Patent Publication Number: US-7909905-B2

Title: TiCN-base cermet and cutting tool and method for manufacturing cut article using the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §120 to PCT Application No. PCT/JP2006/304714, filed on Mar. 10, 2006, entitled “TiCN BASE CERMET AND CUTTING TOOL AND METHOD FOR MANUFACTURING CUT ARTICLE USING THE SAME.” The contents of this application are incorporated herein by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a TiCN-base cermet having satisfactory toughness and hardness as, for example, a cutting tool material or a wear-resistant tool material and relates to a cutting tool made of the TiCN-base cermet. The present invention further relates to a method for manufacturing a cut article with this cutting tool. 
     BACKGROUND 
     Cemented carbides (WC-base sintered alloys) are known as alloys for cutting tool materials or wear-resistant tool materials. However, the cutting tools of the cemented carbides are easily worn at rake faces by cutting steel. In order to solve this problem, cermet alloys have been developed. For example, TiC-base cermets containing TiC as main components have been developed, however, these materials are insufficient in toughness, and therefore TiCN-base cermets further containing TiN are widely used. 
     It is known that modifying the hard particle in the TiCN-base cermets into a core-containing structure particle having a core and a shell can improve the hardness and the toughness of the TiCN-base cermets. The hard particle has most influence on the mechanical property of the TiCN-base cermets (see Japanese Unexamined Patent Application Publication No. 2-254131, and Japanese Unexamined Patent Application Publication No. 10-287946 etc.). The contents of these publications are incorporated herein by reference in their entirety. 
     Japanese Unexamined Patent Application Publication No. 3-170637 discloses a cermet which includes hard particles having cores and shells composed of carbonitrides of metals (hard metals) belonging to group IVa, Va, or VIa of the periodic table. The hard particles include plural kinds of core-containing structure particles which have cores and/or shells composed of plural kinds of the hard metals. The cermet can improve the defect resistance (toughness) without a decrease in wear resistance (cutting resistance). The contents of this publication are incorporated herein by reference in their entirety. 
     Japanese Unexamined Patent Application Publication No. 11-229068 discloses that sintering properties can be improved by dispersing superfine alloy particles composed of a binding metal made of Co and/or Ni in hard particles having a core-containing structure, and thereby even cermets having a small binding phase can be densified. The contents of this publication are incorporated herein by reference in their entirety. 
     However, hard particles having a core-containing structure, such as those disclosed in Japanese Unexamined Patent Application Publications No. 2-254131 and No. 10-287946, have limitation in improvement of mechanical properties and cutting performance. In particular, TiCN-base cermets whose thermal shock resistance and chipping resistance are equal to those of a WC-base sintered alloy provided with a hard coating film on the surface have been desired. 
     In the particles having a plurality of core-containing structures whose cores and shells have different compositions each other, as those disclosed in Japanese Unexamined Patent Application Publication No. 3-170637, since the hard particles consist of only hard metals such as carbonitride, the thermal conductivity of a cermet is low. Therefore, generated heat in a cutting edge due to cutting cannot be efficiently dissipated. As a result, disadvantageously, the temperature of the cutting edge increases and thermal shock resistance and chipping resistance decreases. 
     Furthermore, as in Japanese Unexamined Patent Application Publication No. 3-170637, dispersing superfine alloy particles made of a binding metal in hard particles improves the sintering properties of the cermet. However, a binding metal having a low hardness is present in the form of particles. Besides, the binding phase is originally in a low proportion and has a low binding force. Therefore, the strength of the sinter decreases and the binding metal particles may cause breakage or chipping. 
     SUMMARY 
     According to one aspect of the invention, a cermet comprises a binding phase made of a binding metal including Co and/or Ni. The binding phase is 5 to 30 mass %. The cermet also comprises a plurality of hard particles bound each other with the binding phase. A part of the hard particles comprises core-containing structure particles having cores and shells both including TiCN. The core-containing structure particles comprise first core-containing structure particles of which shells contain the binding metal and second core-containing structure particles of which cores and shells both contain the binding metal. 
