KR0180522B1 - Nitrogen containing sintered hard alloy - Google Patents

Abstract

Nitrogen-containing hard alloys contain at least 75% by weight and at most 95% by weight of a hard phase containing Ti, a Group 6A metal and WC in a predetermined composition, and contain at least 5% by weight of 25% by weight containing Ni, Co and inevitable impurities. It contains up to 5% by weight or less, Ti is contained in an amount of 5% or more and 60% by weight in terms of carbide, etc., and 30% or more and 70% by weight or less in terms of carbides of the Periodic Table 6A metal is contained. Carbon + nitrogen) has an atomic ratio of 0.2 or more and less than 0.5, and a soft layer containing a binding phase metal and WC is present on the outermost surface, and contains WC in a thickness of 3 µm or more and 30 µm or less directly under the soft layer. There is a layer with little hard phase present. According to this composition, it is possible to provide a nitrogen-containing sintered hard alloy which can be used as a cutting tool with high reliability without surface coating even when processing under severe thermal shock conditions.

Description

Nitrogen containing sintered hard alloy

FIG. 1 is a micrograph (SEM image) of an alloy structure showing that the exudation layer is divided into three layers, and the outermost layer and the lowermost layer have a bonding layer of Co and Ni, and the middle layer has a WC layer.

2 and 3 are micrographs (EDX analysis) showing the distribution of Co element and Ni element in the same structure, respectively.

TECHNICAL FIELD The present invention relates to a nitrogen-containing sintered hard alloy, and more particularly, to a nitrogen-containing sintered hard alloy for the purpose of improving heat shock resistance, abrasion resistance, and strength as a material for a cutting tool.

Nitrogen-containing sintered hard alloys having a hard phase made of carbonitride or the like mainly composed of Ti and bonded to a metal containing Ni and Co have already been put into practical use as cutting tools. Since the nitrogen-containing sintered hard alloy has a remarkable atomization of the hard phase compared with the conventional sintered hard alloy containing no nitrogen, and as a result, the high temperature creep resistance has been significantly improved, and thus, the cutting tool in parallel with the so-called cemented carbide containing WC as a main component It is widely used as.

However, in such nitrogen-containing sintered hard alloys, the thermal conductivity of Ti, which is the main component of (i) carbonitride, is significantly smaller than that of WC, which is the main component of the cemented carbide, and therefore the thermal conductivity of such nitrogen-containing sintered hard alloys is that of the cemented carbide. The thermal expansion coefficient of the nitrogen-containing sintered hard alloy is about 1.3 times the thermal expansion coefficient of the cemented carbide, since it is about 1/2 of the figure, and (ii) the thermal expansion coefficient also depends on the characteristic value of the main component, similarly to the thermal conductivity. Therefore, the resistance to thermal shock is lowered. For this reason, for example, the coated cemented carbide is particularly suitable for cutting under conditions in which thermal shocks are severe, such as milling, cutting by a lathe of a lumber, or wet cutting where the groove fluctuates greatly. Compared with the above, there is a problem that the reliability of the nitrogen-containing sintered hard alloy is lowered.

In order to solve the conventional problem of such a nitrogen-containing sintered hard alloy, various improvements shown below have been attempted. For example, Japanese Laid-Open Patent Publication No. Hei 2-15139 contains 50% by weight or more of Ti in terms of nitride and the like and converts 6A group (Group VIB in the CAS version) elements such as W into carbides. It is suggested to control the sintering atmosphere by containing less than 40% by weight and having a nitrogen content of 0.4 to 0.6 with an atomic ratio of N / (C + N) to improve the surface roughness and to form a modified portion having high toughness and hardness at the surface layer. It is. Japanese Unexamined Patent Application Publication No. Hei 5-9646 controls the cooling process after sintering to control the cooling process after sintering containing Ti as a main component and containing less than 40% by weight in total in terms of carbides of W, Mo and Cr. A cermet is described in which a reduced area is formed on the surface, whereby compressive stress is collected on the surface.

