JP2009030130A - Cermet having composite surface layer and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet which extends the life of a cutting tool, by improving both of the abrasion resistance and chipping resistance thereof. <P>SOLUTION: The cermet having a composite surface layer comprises the first surface layer with an average thickness of 2 to 20 μm and the second surface layer with an average thickness of 5 to 50 μm, which are formed in a direction from a case-hardened surface toward the inside of the cermet. The first surface layer comprises: a first hard phase of a carbonitride composite containing one or more elements in Group 5a and 6a of the Periodic Table, one or more elements of Zr and Hf, and Ti; and a binder phase. The second surface layer comprises: a second hard phase of a nitride and/or a carbonitride of Zr and Hf; the first hard phase; and the binder phase. The inner part of the cermet comprises: a third hard phase having a cored structure which comprises a core part of a carbide and/or a carbonitride of Ti, and a peripheral part containing a carbonitride composite containing one or more elements in Group 5a and 6a of the Periodic Table, one or more elements of Zr and Hf, and Ti; the first hard phase; and the binder phase. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cermet having a composite surface layer that extends tool life by improving both wear resistance and chipping resistance in a wide range of cutting operations such as turning of steel and castings and milling. .

  Cermets represented by the TiCN-Mo-Ni system are frequently used because of the beautiful finish surface as well as excellent wear resistance in steel cutting. However, since the wear resistance and chipping resistance are still insufficient, further improvement is required. As the improvement means, many cermets having a gradient composition on the surface and cermet tools having a hard layer formed on the surface have been proposed.

  As a conventional gradient composition cermet tool, there is a TiCN-based cermet whose surface portion is made tougher and harder than the inside by gradually decreasing the amount of the binder phase near the surface (see, for example, Patent Documents 1 and 2). . TiCN-based cermets described in these materials are heated in a nitrogen gas atmosphere and evacuated before the end of sintering, thereby reducing the amount of binder phase near the surface and making the surface portion highly hard and wear-resistant. However, there is a problem that chipping resistance and chipping resistance are insufficient.

  Further, as a cermet tool having a hard layer formed, there is a cermet tool in which a hard layer made of only a high nitrogen content composite nitride is formed on the outermost surface by nitriding and sintering in a nitrogen gas atmosphere (for example, patents) Reference 3). Although the formed hard layer has a high hardness, the wear resistance is improved, but there is a problem that the chipping resistance is inferior because it does not contain a metal binder phase.

Japanese Patent Laid-Open No. 2-15139 JP-A-2-93036 JP-A-10-147831

  The present invention solves the above-mentioned problems, and by forming two surface layers in which the type and configuration of the hard phase is different from the inside from the burnt surface to the inside, wear resistance and anti-resistance are formed. An object of the present invention is to provide a cermet having a composite surface layer that achieves both chipping properties.

  The present inventor, for a cermet tool having a surface layer, in order to improve wear resistance and plastic deformation resistance without reducing chipping resistance, the type and configuration of hard phase particles contained in the surface layer As a result of the study on the surface of the burnt skin, it is bonded to the first hard phase of the composite carbonitride containing one or more elements in the group 5a, 6a of the periodic table, one or more elements in Zr, Hf, and Ti. A first surface layer composed of a phase, and at least one second hard phase of Zr, Hf nitride, carbonitride, and their mutual solid solution and the first surface layer are formed inside the first surface layer. A second surface layer composed of a hard phase and a binder phase is formed, and the inside of the second surface layer is made of Ti carbide or carbonitride as a core and one or more elements in the periodic table 5a, 6a group elements A composite carbonitride containing at least one of Zr and Hf and Ti is used as a peripheral part. Including a third hard phase, a first hard phase, and a binder phase having a core structure improves both wear resistance and chipping resistance, and for producing a cermet having this composite surface layer. (A) at least one of nitrides, carbonitrides and their mutual solid solutions of Zr and Hf: 5 to 25% by weight with respect to the whole hard phase forming powder, and (b) periodic table 5a, At least one of carbides, nitrides and carbonitrides of group 6a elements: 10 to 40% by weight with respect to the entire hard phase forming powder, and (c) at least one of Ti carbides and carbonitrides: hard A hard phase forming powder consisting of 35 to 85% by weight and a binder phase forming powder consisting of at least one of Co and Ni are prepared with respect to the whole phase forming powder, and the hard phase forming powder: 75 to 95% by weight And binder phase forming powder: 5 to 25% by weight When a mixture is obtained and kept in nitrogen gas at a pressure of 10 kPa or higher at a temperature of 1100 to 1300 ° C., a second hard phase is formed, and the mixture is further heated at a temperature of 1400 to 1550 ° C. The inventors have obtained knowledge that a first surface layer is formed by sintering in nitrogen gas at a pressure of 5 kPa or less, and have completed the present invention.