     According to another aspect of the invention, a cutting tool comprises a rake face; a flank face; and a cutting edge comprising the cermet. The cutting edge is formed in a cross-ridge portion between the rake face and the flank face. 
     According to another aspect of the invention, a method for manufacturing a cut article with a cutting tool comprises preparing an article and a cutting tool which comprises the cermet. The method further comprises putting the cutting edge to the article to obtain the cut article. 
     According to another aspect of the invention, a cermet comprises a binding phase made of a binding metal including Co and/or Ni. The binding phase being 5 to 30 mass %. The cermet further comprises a plurality of hard particles bound each other with the binding phase. The hard particles comprise core-containing structure particles having cores and shells both including TiCN and the binding metal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1(   a ) is an enlarged image of a cross-sectional structure of a TiCN-base cermet according to an embodiment of the present invention, obtained using a transmission electron microscope (TEM), and  FIG. 1(   b ) is an enlarged image of a first core-containing structure particle of the cermet in  FIG. 1(   a ). 
         FIG. 2  is a schematic diagram illustrating a cutting tool according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     The present inventors have conducted intensive studies for solving the above-mentioned problems of the related arts and have found the fact that the following cermet can maintain a high hardness and a high toughness thereof, and can improve the thermal shock resistance and the chipping resistance thereof. The cermet comprises a binding metal phase composed of Co and/or Ni, and hard particles bound with the binding metal phase. The hard particles have the core-containing structure particles which have cores and shells, both of which include TiCN. The core-containing structure particles include first core-containing structure particles of which shells contain the binding metal and second core-containing structure particles of which cores and shells both contain the binding metal. 
     When the content ratio of the binding metal in the core of the second core-containing structure particles is from 0.5 mass % to 5 mass %, the chipping resistance of the cermet can be enhanced without the major deterioration of wear resistance even though the cermet does not comprises the first core-containing structure the wear resistance of cermet. 
     TiCN-Base Cermet 
     A TiCN-base cermet (hereinafter simply referred to as “cermet”) according to an embodiment of the present invention will now be described in detail with reference to the drawings.  FIG. 1(   a ) is an enlarged image of the cross-sectional structure of any cross-section of a cermet according to an embodiment of the present invention, obtained using a transmission electron microscope (TEM), and  FIG. 1(   b ) is an enlarged image of a first core-containing structure particle of the cermet in  FIG. 1(   a ). 
     As shown in  FIG. 1(   a ), the cermet  1  according to this embodiment comprises the binding phase  2  and hard particles  3  bound with the binding phase  2 . The binding phase  2  comprises a Co and/or Ni binding metal and is present in an amount of 5 to 30 mass % based on the total amount of the cermet  1 . When the content of the binding phase  2  is lower than 5 mass %, the toughness is decreased and thereby the chipping resistance is decreased. When the content of the binding phase  2  is higher than 30 mass %, the wear resistance and the plastic deformation resistance of the cermet  1  are decreased. 
     The observation of a cross-sectional structure by a microscope, as shown in  FIG. 1(   a ), shows that a part of the hard particles  3  includes core-containing structure particles  6  which have a structure composed of a core  4  and a shell  5  both comprising TiCN. 
     Since the hard particles  3  constituting the core-containing structure particles  6  have a grain-growth-inhibiting effect, the cermet  1  can have a fine and uniform structure. In addition, the excellent wettability of the hard particles  3  with the binding phase  2  also contributes to the enhancement of strength of the cermet  1 . 
     As shown in  FIGS. 1(   a ) and  1 ( b ), the core-containing structure particles  6  include first core-containing structure particles  6   a  of which shells  6   a  contain the binding metal (Co and/or Ni) and second core-containing structure particles  6   b  of which cores  4   b  and shells  5   b  both contain the binding metal. Core-containing structure particles  6  including these two types of core-containing structure particles  6   a  and  6   b  can enhance the thermal conductivity efficiency while maintaining high hardness and high toughness of the hard particles  3 . Therefore, locally generated heat can be quickly dissipated and, as a result, thermal shock resistance and chipping resistance of the cermet  1  are improved. 