However, in any cermet disclosed in the above publication, wear resistance and toughness were improved, but defect resistance was insufficient as compared with the coated cemented carbide. In addition, the thermal shock resistance is inferior, and in particular, sudden defects due to the development of cracks due to the occurrence of thermal cracking or both thermal shock and mechanical impact are likely to occur, and sufficient reliability is not obtained. That is, in the prior art, although the manufacturing cost is reduced by omitting the coating process, performance can only be achieved to a degree that is suitable. This indicates that there is a natural limit to the purpose of improving the strength against defects in the so-called cermet on the premise of containing a certain amount of Ti.

Accordingly, the present inventors have analyzed the cutting phenomenon such as the temperature distribution in various cuttings and studied the arrangement of the material components in the tool in detail, and found the following facts.

During cutting, the cutting portion is partly placed in a high temperature environment, such as a portion of the cutting blade surface in contact with the workpiece or a portion where the debris of the inclined surface is scratched. Comparing the cermet and the cemented carbide, as mentioned above, since the cermet has half the thermal conductivity of the cemented carbide, it is difficult for the heat generated from the surface to diffuse into the interior so that the surface is hot even though the surface is hot. Occurs rapidly. In such a state, there is a problem that once a crack occurs, the defect is remarkably easily lost. In addition, if the hot cermet is quenched with water soluble coolant or cut idle to cool, only its extreme surface portion is cooled. Comparing the cermet and the cemented carbide, as mentioned above, since the cermet has a coefficient of thermal expansion of about 1.3 times that of the cemented carbide, tensile stress occurs in the surface layer portion, and thermal cracking is likely to occur very much. In the thermal shock resistance of any characteristic, the cermet side is more disadvantageous than the cemented carbide.

In addition, when viewed at the same particle size and the same amount of bonded phase, the cermet has a 30 to 50% lower fracture toughness value than the cemented carbide, so that the crack growth resistance inside the alloy is also lowered.

That is, in the nitrogen-containing sintered hard alloy, there is a limit to improving the thermal conductivity, lowering the coefficient of thermal expansion and improving the crack propagation resistance in a state in which a good cutting surface is contained and a large amount of advantageously Ti is contained. there is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nitrogen-containing sintered hard alloy which can be used as a cutting tool with high reliability even without a surface coating, even in a processing region under severe thermal shock, which has conventionally been used only as an expensive coated cemented carbide. It is.

Hereinafter, the first and second aspects of the present invention will be described.

The nitrogen-containing sintered hard alloy of the present invention aims to improve the resistance to crack growth if a large amount of WC is present inside the structure compared to conventional nitrogen-containing sintered hard alloys. When a large amount of WC is blended, in conventional nitrogen-containing sintered hard alloys, WC particles appear on the surface of the alloy to form a so-called P-type tool material, which reduces the properties of the cutting surface. For this reason, the abrasive wear resistance is also significantly inferior to the so-called cermet or coated cemented carbide.

However, when sintering is carried out in a specific high nitrogen atmosphere, it loses the soft layer present on the outermost surface of the tool, ie the surface portion from the bottom of the so-called extruded layer to a certain depth, which determines the properties of the cutting surface. It turned out to be possible. Thereby, the abrasion resistance and the crater wear resistance can be greatly improved, and in addition, if cooling is performed in a decarbonized atmosphere such as vacuum, the amount of bonding phase near the surface layer decreases and at the same time the hard phase A large amount of solid solution of Group 6A metal such as W is contained in the particles. In addition, when the alloy surface is hardened due to the effect of compressive stress on the surface portion due to the difference in coefficient of thermal expansion due to the difference in the coefficients of bonding phase, the toughness can be further improved. As a result, the wear resistance and the thermal shock resistance are remarkably increased. I can improve it.

