, and at the center of the second hard phase 5, the content of at least one of W and Nb is large. The fact that the content of at least one of W and Nb is small in the outer peripheral portion improves the toughness and the impact resistance at the central portion of the second hard phase 5 and the hardness at the outer peripheral portion of the second hard phase 5. It is desirable in terms of improving the plastic deformability.

  In addition, (W and Nb and the total amount) / (total amount of the entire metal element) in the outer periphery of the second hard phase 5 is 2 to 20 atomic%, so that the thermal conductivity of the cermet 1 is improved and the thermal shock is applied. This is desirable because of improved properties. A particularly desirable range of (total amount of W and Nb) / (total amount of all metal elements) is 30 to 42 atomic%.

Furthermore, when observing the cross section structure, an average particle diameter of the first hard phase 4 in the interior and a _i, when the average particle diameter of the second hard phase 5 was b _i, a ratio between a _i and b _i The point that (b _i / a _i ) is 2 to 8, the second hard phase 5 effectively contributes to heat propagation, the thermal conductivity of the cermet 1 is improved, and the thermal shock resistance of the cermet 1 is improved. Is desirable.

Further, when the cross-sectional structure is observed, when the average area occupied by the first hard phase 4 with respect to the entire hard phase 2 inside is A _i and the average area occupied by the second hard phase 5 is B _i , A _i ratio of _{B i (B i / a i} ) that is 1.5 to 5, and a second hard phase 5 effectively contributes to thermal propagation improves the thermal conductivity of the cermet 1, the cermet 1 It is desirable in terms of improving thermal shock resistance.

  Further, the surface region 7 having a thickness of 0.2 to 5 μm from the surface has high wear resistance on the surface of the cermet 1 and the thermal shock resistance of the cermet 1 without significantly reducing the thermal shock resistance. This is desirable because it can be maintained. A particularly desirable range of the thickness of the surface region 7 is 0.5 to 3 μm from the surface.

Further, when observing the cross-sectional structure, in between the inner and the surface area 7, the average area of the first hard phase 4 to the entire hard phase 2 is occupied and A _m, an average area of second hard phase 5 occupied B _{It is} assumed that there is an intermediate region 8 in which the ratio (B _m / A _m ) between A _m and B _m is larger than the ratio (B _i / A _i ), where _m is the heat conduction in the vicinity of the surface of the cermet 1. It is desirable to improve the thermal shock resistance of the cermet 1 by increasing the properties. A particularly desirable range of the ratio (B _m / A _m ) is 3 to 10, and a desirable range of the ratio (B _m / A _m ) / ratio (B _i / A _i ) is 1.2 to 2.3.

In the intermediate region 8, when the average particle size of the second hard phase 5 in the intermediate region 8 is b _m , the ratio (b _m / b _i) with the average particle size b _i of the second hard phase 5 inside. ) Is 1.1 to 2, the second hard phase 5 in the intermediate region 8 effectively contributes to the heat propagation, the thermal conductivity of the cermet 1 is improved, and the thermal shock resistance of the cermet 1 is improved. Is desirable.

  Furthermore, it is desirable for the intermediate region 8 to be present at a thickness of 30 to 300 μm in order to increase the thermal conductivity in the vicinity of the surface of the cermet 1 and improve the thermal shock resistance of the cermet 1.

  Here, it is desirable that the total content of the nitrides or carbonitrides of the periodic tables 4, 5 and 6 metals mainly composed of Ti which forms the hard phase contained in the cermet 1 is 70 to 96% by mass. In particular, it is preferably 85 to 95% by mass in terms of improvement in wear resistance. On the other hand, when the content of the binder phase 3 is 4 to 14% by mass, the balance between hardness and toughness of the substrate is excellent. Moreover, as a binder phase, it is desirable for containing Co 65 mass% or more with respect to the total amount of an iron group metal, in order to improve the thermal shock resistance of a cutting tool. In addition, in order to maintain the favorable sinterability of cermet 1 so that the burnt surface of cermet 1 becomes a smooth surface, 5-50 mass%, especially 10-35 mass% of Ni as an iron group metal is used. It is desirable to make it contain in a ratio.

  In addition, the measurement of the particle size of the hard phase 2 in this invention is measured according to the measuring method of the average particle size of the cemented carbide prescribed | regulated to CIS-019D-2005. At this time, in the case where the hard phase 2 has a cored structure, the outer edge of the peripheral part including the core part and the peripheral part is measured as one hard phase.

(Production method)
Next, the manufacturing method of the tool mentioned above is demonstrated.

  First, TiCN powder having an average particle size of 0.1 to 1.2 μm, especially 0.2 to 0.9 μm, TiN powder having an average particle size of 0.1 to 2 μm, carbide powder of other metals described above, and nitride powder Alternatively, a mixed powder obtained by mixing any one of carbonitride powders and Co powder or Ni powder is prepared.