     When the core-containing structure particles  6  do not include both such designated core-containing structure particles  6   a  and  6   b , the locally generated heat is hard to be not quickly dissipated, and also the toughness of the cermet  1  becomes insufficient or the hardness of the cermet  1  is reduced. Therefore, the thermal shock resistance, chipping resistance, and wear resistance of the cermet  1  cannot be sufficiently enhanced. Consequently, for example, a cutting tool made of such a cermet  1  has a short tool life. 
     When the content ratio of the bound metal in the core  4   b  of the second core-containing structure particles is from 0.5 mass % to 5 mass %, the chipping resistance of the cermet  1  can be enhanced without the major deterioration of wear resistance even though the cermet  1  does not comprises the first core-containing structure the wear resistance of cermet  1 . 
     The core-containing structure particles  6  include both the first core-containing structure particles  6   a  and the second core-containing structure particles  6   b . This means that the first core-containing structure particles  6   a  and the second core-containing structure particles  6   b , these two types of particles, are independently present (coexist) among the core-containing structure particles  6 . The presence of the core-containing structure particles  6   a  and  6   b  and their compositions can be measured by cross-sectional structure observation using a transmission electron microscope (TEM) and then by energy dispersive X-ray spectroscopy (EDS) analysis as described below, for example. 
     In particular, it is preferred that the first core-containing structure particle  6   a  comprises a core  4   a  including TiCN and a shell  5   a  including a complex carbonitride of Ti and at least one element selected from the group consisting of Ta, Nb, W, Zr, and Mo. The shell  5   a  also includes the binding metal. It is preferred that the second core-containing structure particle  6   b  comprises a core  4   b  including TiCN and the binding metal. The second core-containing structure particle  6   b  comprises a shell  5   b  including a complex carbonitride of Ti and at least one element selected from the group consisting of Ta, Nb, W, Zr, and Mo. When the core-containing structure particles  6   a  and  6   b  have such structures, the thermal shock resistance, the chipping resistance, and the wear resistance of the cermet  1  are further enhanced. 
     The proportion p 1 /(p 1 +p 2 ) where a presence ratio p 1  is the ratio of the first core-containing structure particles  6   a  to all the core-containing structure particles and a presence ratio p 2  is the ratio of the second core-containing structure particles  6   b  to all the core-containing structure particles is preferably 0.3 to 0.7. With such a proportion, both high hardness and high toughness of the cermet  1  can be maintained. 
     The average particle diameter of the hard particles  3  is preferably 1.5 μm or less. With such a particle diameter, the hardness of the cermet  1  can be increased. The lower limit of the average particle diameter is preferably 0.4 μm or more in view of effective prevention of a decrease in resistance to chipping caused by significant fineness of particles. The average particle diameter is a value obtained by analyzing the hard particles  3  using a Luzex image analyzer in observation of a cross-sectional structure of the cermet  1  using a microscope. 
     It is preferred that the cores  4   b  of the second core-containing structure particles  6   b  contain 94 to 99.5 mass % of Ti and 0.5 to 6 mass % in total of Co and/or Ni. With such cores, the thermal shock resistance of the cermet  1  can be enhanced while the high hardness of the cermet  1  is maintained. Each amount of Ti, Co, and Ni is an amount of each element which exists as a metal element. 
     Furthermore, it is preferred that the shells  6   a  and  6   b  of the first core-containing structure particles  6   a  and the second core-containing structure particles  6   b  each contain 40 to 80 mass % of Ti, 15 to 59 mass % in total of at least one element selected from the group consisting of Ta, Nb, W, Zr, and Mo, and 1 to 5 mass % in total of Co and/or Ni. With such shells, the cermet  1  can have high toughness and the thermal shock resistance, and the chipping resistance of the cermet  1  can be enhanced. Each amount of Ti, Ta, Nb, W, Zr, Mo, Co, and Ni is an amount of each element which exists as a metal element. 
     Similarly as above, compositions and composition ratios of the cores  4   a  and  4   b  and the shells  5   a  and  5   b  can be measured by cross-sectional structure observation using a transmission electron microscope (TEM) and then by energy dispersive X-ray spectroscopy (EDS) analysis. 
     In addition to the first core-containing structure particles  6   a  and the second core-containing structure particles  6   b , the cermet  1  may further include a non-core-containing structure particles to the extent that a cross-section observed through the microscope include 30 area % or less of non-core-containing structure particles based on the total area of the hard particles  3 . Furthermore, aggregation of the binding metal may be present in the core-containing structure particles  6 . 