Therefore, in the first aspect, the nitrogen-containing sintered hard alloy of the present invention includes (Ti · W _x M _y ) (C _u N _1-u ) (wherein M is at least one of Group 6A of the periodic table excluding W). And 0 <x <1, 0 ≦ y ≦ 0.9, 0 ≦ u ≦ 0.9) and a WC-containing hard phase containing 75 wt% or more and 95 wt% or less and containing Ni, Co and unavoidable impurities 5 wt% or more and 25 wt% or less of the combined phase to be contained, and 5 wt% or more and 60 wt% or less of Ti in terms of carbides, nitrides or carbonitrides, and 30 wt% or more in terms of carbides of Group 6A metals of the periodic table. It contains 70 wt% or less, and has a soft nitrogen / (carbon + nitrogen) in an atomic ratio of 0.2 or more and less than 0.5, and a soft layer containing a binding phase metal and WC is present on the outermost surface. It is characterized by having a layer with hardly any hard phase containing WC at a thickness of not less than 30 µm.

According to such a nitrogen-containing sintered hard alloy, first, the content of the hard phase is 75% by weight or more and 95% by weight or less. This is because when the hard phase is less than 75% by weight, the wear resistance and plastic resistance deformation are significantly lowered, and when the hard phase exceeds 95% by weight, the strength and toughness are insufficient. The content of Ti in terms of carbide or the like is 5% by weight or more and 60% by weight or less because the wear resistance does not reach a desired level at less than 5% by weight, and when the content is more than 60% by weight, the toughness deteriorates. It is preferable that content of such Ti is 5 weight% or more and 50 weight% or less, and it is especially preferable that they are 20 weight% or more and 50 weight% or less.

When the Group 6A metal in the periodic table is converted to carbide at 30% by weight to 70% by weight, desired toughness is not obtained at less than 30% by weight, and when it exceeds 70% by weight, a large amount of WC particles remain on the surface and wear resistance This is because this becomes insufficient and is not preferable. It is preferable that it is 40 weight% or more and 70 weight% or less, and, as for content which converted the group 6A metal of the periodic table into carbide, it is especially preferable that they are 40 weight% or more and 60 weight% or less.

When the atomic ratio of hard nitrogen / (carbon + nitrogen) is 0.2 or more and less than 0.5, when the atomic ratio is less than 0.2, both the toughness and the wear resistance do not reach a desired level, but when the ratio exceeds 0.5, the sintering property is lowered and the toughness deteriorates. Because it becomes. It is preferable that atomic ratio is 0.2 or more and less than 0.4.

In addition, the thickness of the layer containing hardly any WC-containing phase, specifically, 1 vol% or less, is set to 3 µm or more and 30 µm or less directly below the soft layer composed of the bonding phase metal and WC on the outermost surface. It is because the desired abrasion resistance and crater wear resistance cannot be obtained at less than 3 µm, and if it exceeds 30 µm, the effect of promoting crack growth resistance is not exerted, and as a result, the toughness is lowered.

In the preferred embodiment, the nitrogen-containing sintered hard alloy of the present invention contains the WC toward the inside from the layer in which the hard phase containing WC is hardly present in the composition to a maximum depth of 1 mm from the outermost surface. It is preferable that the amount of hard phase present gradually increases.

According to this structure, the amount of the hard phase containing WC gradually increases from the layer having the WC containing the hard phase containing 1 vol% or less to the maximum depth of 1 mm from the outermost surface, thereby increasing the amount of the hard phase containing the WC. Abrupt changes in the WC-containing distribution at the boundary with regions that do not exist are prevented, and generation of residual stresses at the boundary is alleviated.

In the above composition, the nitrogen-containing sintered hard alloy of the present invention preferably has a volume of WC-containing hard phase present in an amount of 5 vol% or more and less than 50 vol% within a depth of 1 mm or more from the outermost surface.

This is because the desired toughness-improving effect is not obtained at less than 5% by volume, and at least 50% by volume, the toughness to thermal shock of the surface portion and the plastic resistance deformation of the alloy are lowered.