  According to the present invention, with respect to the total content of carbon and nitrogen in the TiCN raw material powder, the nitrogen content is in the range of 0.45 to 0.50, and the carbon content contained in the WC raw material powder. It is important to control the range from 6.30 to 6.40. If the amount of carbon and the amount of nitrogen deviate from these ranges, a predetermined surface region cannot be formed on the surface of the cermet 1. A desirable range of the nitrogen content ratio in the TiCN raw material powder is 0.47 to 0.50, and a particularly desirable range of the amount of carbon contained in the WC raw material powder is 6.31 to 6.35.

  Further, the average particle size of the iron group metal powder, that is, Co powder or Ni powder is preferably 2 μm or less, particularly 0.05 to 1.5 μm, in order to improve the sinterability of the cermet substrate. Furthermore, it is desirable to use a solid solution powder containing Co and Ni in a predetermined ratio as the binding metal raw material powder from the viewpoint of further improving the sinterability. The average particle size of other raw material powders is preferably 0.05 to 3 μm.

  And a binder is added to this mixed powder, and it shape | molds in a predetermined shape by well-known shaping | molding methods, such as press molding, extrusion molding, and injection molding.

  Next, according to the present invention, the above-mentioned cemented carbide having a predetermined structure can be produced by firing under the following conditions. As firing conditions, (a) after raising the temperature from 1050 to 1250 ° C. at a firing temperature A of 5 to 15 ° C./min, the firing temperature A to 1275 to 1375 ° C. to a firing temperature B of 0.1 to 3 ° C. / (B) Then, the temperature is increased from 4 to 15 ° C./minute from the firing temperature B to 1500 to 1600 ° C. in an atmosphere having a nitrogen partial pressure of 30 to 2000 Pa. After firing for 0.5 to 2 hours in an atmosphere having a nitrogen partial pressure of 30 to 2500 Pa, (d) the temperature is lowered in an atmosphere in which the nitrogen partial pressure is raised to a higher gas pressure than during firing at 500 to 5000 Pa.

  According to the present invention, the cermet 1 having the above-described structure can be produced by controlling the temperature rising pattern during the firing and the timing of introducing a predetermined amount of inert gas.

  Then, if desired, a coating layer is formed on the surface of the cermet 1. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method.

TiCN powder with an average particle size of 0.6 μm and an average particle size of 1.1 μm as shown in Table 1 as measured by the microtrack method (Table 1 shows the ratio of carbon to nitrogen as the CN ratio) The WC powder having the carbon amount in Table 1, the TiN powder having an average particle diameter of 1.5 μm, the TaC powder having an average particle diameter of 2 μm, the NbC powder having an average particle diameter of 1.5 μm, the ZrC powder having an average particle diameter of 1.8 μm, and the average particle Using a stainless steel ball mill and carbide balls, a mixed powder prepared by adjusting a VC powder having a diameter of 1.0 μm, a Ni powder having an average particle diameter of 2.4 μm, and a Co powder having an average particle diameter of 1.9 μm at a ratio shown in Table 1 is used. The mixture was wet-mixed with isopropyl alcohol (IPA), added with 3% by weight of paraffin, mixed, pressed into a tool shape of CNMG120408 at 200 MPa, and fired under the firing conditions shown in Table 2.

The obtained cutting tool was observed with a scanning electron microscope (SEM), and an image analysis was performed in a region of 8 μm × 8 μm using commercially available image analysis software for each of the surface and the interior at a 10000 × magnification. Then, the presence state of the hard phase, the surface region, and the presence of the intermediate region were confirmed, and the average particle diameters thereof were measured to calculate the ratio thereof. The results are shown in Table 3.

  Further, the composition of the central portion and the outer peripheral portion of the second hard phase inside the cermet was quantified by line analysis of Auger electron spectroscopy (AES). Note that the measurement conditions of Auger electron spectroscopy (AES) were measured with an acceleration voltage of 20 KeV, a sample current of 10 nA, and a sample tilt angle of 30 degrees. And the ratio of the total content of W and Nb with respect to the total amount of periodic table 4, 5 and 6 group metal was computed. In addition, about the calculation of a ratio, the average value about five arbitrary 2nd hard phases was taken. The results are shown in Table 4.

  Next, a cutting test was performed using the obtained cutting tool under the following cutting conditions. The results are shown together in Table 4.