     It is desirable that the carbon content of the cermet  1  be 6 to 9 mass %, particularly 6.5 to 7.5 mass %, in view of achieving satisfactory hardness and thermal shock resistance and favorable surface conditions. 
     Manufacturing Process 
     Next, a method for manufacturing the above-described cermet  1  will be described. First, powdery raw materials are prepared and mixed. Specifically, it is preferred that both a usual TiCN powder and a Co/Ni-doped TiCN powder, which is prepared by previously adding a binding metal of Co and/or Ni to the TiCN powder, be used. Then, a powder mixture is prepared by mixing these powders; a TiN powder; at least one powder of carbides, nitrides, and carbonitrides which contain one or more metal elements selected from the group consisting of W, Mo, Ta, V, and Nb; and a Co powder and/or Ni powder. 
     It is desirable that the usual TiCN powder have an average particle diameter (by microtrac analysis) of 2 μm or less, particularly 0.05 to 1.5 μm, and the Co/Ni-doped TiCN powder have an average particle diameter of 2 μm or less, particularly 0.05 to 1.5 μm, from the viewpoint that the above-described two types core-containing structures  6   a  and  6   b  can be prepared with high reproducibility. 
     Furthermore, it is desirable that the Co powder and/or Ni powder have an average particle diameter of 2 μm or less, particularly 0.05 to 1.5 μm, for enhancing sintering properties of the cermet  1 . The use of a solid solution powder containing Co and Ni at predetermined ratios as the binding-metal powdery raw material is further desirable in view of further enhancing the sintering properties. It is desirable that the average particle diameters of other powdery materials be 0.05 to 3 μm. 
     The average particle diameter of each of the above-mentioned powder and powdery materials is measured by a micro-track method. 
     After addition of a binder to this powder mixture, the powder mixture is formed into a predetermined shape by a known process such as press molding, extrusion molding, or injection molding and is then fired. The preferable conditions for the firing are, for example, the following (a) to (d): the temperature is (a) increased from a first firing temperature to 1300° C. at a heating rate of 0.1 to 3° C./min; then (b) from 1300° C. to a second firing temperature of 1400 to 1600° C. at a heating rate of 5 to 15° C./min under an atmosphere of a nitrogen partial pressure of 0 to 135 Pa; (c) maintained, and (d) then decreased. 
     Cutting Tool 
     The above-described cermet  1  according to this embodiment exhibits excellent thermal shock resistance and chipping resistance. The cermet  1  is applicable to various tools such as cutting tools, mining tools, and blades. In particular, the above-described excellent performance of the cermet can be exhibited in cutting tools. 
     The cutting tool is preferably, for example, as illustrated in  FIG. 2 , a cutting tool  20  of the cermet  1  and having a cutting edge  23  formed at a cross-ridge portion between a rake face  21  and a flank face  22  and is used for cutting an article by applying the cutting edge  23  to the article. Such a cutting tool  20  can have a long tool life by applying the cutting edge  23  of the cutting tool  20  to a metal such as iron and aluminum or a heat-resistant alloy. Furthermore, the cutting tool can also exhibit excellent cutting properties in cutting an article which is difficult to be cut, such as highly hardened steel. 
     The cermet  1  can also have excellent mechanical confidence in applications other than the cutting tool, for example, in wear-resistant members such as a mold, mill roll, die, and guide; a blade; and bearings. 
     The present invention will now be described in detail with reference to Examples, but is not limited to the following Examples. 
     EXAMPLES 
     TiCN powder, TiCN powder doped with 10 mass % of Co, TiN powder, ZrC powder, VC powder, TaC powder, NbC powder, WC powder, MoC powder, Ni powder, Co powder, and solid solution powder of Ni and Co having average particle diameters shown in Tables 1 and 2 were prepared and these powders were blended so as to have compositions shown in Tables 1 and 2. 
     Then, each of the blends was wet mixed in isopropyl alcohol (IPA) using a stainless steel ball mill and a cemented carbide ball, and 3 mass % of paraffin was added thereto. The resulting mixture was further mixed. Then, the powder mixture was press-formed into a throw-away tip shape of ISO CNMG120408 at 200 MPa and was then fired under conditions shown in Tables 1 and 2 to obtain a sinter (Sample Nos. 1 to 10 in Table 1, Sample Nos. 11 and 12 in Table 2). 
     In sample No. 5 in Table 1, sources of Co and Ni were a solid solution powder containing Ni and Co (Ni: 5 mass %, Co: 6.5 mass %) and a Ni powder (5 mass 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                 Composition (mass %), numerals in parentheses denote ratios of solid solution 
                   