In the second aspect, the nitrogen-sintered hard alloy of the present invention includes (Ti.W _x M _y ) (CuN _1-u ), except that M is a group of groups 4A, 5A, and 6A of the periodic table excluding Ti and W (CAS the version corresponds to Group IVB, Group VB, and Group VIB, respectively) and at least one of the metals, 0 <x <1, 0 <y <0.9, 0 ≦ u ≦ 0.9] and WC. It contains 75 wt% or more and 95 wt% or less, and contains 5 wt% or more and 25 wt% or less of a combined phase containing Ni, Co and unavoidable impurities, and 5 wt% of Ti in terms of carbide, nitride or carbonitride. 60% by weight or less, Periodic Table 6A metal in terms of carbide, 30% by weight or more, 70% by weight or less, total content of Ta and Nb in terms of carbide, nitride or carbonitride, 2% by weight or more and 15% by weight or less, V , The total content of Zr and Hf in terms of carbides, nitrides or carbonitrides up to 5% by weight, while hard nitrogen / (carbon + nitrogen) A layer having a ratio of 0.2 or more and less than 0.5, and a soft layer containing a binding phase metal and WC on the outermost surface, and hardly containing a hard phase containing WC in a thickness of 3 µm or more and 30 µm or less under the soft layer. It is characterized by having a.

Thus, in addition to the Group 6A metal of the periodic table excluding W, it contains the Group 4A metal and / or the Group 5A metal of the periodic table excluding Ti, and the total content of Ta and Nb is converted to carbide, nitride, or carbonitride by 15% by weight or more. It is equal to or less than the weight% and contains the total content of V, Zr and Hf in terms of carbides, nitrides or carbonitrides in an amount of 5% by weight or less, which has the same effect as the composition of the first aspect. If the total content in terms of less than 2% by weight, the crater wear resistance does not improve, and if it exceeds 15% by weight, the fracture resistance is lowered. It is preferable to contain V, Zr, and Hf in order to improve the strength and hardness at high temperature, but when the total content in terms of carbide and the like exceeds 5% by weight, the sintering property is lowered, and as a result, the fracture resistance is also lowered. .

In addition, the nitrogen-containing sintered hard alloy of the present invention has the amount of the hard phase containing WC inward from the layer where the hard phase containing WC hardly exists in the composition to the maximum depth of 1 mm from the outermost surface. It is desirable to increase gradually.

Furthermore, in the nitrogen-containing sintered hard alloy of the present invention, it is preferable that the amount of the hard phase containing WC in the composition is not less than 5 vol% and less than 50 vol% within 1 mm or more in depth from the outermost surface.

Next, a third aspect of the present invention will be described.

The occurrence of thermal cracking is caused by the temperature difference between the surface and the interior of the alloy. Means to be considered to prevent the occurrence of thermal cracking include improving the thermal conductivity of the nitrogen-containing sintered hard alloy itself, but there is a natural limit to the thermal conductivity improvement of the nitrogen-containing sintered hard alloy. However, by placing a WC-rich (cobalt-based metal-bonded phase) layer having a high thermal conductivity on the surface of the nitrogen-containing sintered hard alloy, the heat generated during cutting is conducted to the entire alloy to dissipate heat ( It is clear from the research that the effect of the fin) effect.

Therefore, in the third aspect of the present invention, the nitrogen-containing sintered hard alloy is made on the basis of the results of the above research, and it contains essentially WC and at least one transition metal selected from Groups 4A, 5A and 6A of the periodic table. It includes a hard phase containing carbide, nitride, carbonitride or complex carbonitride thereof, and a combined phase containing Ni, Co and inevitable impurities, and has the following structure and composition.

An exudation layer 1 for synthesizing WC and a metal-bonded phase composed mainly of Ni and Co exists in the alloy surface portion (see FIGS. 1 to 3), and the exudation layer 1 has three layers in the inner direction. The outermost layer is composed of a metal-bonded phase whose WC is 0 vol% or more and 30 vol% or less (preferably 0 to 5 vol%) and the balance is mainly composed of Co and Ni, and the intermediate layer is 50 vol WC. % Or more and 100% or less (preferably 80 to 100% by volume), and the balance is composed of a metal bonding phase containing Co and Ni as a main component, and the lowest layer has a WC of 0% to 30% by volume (preferably 0). To 5% by volume), and the balance is composed of a metal bonding phase containing Co and Ni as main components.