(Abrasion resistance test)
Work material: SCM435
Cutting speed: 250 m / min
Feed: 0.20mm / rev
Cutting depth: 1.0mm
Cutting condition: wet (use water-soluble cutting fluid)
Evaluation method: Time until the wear amount reaches 0.2 mm (fracture resistance test)
Work material: SCM440H
Cutting speed: 100 m / min
Feed: 0.25mm / rev
Cutting depth: 1.0mm
Cutting condition: Dry evaluation method: Number of impacts until breakage

  From Tables 1-4, the sample No. using the WC raw material powder whose carbon amount exceeds 6.40. In No. 8, the average particle size of the hard phase exceeded 1 μm, and the sample No. using a WC raw material powder having a carbon content less than 6.30 was used. In No. 9, the surface region of the cermet was not formed, and in all cases, the wear resistance of the cutting edge in cutting performance was low. In addition, the sample gas No. in which the atmospheric gas pressure when firing at the firing temperature C and the atmospheric gas pressure during cooling are the same. In No. 10, the average particle size of the first hard phase in the surface region was the same as the average particle size of the first hard phase inside, and the chipping resistance was inferior in cutting performance. In addition, in the cooling step after firing, the sample No. 11 and the sample No. 1 fired in a vacuum atmosphere when firing at the firing temperature C and firing at the firing temperature C. In No. 15, the surface region was not formed and the wear resistance was poor. Furthermore, sample No. of TiCN raw material powder having a nitrogen content ratio of less than 0.45. In No. 13, the average particle size of the hard phase exceeded 1 μm, and the wear resistance of the cutting edge in cutting performance was low. Sample No. of TiCN raw material powder having a nitrogen content ratio exceeding 0.50. In No. 16, many voids were generated on the cermet surface, and the wear resistance of the cutting edge was low.

  On the other hand, sample no. 1 to 7, 12, 14, 17, and 18 exhibited excellent wear resistance and good fracture resistance, and as a result, the tool life was long.

Sample No. 1 prepared in Example 1 was used. A cermet having a cutting tool shape of No. 7 was processed with a diamond grindstone, and a coating layer was formed by an arc ion plating method. Specifically, the substrate was set in an arc ion plating apparatus and heated to 500 ° C., and then a coating layer of Ti _0.3 Al _0.5 W _0.2 N was formed. The film forming conditions were a mixed gas of nitrogen gas and argon gas in an atmosphere having a total pressure of 2.5 Pa, an arc current of 100 A, a bias voltage of 50 V, and a heating temperature of 500 ° C. In addition, the layer thickness of the coating layer was 1.0 μm.

  A cutting test was performed under the same cutting conditions as in Example 1 using the obtained cutting tool.

  As a result, the time until the amount of wear reached 0.2 mm after the start of cutting was as good as 80 minutes.

An example of the cermet of this invention is shown, and it is a scanning electron micrograph about (a) surface vicinity and (b) inside.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cermet 2 Hard phase 3 Bonded phase 4 1st hard phase 5 2nd hard phase 7 Surface area | region 8 Middle area | region

Claims (8)

A cermet in which a hard phase composed of a nitride or carbonitride of a periodic table 4, 5 and 6 metal containing Ti as a main component is bonded with a binder phase containing Co or Ni as a main component, and a cross-sectional structure was observed. The average particle size of the hard phase in the interior is 0.05 to 1 μm, and the hard phase is at least one of the first hard phase mainly composed of TiCN and the metals in Groups 4, 5, and 6 of the periodic table. It comprises a second hard phase of a composite carbonitride solid solution of one kind and Ti, and the ratio of the first hard phase is 70% by area or more on the surface, and the average particle size of the first hard phase is the above in the interior A cermet characterized in that a surface area smaller than the average particle diameter of the first hard phase exists.   The second hard phase contains at least one of W and Nb, and has a large content of at least one of W and Nb in the central portion of the second hard phase, and W and Nb in the outer peripheral portion of the second hard phase. The cermet according to claim 1, wherein the content of at least one is small.   3. The cermet according to claim 2, wherein (total amount of W and Nb) / (total amount of the entire metal element) in the outer peripheral portion of the second hard phase is 2 to 20 atomic%. When observing the sectional structure, the average particle size of the first hard phase in the interior and a _i, when the average particle diameter of the second hard phase was b _i, a ratio between a _i and b _i (b The cermet according to claim 2 or 3, wherein _i / _ai ) is 2-8. When observing the sectional structure, the average area of the first hard phase occupied for the entire the hard phase in the interior and A _i, when the average area of the second hard phase occupies was B _i, A _i and B _i The cermet according to claim 4, wherein the ratio (B _i / A _i ) is 1.5 to 5.   The cermet according to claim 1, wherein the surface region is present at a thickness of 0.2 to 5 μm from the surface. When observing the cross-sectional structure, in between the inner and the surface area, the average area of the first hard phase to the entire said hard phase occupies the A _m, an average area of the second hard phase occupies a B _m The cermet according to claim 5 , wherein there is an intermediate region in which a ratio (B _m / A _m ) between A _m and B _m is larger than the ratio (B _i / A _i ). The cermet according to claim 7, wherein the intermediate region has a thickness of 30 to 300 μm.