               
               
                   
                 components (average particle diameter (μm) of powdery raw material) 
                 Firing conditions 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 TiCN + 
                   
                   
                   
                   
                   
                   
                   
                   
                 First firing 
                   
                 Second firing 
                   
               
               
                 Sample 
                   
                 10 mass % 
                   
                   
                   
                   
                   
                   
                   
                   
                 temperature 
                 Heating 
                 temperature 
                 Heating 
               
               
                 No. 
                 TiCN 
                 of Co 
                 TiN 
                 TaC 
                 NbC 
                 WC 
                 ZrC 
                 VC 
                 Ni 
                 Co 
                 (° C.) 
                 rate I 1)   
                 (° C.) 
                 rate II 2)   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 22.5 
                 25 
                 13 
                 — 
                 — 
                 20 
                 3 
                 — 
                 7(7) 
                 9.5(9.5) 
                 1000 
                 0.3 
                 1500 
                 10 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                   
                   
                 (1.0) 
                 (2.5) 
                   
                 (1.0) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 2 
                 11 
                 10 
                 35 
                 5 
                 10 
                 7 
                 3 
                 — 
                 10(10) 
                 9(9) 
                 900 
                 0.3 
                 1450 
                 13 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 (1.5) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                 (2.5) 
                   
                 (1.0) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 3 
                 11 
                 10 
                 30 
                 9 
                 10 
                 13 
                 — 
                 — 
                 3(3) 
                 14(14) 
                 1000 
                 0.5 
                 1550 
                 8 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                   
                   
                 (1.0) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 4 
                 22 
                 20 
                 20 
                 — 
                 — 
                 20 
                 2 
                 — 
                 8(8) 
                 8(8) 
                 1100 
                 1 
                 1570 
                 5 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 (0.7) 
                 (0.7) 
                 (2.0) 
                   
                   
                 (1.0) 
                 (2.5) 
                   
                 (1.0) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 5 
                 16.5 
                 15 
                 30 
                 — 
                 20 
                 — 
                 — 
                 2 
                 10(5)  
                 6.5(6.5) 
                 850 
                 2 
                 1525 
                 8 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                   
                 (2.0) 
                   
                   
                 (1.0) 
                 (1.5(Ni)) 
                   
                   
                   
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 (1.0(Co/Ni)) 
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 6 
                 17 
                 20 
                 20 
                 — 
                 5 
                 20 
                 — 
                 — 
                 10 
                 8 
                 950 
                 2.5 
                 1530 
                 12 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                   
                 (2.0) 
                 (1.0) 
                   
                   
                 (1.5) 
                 (1.0) 
                   
                   
                   
                   
               
               
                 7 
                 26.5 
                 15 
                 12 
                 10 
                 10 
                 10 
                 — 
                 — 
                 8 
                 8.5 
                 1050 
                 3 
                 1600 
                 7 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                   
                   
                 (1.5) 
                 (1.0) 
                   