The thickness of the outermost layer and the thickness of the lowermost layer are each composed of 0.1 µm or more and 10 µm or less (preferably 0.1 µm to 0.5 µm), and the thickness of the intermediate layer is 0.5 µm or more and 10 µm or less (preferably 0.5 µm to 5 µm). to be.

According to the nitrogen-containing sintered hard alloy having such a structure, the thermal shock resistance is remarkably improved. In other words, the outermost layer and the lowermost layer are substantially enriched with a metal-bonded phase mainly composed of Ni and Co, but these layers are inevitable in the manufacturing process, and if the thickness is within the above range, no performance problem occurs.

In the numerical limitation of the above structure, the WC of the intermediate layer is 50 vol% or more and 100 vol% or less, if the WC is 50 vol% or less (the remainder is a metal-bonded phase composed mainly of Co and Ni), the desired thermal conductivity is not obtained. This is because it cannot play a role as a heat dissipating layer. The thickness of the intermediate layer is 0.5 µm or more and 10 µm or less because the desired thermal conductivity is not obtained when the thickness is less than 0.5 µm, and when the thickness is larger than 10 µm, wear resistance deteriorates remarkably.

The outermost layer and the lowermost layer are layers which are inevitably formed in order to obtain the intermediate layer, which is the most important layer, each of which requires at least 0.1 μm in thickness, but when the thickness exceeds 10 μm, the main component of the workpiece and iron are welded during cutting, Defects may occur. If the thickness is 10 μm or less, the results of the study show that there is no influence on cutting performance.

In the preferred embodiment, the nitrogen-containing sintered hard alloy of the present invention has the metal-bonded phase under the extruded layer 1 containing WC and the metal-bonded phase containing Ni and Co as main components in the alloy surface portion. It does not contain or contains the area which contains only 2 volume% or less, and the thickness of this area | region is 2 micrometers or more and 100 micrometers or less (preferably 2 micrometers) from the bottom of the exudation layer 1 in an inner direction. To 50 µm). According to such a structure, the said area | region just under the exudation layer 1 becomes very high hardness, and can be compatible with abrasion resistance and thermal shock resistance.

In the above structure, 2 vol% or less of the metal-bonded phase containing Co and Ni as a main component is contained in the alloy surface portion because a significant improvement in wear resistance is not recognized when the metal-bonded phase is present in a higher ratio. In addition, when the thickness of this area | region just under the exudation layer 1 shall be 2 micrometers or more and 100 micrometers or less, if the thickness of this area | region is less than 2 micrometers, the improvement of abrasion resistance will not be recognized and if it exceeds 100 micrometers, This is because it becomes too hard to cause brittleness and deterioration of fracture resistance.

In another preferred embodiment of the nitrogen-containing sintered hard alloy of the present invention having the above structure, a region containing no WC or only 2% by volume or less even under the exudation layer 1 contains an internal direction of the alloy. It has a thickness of 1 micrometer or more and 500 micrometers or less (preferably 20 micrometers-100 micrometers). Further, under these conditions, the volume% of WC gradually increases from just below the region just below the exudation layer 1 to the inside, and within 1 mm from the bottom of the exudation layer 1 (preferably 0.3). To a depth of 0.7 mm), the WC volume% is preferably the average WC volume% of the entire alloy. According to this structure, the presence of WC increases the Young's modulus of the entire alloy, and the mechanical strength is extremely high. In addition, it is possible to make both the thermal shock resistance and the fracture resistance by providing the WC only inside the alloy surface portion without the presence of WC.