That is, the cermet having the composite surface layer of the present invention includes at least one hard phase of carbides, nitrides and their mutual solid solutions of the periodic table 4a, 5a, and 6a elements, and at least one of Co and Ni. In the cermet comprising a binder phase mainly composed of seeds, a first surface layer having an average thickness of 2 to 20 μm is formed from the baked skin surface of the cermet toward the inside, and the interface between the first surface layer and the second surface layer A second surface layer having an average thickness of 5 to 50 μm is formed from the inside toward the inside,
(1) The first surface layer is bonded to a first hard phase of a composite carbonitride containing one or more elements in the periodic table 5a and 6a group elements, one or more elements in Zr and Hf, and Ti. Consist of phases
(2) The second surface layer is composed of at least one second hard phase among the nitride of Zr, Hf, carbonitride, and their mutual solid solution, the first hard phase, and the binder phase.
(3) The inside of the cermet excluding the first surface layer and the second surface layer has Ti carbide and carbonitride as a core, and one or more elements in the periodic table 5a, 6a group elements and Zr, It includes a third hard phase having a core structure having a composite carbonitride containing one or more of Hf and Ti as a peripheral portion, a first hard phase, and a binder phase.

  Specific examples of the binder phase in the cermet of the present invention include at least one alloy of Co and Ni in which 20% by weight or less of Ti, Mo, W, Cr and the like are dissolved. When the amount of the binder phase is less than 5% by weight based on the whole alloy, the fracture resistance is deteriorated due to a decrease in toughness, and conversely when it exceeds 25% by weight, the hardness is decreased, resulting in wear resistance and plastic deformation. In order to reduce properties, the amount of the binder phase is preferably 5 to 25% by weight.

  The hard phase in the cermet of the present invention is composed of at least one of carbides, nitrides, and mutual solid solutions of the periodic table 4a, 5a, and 6a group elements. Specifically, (Ti, Zr, Mo) (C, N), (Ti, Zr, W) (C, N), (Ti, Zr, Nb, W, Mo) (C, N), (Ti , Hf, Ta, W, Mo) (C, N) and other solid carbonitride solid solution particles, ZrN, Zr (C, N), HfN, Ti (C, N) single particles, the core is TiC There may be mentioned cored structure particles whose peripheral part is (Ti, Nb, W) (C, N), (Ti, Zr, Ta, W, Mo) (C, N), and mixed particles thereof. . When the content of the hard phase is less than 75% by weight, the amount of the binder phase is relatively increased and the wear resistance and plastic deformation resistance are deteriorated. Since chipping property is lowered, the content of the hard phase is preferably 75 to 95% by weight. Among them, the hard phase of the present invention contains at least one of Zr, Hf nitrides, carbonitrides and their mutual solid solutions: 5 to 25% by weight with respect to the entire hard phase, periodic table 5a, At least one of the carbides, nitrides and carbonitrides of group 6a elements: 10 to 40% by weight based on the entire hard phase, and at least one of Ti carbides and carbonitrides: based on the entire hard phase More preferably, it is 35 to 85% by weight. The reason is shown below.

  When at least one of nitrides of Zr and Hf, carbonitrides and their mutual solid solutions is added as a hard phase in the cermet of the present invention, a composite surface layer is formed, and the plastic deformation resistance, Improve weldability and wear resistance. When the addition amount of at least one of the nitrides, carbonitrides, and their mutual solid solutions of Zr and Hf is less than 5% by weight based on the entire hard phase, at least one nitride and carbon of Zr and Hf It is difficult to leave the nitride particles in the second surface layer. Conversely, if the amount exceeds 25% by weight with respect to the entire hard phase, a large amount remains in the interior, so that the sinterability deteriorates. While the hardness and toughness are reduced, the hardness and toughness remain in the first surface layer, so that the content is preferably 5 to 25% by weight based on the entire hard phase.