                   
                   
                   
               
               
                 * 8     
                 30 
                 — 
                 30 
                 5 
                 10 
                 10 
                 — 
                 2 
                 6 
                 7 
                 1200 
                 0.2 
                 1500 
                 6 
               
               
                   
                 (0.7) 
                   
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                   
                 (1.0) 
                 (1.5) 
                 (1.0) 
                   
                   
                   
                   
               
               
                 * 9     
                 15 
                 10 
                 30 
                 10 
                 5 
                 15 
                 3 
                 — 
                 6 
                 6 
                 — 
                 — 
                 1600 
                 3 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                 (2.5) 
                   
                 (1.5) 
                 (1.0) 
                   
                   
                   
                   
               
               
                 * 10     
                 10 
                 10 
                 25 
                 20 
                 5 
                 5 
                 3 
                 5 
                 7 
                 10 
                 1000 
                 5 
                 1450 
                 16 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                 (2.5) 
                 (1.0) 
                 (1.5) 
                 (1.0) 
               
               
                   
               
               
                 The mark “*” means the sample which is outside the range of the present invention. 
               
               
                   1) Heating rate I: heating rate (° C./min) in the range of from the first firing temperature to 1300° C. 
               
               
                   2) Heating rate II: heating rate (° C./min) in the range of from 1300° C. to the second firing temperature 
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
                 Composition (mass %), numerals in parentheses denote ratios of solid solution 
                   
               
               
                   
                 components (average particle diameter (μm) of powdery raw material) 
                 Firing conditions 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 TiCN + 
                   
                   
                   
                   
                   
                   
                   
                   
                 First firing 
                   
                 Second firing 
                   
               
               
                 Sample 
                   
                 10 mass % of 
                   
                   
                   
                   
                   
                   
                   
                   
                 temperature 
                 Heating 
                 temperature 
                 Heating 
               
               
                 No. 
                 TiCN 
                 Co 
                 TiN 
                 TaC 
                 NbC 
                 WC 
                 ZrC 
                 MoC 
                 Ni 
                 Co 
                 (° C.) 
                 rate I 1)   
                 (° C.) 
                 rate II 2)   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 11 
                 32 
                 18 
                 10 
                 — 
                 5 
                 20 
                   
                 2 
                 5 
                 10 
                 1050 
                 1 
                 1575 
                 3 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                   
                 (2.0) 
                 (1.0) 
                   
                 (2.5) 
                 (1.5) 
                 (1.0) 
                   
                   
                   
                   
               
               
                 12 
                 30 
                 10 
                 10 
                 5 
                 10 
                 7 
                 3 
                 — 
                 5 
                 10 
                 1000 
                 5 
                 1450 
                 7 
               
               
                   
                 (0.7) 
                 (1.0) 
                 (2.0) 
                 (2.0) 
                 (2.0) 
                 (1.0) 
                 (2.5) 
                   
                 (1.5) 
                 (1.0) 
               
               
                   
               
               
                   1) Heating rate I: heating rate (° C./min) in the range of from the first firing temperature to 1300° C. 
               
               
                   2) Heating rate II: heating rate (° C./min) in the range of from 1300° C. to the second firing temperature 
               
            
           
         
       
     
     The surface of the resulting sinter was machined with a diamond whetstone, and cutting properties were evaluated under conditions below. The core-containing structure particles of each sample were observed using a transmission electron microscope (TEM) and using analysis by energy dispersive X-ray spectroscopy (EDS) for confirming the presence of the first core-containing structure particles and the second core-containing structure particles, for confirming composition ratios of the cores and the shells. The results are shown in Table 3. 
     Furthermore, cutting was performed using the resulting throw-away tips under the following conditions, and performances as cutting tools were evaluated. 
     (Cutting Condition)
         Cutting speed: 300 m/min   Feed: 0.25 to 0.40 mm/rev (+0.05 mm/rev)   Depth of cut: 2.0 mm   Article: SCM435, 5 mm×4 grooves   Cutting time: 60 sec (cutting time at each feed)   Cutting conditions: wet (emulsion)       