In the above structure, the thickness in the inner direction of the region immediately below the exudation layer 1 that does not contain WC or contains only 2% by volume or less is 1 µm or more and 500 µm or less. It is because when the hardness is less than 1 µm, the wear resistance is affected by the decrease in hardness due to WC, and when the thickness exceeds 500 µm, the toughening effect of toughening of the alloy itself by WC is not obtained.

In addition, the structure of the alloy of the present invention mentioned above can be obtained by operating the sintering atmosphere and the cooling rate at a sintering temperature of 1350 ° C to 1700 ° C in the prescribed composition. The three layer thicknesses in the exudation layer 1 can be adjusted by controlling the sintering atmosphere and the cooling rate.

In addition, about the volume% of WC, the following measuring methods are used. The cross section of the cemented carbide of WC-Co, known as WC volume%, is rubbed and a SEM photograph of 4800 times is taken. The area occupied by the WC in the photograph is calculated using an image diffraction apparatus, and a calibration curve is drawn between the WC volume% and the occupied area of the WC using the image diffraction apparatus. For the alloy of the present invention, the site to be observed is subjected to cross-sectional rubbing, and the occupied area of the WC is calculated from a 4800-fold SEM photograph using an image diffraction apparatus, and the volume% of the WC is obtained from the calibration curve.

Hereinafter, specific examples of the present invention will be described.

Example 1

Powder with average particle diameter of 2 µm and outer part of core structure appearing white on reflecting electron microscope and black part of core (Ti _0.85 Ta _0.04 Nb _0.04 Wo _0.07 ) (C _0.56 No _0.44 ) Powder, average particle diameter WC powders having a thickness of 0.7 µm, Ni powders having a mean particle diameter of 1.5 µm, and Co powders were wet-mixed at a ratio of 45% by weight, 40% by weight, 7% by weight and 8% by weight, respectively, and molded by pressing. Degassing at 1200 ° C. in a vacuum of ⁻² Torr. Thereafter, the mixture was sintered at 1450 ° C. for 1 hour at a nitrogen gas partial pressure of 30 Torr, and then cooled to 5 ° C./min in vacuum to form Sample 1. Ti content of Sample 1 is 34 weight% in terms of TiCN, W content is 45 weight% in terms of WC, and Ta and Nb content are 6 weight% in terms of TaC + Nb. In addition, N / (C + N) is 0.3 by an atomic ratio. In the area | region of 10 micrometers in thickness from just below a soft layer, WC particle | grains do not exist at all, and at the depth of 1 mm from the outermost surface, the amount of the hard phase containing an internal WC is 15 volume%.

For comparison, Samples 2 to 4 are formed as samples formed by conventional manufacturing methods. Sample 2 is obtained by sintering the same press-formed body as in Sample 1 at 1400 ° C. under a nitrogen partial pressure of 5 Torr. In addition, sample 3 cools the same sintered compact as sample 2 after CO sintering at 200 Torr. In addition, sample 4 cools the same sintered compact as sample 2 after nitrogen sintering at 180 Torr of nitrogen pressure.

The structures of Samples 2 to 4 are 10 vol%, 15 vol% and 5 vol%, respectively, of the hard phase containing WC just below the soft layer. Further, in addition to the same raw material as Sample 1, using TaC, NbC, ZrC, and VC having an average particle diameter of 1 to 3 µm, they were blended in the weight ratio shown in Table 1 below, and a sintered alloy was formed in the same process as Sample 1. It is set as the samples 5-10 with conversion content shown in Table 1. Since Ni, Co, ZrC, and VC are equivalent amounts of compounding composition substantially, description is abbreviate | omitted. In addition, at this time, the atomic ratio of N / (C + N), the thickness of the layer containing 1 wt% or less of the hard phase containing WC just below the soft layer of the alloy surface portion, and the WC at a depth of 1 mm from the outermost surface are contained. The amount of hard phase present is shown in Table 2 below.

The nitrogen-containing sintered hard alloys of each of Samples 1 to 10 were subjected to cutting using the cutting conditions 1 to 3 shown in Table 3 below, and as a result, the determination results shown in Table 4 below were obtained.