  When at least one of the carbides, nitrides, and carbonitrides of Group 5a and 6a elements of the periodic table is added as the hard phase in the cermet of the present invention, the hardness, strength, toughness, etc. are improved and the wear resistance is improved. Improve fracture resistance, chipping resistance, plastic deformation resistance, etc. When the addition amount of at least one of carbides, nitrides, and carbonitrides of group 5a and 6a elements in the periodic table is less than 10% by weight with respect to the entire hard phase, the effect of increasing toughness is particularly small and chipping resistance is reduced. On the contrary, if the content exceeds 40% by weight with respect to the entire hard phase, the content of Ti carbide and nitride is relatively reduced and wear resistance is lowered. 10 to 40% by weight is preferable.

  When at least one of Ti carbide and carbonitride is added as the hard phase in the cermet of the present invention, hardness and wear resistance are improved. When the amount of at least one of Ti carbide and carbonitride added is less than 35% by weight with respect to the entire hard phase, the wear resistance decreases, and conversely, it exceeds 85% by weight with respect to the entire hard phase. If it becomes, since intensity | strength, toughness, and fracture resistance will fall, it is preferable in it being 35 to 85 weight% with respect to the whole hard phase.

  The baked skin surface in the cermet of the present invention means the surface after sintering, but also includes the case where the baked skin surface is subjected to surface treatment such as blasting, electrolytic treatment, and grinding treatment together with the untreated baked skin surface.

  The first surface layer in the cermet of the present invention includes a first hard phase of a composite carbonitride containing at least one of elements in the periodic table 5a and 6a group, at least one of Zr and Hf, and Ti. , And a binder phase. When the average thickness of the first surface layer is less than 2 μm, the toughness of the surface is not sufficiently improved, so that chipping is easy. Conversely, when the thickness exceeds 20 μm, the wear resistance decreases, so the average thickness is set to 2 to 20 μm. .

  The second surface layer in the cermet of the present invention comprises at least one second hard phase among the nitrides of Zr and Hf, carbonitrides, and their mutual solid solutions, the first hard phase, and the binder phase. Is. When the average thickness of the second surface layer is less than 5 μm, the effect of improving the welding resistance by the second hard phase is reduced and the wear resistance is lowered. Conversely, when the thickness exceeds 50 μm, the chipping resistance is lowered. In addition, the average thickness of the second surface layer was determined to be 5 to 50 μm.

  The inside of the cermet excluding the first surface layer and the second surface layer of the present invention is composed of Ti carbide and carbonitride as a core and one or more elements in the periodic table 5a, 6a group elements and Zr, Hf. A third hard phase having a core structure having a composite carbonitride containing at least one of the above and Ti as a peripheral portion, a first hard phase, and a binder phase. Moreover, the inside of the cermet of the present invention may include a second hard phase in addition to the first hard phase, the third hard phase, and the binder phase.

The cermet of the present invention is preferable when the content of the specific element changes depending on the positions of the first surface layer, the second surface layer, and the inside, because the excellent effect of the composite surface layer appears remarkably. The content of nitrogen contained in the first surface layer is N _S1 (% by weight), the content of nitrogen contained in the second surface layer is N _S2 (% by weight), and the content of nitrogen contained inside is N _I ( Weight%), when N _S1 , N _S2 , and N _I satisfy N _S2 > N _I > N _S1 , the first hard phase in the first surface layer having the lowest nitrogen content becomes coarse. It is preferable because the toughness is improved and the welding resistance of the second hard phase in the second surface layer having the highest nitrogen content is increased to improve the wear resistance.

Next, the periodic table 6a group element amount contained in the first surface layer is 6a _S1 (wt%), the periodic table 6a group element amount contained in the second surface layer is 6a _S2 (wt%), and included therein When the amount of group 6a element in the periodic table is expressed as 6a _I (weight%), if 6a _S1 , 6a _S2 , 6a _I satisfy 6a _S1 > 6a _I > 6a _S2 , the content of the group 6a element is the most. The first hard phase in the high first surface layer has high toughness and chipping resistance is improved, and the first hard phase in the second surface layer having the lowest content of the group 6a element has high hardness and resistance. This is preferable because the wear resistance is improved.