     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
                 Composition (mass %) of hard particle 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 First core-containing structure particle 
                 Second core-containing structure particle 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Shell composition 
                   
                 Shell composition 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Metal element 
                 Metal element 
                 Cutting 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sample 
                   
                 constituting complex 
                 Core 
                   
                 constituting complex 
                 life 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 No. 
                 Existence 
                 Ti 
                 Co + Ni 
                 carbonitride 
                 Existence 
                 Ti 
                 Co + Ni 
                 Ti 
                 Co + Ni 
                 carbonitride 
                 (sec) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 Presence 
                 60 
                 2 
                 W35, Zr3 
                 Presence 
                 98.5 
                 1.5 
                 65 
                 2 
                 W31, Zr2 
                 295 
               
               
                 2 
                 Presence 
                 46.5 
                 1.5 
                 Nb20, W15, Ta10, Zr7 
                 Presence 
                 97.4 
                 2.6 
                 47 
                 2 
                 Nb20, W15, Ta12, Zr4 
                 216 
               
               
                 3 
                 Presence 
                 51 
                 1 
                 W20, Nb15, Ta13 
                 Presence 
                 98.2 
                 1.8 
                 55 
                 1 
                 W17, Nb15, Ta12 
                 223 
               
               
                 4 
                 Presence 
                 63 
                 2 
                 W32, Zr3 
                 Presence 
                 98.3 
                 1.7 
                 65.8 
                 2.2 
                 W30, Zr2 
                 292 
               
               
                 5 
                 Presence 
                 65.8 
                 1.2 
                 Nb30, V3 
                 Presence 
                 97.5 
                 2.5 
                 63.1 
                 1.4 
                 Nb32, V3.5 
                 215 
               
               
                 6 
                 Presence 
                 69.9 
                 2.1 
                 W20, Nb8 
                 Presence 
                 97.9 
                 2.1 
                 66 
                 2.3 
                 W26.7, Nb5 
                 210 
               
               
                 7 
                 Presence 
                 47.2 
                 1.8 
                 W15, Nb18, Ta18 
                 Presence 
                 98.2 
                 1.8 
                 49.5 
                 1.5 
                 W16, Nb22, Ta11 
                 145 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 * 8     
                 Presence 
                 46 
                 1 
                 W18, Nb22, Ta10, V3 
                 Absence 
                 — 
                 53 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 * 9     
                 Absence 
                 — 
                 Presence 
                 94.1 
                 5.9 
                 40.2 
                 1.8 
                 W30, Nb15, Ta13 
                 44 
               
               
                 * 10     
                 Absence 
                 — 
                 Presence 
                 93.8 
                 6.2 
                 51.5 
                 1.5 
                 Ta20, Nb10, W5, Zr5, V7 
                 42 
               
               
                 * 11     
                 Absence 
                 — 
                 Presence 
                 97.9 
                 2.1 
                 65 
                 2.5 
                 W28, Nb2.5, Mo2 
                 120 
               
               
                 * 12     
                 Absence 
                 — 
                 Presence 
                 85.2 
                 4.8 
                 40.3 
                 1.8 
                 W35, Nb21, Ta1.4 
                 110 
               
               
                   
               
               
                 The mark “*” means that the sample is outside the range of the present invention. 
               
            
           
         
       
     
     As obvious from the results shown in Table 3, samples Nos. 1 to 7, which were fired under prescribed conditions and were confirmed to have two types of core-containing structure particles, i.e., first core-containing structure particles and second core-containing structure particles, as the hard particles, had cutting lives longer than those of comparative samples Nos. 8 to 10. 
     In addition, the machined faces of cut articles (SCM435) machined with throw-away tips of samples Nos. 1 to 7 were glossy, and stable cutting machining was achieved. On the other hand, the machined faces of cut articles machined with throw-away tips of samples Nos. 8 to 10 were clouded and not glossy. 
     Furthermore, samples Nos. 11 and 12 had cutting lives longer than those of comparative samples Nos. 8 to 10.