As can be seen from the determination results shown in Table 4, when samples 1, 5 and 6 having a composition satisfying the conditions of the first or second aspect of the present invention are used, the composition deviates from the conditions of the present invention. Compared with the samples 2 to 4 and 7 to 10 having the back and the like, both exhibit excellent wear resistance, toughness and thermal shock resistance.

Example 2

Samples 11 to 23 are molded by blending and mixing and pulverizing the raw powders shown in Table 5 to the respective weight-containing weights. Here, the TiCN powder uses an average particle diameter of 2 µm and a C / N atomic ratio of 5/5, and the other powders use an average particle diameter of 1 to 3 µm. Sample 12 used a (TaNb) C powder [TaC: NbC = 2: 1 (weight ratio)] having an average particle diameter of 1.5 mu m as a Ta and Nb source, and Sample 17 had an average particle diameter of 2 mu m as a Ti and W source ( TiW) (CN) powder is used. The compounding quantities of these solid solution raw material powders are shown in Table 5 in terms of single compound. About the compounding composition of each sample, description was abbreviate | omitted since conversion content is substantially the same as a compounding composition.

Sample 11 to 23 10 After heating to 3 ° C./min in a vacuum of Torr, degassing at 1200 ° C. for 15 minutes, sintering at a nitrogen gas partial pressure of 15 to 40 Torr, 1450 ° C. for 1 hour, and then at 1200 ° C. at 3 ° C./min in vacuum Controlled cooling and nitrogen quenching. For samples 11 and 12, after sintering under the same conditions, cooling conditions are changed to form samples 11A to 11C and 12A to 12C. Among them, 11A and 12A were sintered under the same conditions as Samples 11 and 12, and then cooled to CO partial pressure of 150 Torr, cooled to nitrogen partial pressure of 200 Torr for samples 11B and 12B, and up to 1530 ° C for samples 11C and 12C. After the temperature was raised, sintering for 1.5 hours was followed by controlled cooling.

N / (C + N) atomic ratios of samples 11 to 23 and samples 11A to 11C and 12A to 12C, from the thickness and the outermost surface of the region where the hard phase containing WC just below the soft layer of the alloy surface portion is 1% by volume or less; The amount of hard phase containing WC at a depth of 1 mm is shown in Table 6 below.

For each of the samples shown in Table 6, cutting was carried out under cutting conditions 4 to 6 shown in Table 7 below to obtain the determination results shown in Table 8 below. For comparison, cutting tests are also carried out on commercially available coated cemented carbide P grades.

As can be seen from the determination results shown in Table 8, when samples 11, 12, and 13 to 17 having compositions or the like satisfying the conditions of the first or second aspect of the present invention were used, the compositions deviated from the conditions of the present invention. Compared with the samples 11A to 11C, 12A to 12C, and 18 to 23 having the back and the like, all showed excellent wear resistance, toughness and thermal shock resistance.

Example 3

As raw material powders, these raw material powders were prepared using TiCN powder, WC powder, TaC powder, NbC powder, NoC powder, VC powder, (TiWTaNb) CN powder, Co powder and Ni powder having an average particle diameter of 1.5 µm. After blending with the composition shown in the following, mixing for 12 hours in a wet Ato Writer, to produce a CNMG 432-shaped green compact at a pressure of 1.5ton / ㎠, and subjected to the honing treatment, Table 10 Sintered hard alloys having the structures shown in Tables 11 to 13 were prepared under the sintering conditions shown in FIG. In these tables, the "structure from directly below the exudation layer" refers to the composition ratio of the hard phase or the bonded phase that changes with depth toward the inside of the alloy with 0 just under the exudation layer. For example, in Sample No. a-7, the amount of WC immediately under the exudation layer is the average WC volume% of the alloy from just under the exudation layer to the inside, while the amount of the bonding phase is 1.8 vol% to 2.5 μm, and 2.5 μm to 60 μm. It gradually increases between and becomes 60% of the average bonded phase volume of the alloy inside from 60 micrometers. The amount of hard phase in the remainder at each depth is expressed as amount of hard phase = 100-(% of the average bonded phase volume of the alloy)-(average of the WC volume of the alloy).