Furthermore, the content of at least one of Co and Ni contained in the first surface layer is BD _S1 (wt%), and the content of at least one of Co and Ni contained in the second surface layer is BD _S2 (wt%). ), When the content of at least one of Co and Ni contained therein is expressed as BD _I (% by weight), when BD _S1 , BD _S2 , BD _I satisfies BD _I > BD _S2 ≧ BD _S1 , It is preferable because the content of at least one of Co and Ni in the first surface layer is the lowest and the outermost surface is high in hardness and wear resistance is improved.

  The method for producing a cermet having a composite surface layer according to the present invention comprises (a) at least one of nitrides, carbonitrides of Zr and Hf, and their mutual solid solution: 5 to 25 with respect to the entire hard phase forming powder. (B) at least one of carbides, nitrides, and carbonitrides of Group 5a and 6a elements of the periodic table: 10 to 40% by weight based on the entire hard phase forming powder, and (c) Ti At least one of carbides and carbonitrides: a hard phase forming powder comprising 35 to 85% by weight with respect to the entire hard phase forming powder, and a binder phase forming powder comprising at least one of Co and Ni. A mixture of hard phase forming powder: 75 to 95% by weight with respect to the whole mixture and binder phase forming powder: 5 to 25% by weight with respect to the whole mixture to obtain a mixture; 10 kPa pressure at a temperature of ℃ A step of holding in nitrogen gas above the mixture is intended to include the step of sintering in a pressure 5kPa or less of the nitrogen gas at a temperature of from 1,400 to 1550 ° C..

In the production method of the present invention, when nitrides such as ZrN and HfN are used as at least one kind of powders of nitrides, carbonitrides, and their mutual solid solutions of Zr and Hf, ZrN and This is preferable because the residual amount of HfN is increased and the welding resistance is improved. Further, it is preferable to add at least one powder of carbides, nitrides, and carbonitrides of Group 5a and 6a elements of the periodic table because cored structure particles are easily formed. Specifically, Mo ₂ C, WC, TaC, NbN and the like can be mentioned. Further, it is preferable to use TiC or Ti (C, N) having a small amount of nitrogen as the Ti carbide or carbonitride powder because cored structure particles are easily formed.

  The atmosphere at the time of temperature rise and sintering in the production method of the present invention controls the partial pressure of nitrogen gas. When the temperature is raised, the powder molded body is maintained in a nitrogen gas of 10 kPa or more in a temperature range from 1100 ° C. at which nitridation of Zr, Hf, Ti becomes significant to 1300 ° C. at which the shrinkage of the powder molded body becomes significant. A high nitrogen content region is formed on the surface of the substrate. And at the time of sintering in the temperature range of 1400-1550 degreeC, it is denitrified from the outermost surface by setting it as 5 kPa or less nitrogen gas atmosphere. That is, a first surface layer having a low nitrogen content is formed on the outermost surface, and a second surface layer having a high nitrogen content is formed therein.

  In the cermet of the present invention, the denitrification during sintering is a first hard carbonitride that contains at least one of elements in Group 5a and 6a of the periodic table, at least one of Zr and Hf, and Ti. A second surface layer having an effect of forming a first surface layer including a phase, wherein the nitriding treatment at the time of temperature increase includes at least one second hard phase selected from Zr and Hf nitrides and carbonitrides. The formed first surface layer has an effect of improving chipping resistance, and the formed second surface layer has an effect of improving wear resistance and plastic deformation resistance. The composite surface layer composed of the first surface layer and the second surface layer has the effect of simultaneously improving both the wear resistance and chipping resistance of the entire cermet.

  The cermet having the composite surface layer of the present invention is less likely to cause chipping than the conventional cermet, and therefore has an effect that a cutting life of about 1.7 times can be achieved.

Using commercially available powders of TiC, TiN, Ti (C _0.5 N _0.5 ), ZrN, HfN, NbC, TaC, WC, Mo ₂ C, Co, Ni, Cr ₂ N with an average particle diameter of 1 to 2 μm The mixture composition shown in Table 1 was weighed, inserted into a stainless steel pot together with an acetone solvent and a cemented carbide ball, mixed and ground for 48 hours, and dried to obtain a mixed powder.

  These mixed powders are filled in a chip die with a breaker of SNMG120408 in accordance with ISO standards, a green compact is produced with a pressure of 200 MPa, and placed on a carbon plate coated with carbon black powder, and then a sintering furnace The cermet chips of the present invention products 1 to 8 and comparative products 1 to 7 were obtained. Details of the atmosphere in each of the applied temperature raising, nitriding treatment, sintering, and cooling steps are collectively shown in Table 2, and the condition number and the temperature and time during sintering are also shown in Table 1.

  After cutting each one of the obtained cermet chips, the flank cross section was ground and lapped with 1 μm diamond paste, and the structure of the hard phase was observed with an optical microscope and a scanning electron microscope. The average thickness of the first surface layer (the hard phase is composed only of solid carbonitride particles of composite carbonitride) and the second surface layer (the hard phase is one or more nitrides of Zr and Hf, carbonitride) The average thickness of the single particles of the product and the solid solution particles of the composite carbonitride was measured. Also, X-ray diffraction is performed while grinding and lapping the flank face of another chip from the surface to the inside, and the hard phase component inside 0.1 mm from the center and the surface of the first surface layer and the second surface layer. Identified. These results are shown in Table 3. In addition, when the first surface layer and the second surface layer are not present in the comparative product, the results measured in the interior of 5 μm from the surface and the interior of 20 μm from the surface are respectively shown in the columns of the first surface layer and the second surface layer Described.

注）＊ＳＳは（Ｔｉ，Ｚｒ/Ｈｆ，Ｎｂ/Ｔａ，Ｍｏ/Ｗ）（Ｃ，Ｎ）系の複合炭窒化物を意味する。

Note) * SS means (Ti, Zr / Hf, Nb / Ta, Mo / W) (C, N) based composite carbonitride.

  In addition, with respect to the sample in which the cross section on the flank side is observed, a tissue photograph of 0.1 mm inside is taken from the center and the surface of the first surface layer and the second surface layer using a scanning electron microscope, and an image processing apparatus In the hard phase excluding the binder phase, composite carbonitride solid solution particles (referred to as SS), at least one nitride of Zr and Hf, carbonitride single particles (referred to as ZHN), Ti carbide, charcoal The content volumes of cored structure particles (referred to as CRS) having nitride as the core and composite carbonitride as the surrounding structure, Ti nitride, carbonitride single particles (referred to as TN), and the like were determined. Here, in the case where the first surface layer and the second surface layer were not present in the comparative product, they were substituted at positions within 5 μm and 20 μm from the surface, respectively. The results are shown in Table 4.

  From the results of Tables 3 and 4, all the products of the present invention have a composite surface layer, but Comparative Product 1 with a small amount of ZrN added, Comparative Product 2 with a large amount of ZrN added, Comparative Products 3 and 4 with a small TiC content, In the comparative products 5 and 6 that are not nitrided and the comparative product 7 that is nitrided and sintered without the nitriding treatment, the first surface layer is formed, but the second surface layer having a different structure from the inside is not formed. I understand.

  Next, about the sample which observed the cross section of said flank side, the component inside 0.1 mm from the center part and surface of the 1st surface layer and the 2nd surface layer was analyzed with the scanning analysis electron microscope. The results are shown in Table 5.

  From the results of Table 5, it can be seen that the first surface layer and the second surface layer are formed in the product of the present invention.

  After grinding the upper and lower surfaces of the cermet chips of the present invention products 3, 4, 5, 7, 8 obtained in Example 1 and the comparative products 1, 3, 4, 6, 7 with a # 230 diamond grindstone, The cutting edge was subjected to a round honing process of 0.05 mm. Then, cut material: 4-grooved carbon steel S45C, cutting speed: 150 m / min, depth of cut: 2.0 mm, feed: 0.2 mm / rev. Time was measured until chipping occurred or the flank wear amount reached 0.20 mm. The results are shown in Table 6.

  Looking at the results in Table 6, the comparative product is prone to abrupt wear, chipping and chipping due to plastic deformation, whereas the product of the present invention progresses normal wear and minute chipping. It has become.

Claims (7)

In a cermet composed of at least one hard phase of carbides, nitrides and mutual solid solutions of the elements 4a, 5a and 6a of the periodic table, and a binder phase mainly composed of at least one of Co and Ni A first surface layer having an average thickness of 2 to 20 μm is formed from the baked skin surface of the cermet toward the inside, and a second surface having an average thickness of 5 to 50 μm from the interface between the first surface layer and the second surface layer to the inside. A surface layer is formed,
(1) The first surface layer is bonded to a first hard phase of a composite carbonitride containing one or more elements in the periodic table 5a and 6a group elements, one or more elements in Zr and Hf, and Ti. Consist of phases
(2) The second surface layer is composed of at least one second hard phase among the nitride of Zr, Hf, carbonitride, and their mutual solid solution, the first hard phase, and the binder phase.
(3) The inside of the cermet excluding the first surface layer and the second surface layer is composed of Ti carbide or carbonitride as a core and one or more elements in the periodic table 5a, 6a group elements and Zr, Hf Including a third hard phase having a core structure having a composite carbonitride containing at least one of Ti and Ti as a peripheral portion, a first hard phase, and a binder phase;
Cermet with composite surface layer.   The cermet having a composite surface layer according to claim 1, wherein the cermet comprises a hard phase: 75 to 95% by weight based on the whole cermet and a binder phase: 5 to 25% by weight based on the whole cermet.   The hard phase is composed of at least one of Zr, Hf nitrides, carbonitrides and their mutual solid solutions: 5 to 25% by weight with respect to the entire hard phase, and carbides of elements in Group 5a and 6a of the periodic table. At least one of nitride and carbonitride: 10 to 40% by weight based on the entire hard phase, and at least one of Ti carbide and carbonitride: 35 to 85% by weight based on the entire hard phase A cermet having a composite surface layer according to claim 1 or 2. The amount of nitrogen N _S1 included in the first surface layer (wt%), the amount of nitrogen contained in the second surface layer N _S2 (wt%), representing the amount of nitrogen contained within N _I (% by weight) The cermet having a composite surface layer according to claim 1, wherein N _S1 , N _S2 , and N _I satisfy N _S2 > N _I > N _S1 . The periodic table 6a group element amount contained in the first surface layer is 6a _S1 (wt%), the periodic table table group 6a group element amount contained in the second surface layer is 6a _S2 (wt%), and the periodic table contained therein. 6a _S1 , 6a _S2 , 6a _I satisfy 6a _S1 > 6a _I > 6a _S2 when the amount of group 6a element is expressed as 6a _I (weight%). Cermet with a composite surface layer. The content of at least one of Co and Ni contained in the first surface layer is BD _S1 (wt%), the content of at least one of Co and Ni contained in the second surface layer is BD _S2 (wt%), The BD _S1 , BD _S2 and BD _I satisfy BD _I > BD _S2 ≧ BD _S1 when the content of at least one of Co and Ni contained therein is expressed as BD _I (wt%). The cermet which has a composite surface layer of any one of -5.   In the method for producing cermet, (a) at least one of nitrides of Zr and Hf, carbonitrides and their mutual solid solution: 5 to 25% by weight based on the whole hard phase forming powder, and (b) period At least one of carbides, nitrides and carbonitrides of Group 5a and 6a elements: 10 to 40% by weight with respect to the entire hard phase forming powder, and (c) at least of Ti carbides and carbonitrides 1 type: Prepare hard phase forming powder consisting of 35 to 85% by weight with respect to the entire hard phase forming powder, and binder phase forming powder consisting of at least one of Co and Ni. Hard phase forming powder: mixture A step of mixing 75 to 95% by weight with respect to the whole and a binder phase forming powder: 5 to 25% by weight with respect to the whole mixture to obtain a mixture, and a pressure of 10 kPa or more at a temperature of 1100 to 1300 ° C. In nitrogen gas Step and the mixture and a step of sintering at below nitrogen gas pressure 5kPa at a temperature of from 1,400 to 1550 ° C., the manufacturing method of the cermet having a composite surface layer.