The samples of a-1 to a-15 are subjected to the thermal shock test under the conditions of (A) and to the abrasion resistance test under the conditions of (b). The results are shown in Table 14.

(A) four workpieces SCM 435 (HB: 250)

Cutting speed 100 (m / min)

Groove 1.5 (mm)

Feed rate 0.20 (mm / rev.)

30 sec cutting time

Wet

(B) Workpiece SCM 435 (HB: 250)

Cutting speed 180 (m / min)

Groove 1.5 (mm)

Feed rate 0.30 (mm / rev.)

Cutting time 20 sec

Wet

In the sintered hard alloy in which TiCN and WC are hard phases, it can be seen that the combination of the exudation layer as specified in the present invention can provide more than the conventional thermal shock resistance. In addition, it can be seen that the wear resistance is improved when there is a binding phase distribution in the specification, and the thermal shock resistance is further improved when there is a WC distribution in the specification.

Example 4

In the same manner as in Example 3, the raw powder was blended in the composition shown in B of Table 9 to form a green compact in the same manner as in Example 3, and after the honing treatment was performed, A sintered alloy of the structure shown in Tables 15 to 17 is formed. Then, the thermal shock resistance test is carried out under the conditions of (C) to the samples of b-1 to b-15, and the wear resistance test is performed under the conditions of (D). The results are shown in Table 18.

(C) workpiece SCM 435 (HB: 300); 4 grooves

Cutting speed 120 ((m / min)

Groove 1.5 (mm)

Feed rate 0.20 (mm / rev.)

30 sec cutting time

Wet

(D) Workpiece SCM 435 (HB: 300)

Cutting speed 200 (m / min)

Groove 1.5 (mm)

Feed rate 0.30 (mm / rev.)

Cutting time 20 sec

Wet

It can be seen that when the 4A, 5A, and 6A groups have a hard phase sintered hard alloy as well as the exudation layer as specified, thermal shock resistance higher than the conventional one is obtained. In addition, it can be seen that abrasion resistance is improved when there is a binding phase distribution in the specification, and that thermal shock resistance can be further improved when there is a WC distribution in the specification.

Example 5

The same raw material powder as in Example 3 was combined with the composition shown in C of Table 9 to form a green compact in the same manner as in Example 3, and after the honing treatment was performed, under the sintering conditions shown in Table 10 A sintered alloy of the structure shown in Tables 19 to 21 is formed. Then, the thermal shock resistance test is carried out under the conditions of (E) to the samples of C-1 to C-15, and the wear resistance test is performed under the conditions of (F). The results are shown in Table 22.

(E) workpiece SCM 435 (HB: 280); 4 grooves

Cutting speed 120 (m / min)

Groove 1.5 (mm)

Feed rate 0.20 (mm / rev.)

30 sec cutting time

Wet

(F) Workpiece SCM 435 (HB: 280)

Cutting speed 200 (m / min)

Groove 1.5 (mm)

Feed rate 0.30 (mm / rev.)

20 min cutting time

Wet

It can be seen that when the sintered hard alloy containing solid solution solid layers of Groups 4A, 5A, and 6A as a raw material is combined with the exudation layer as specified, thermal shock resistance of the prior art can be obtained. In addition, it can be seen that the wear resistance is improved when there is a binding phase distribution in the specification, and the thermal shock resistance is further improved when there is a WC distribution in the specification.

Example 6

The thermal shock resistance test was carried out under the conditions of (G) on the samples a-1 and a-2 shown in Table 11 and d-1 shown in Table 21. The results are shown in Table 23.

(G) Workpiece SCM435 (HB: 280); 4 grooves

Cutting speed 100 (m / min)

Groove 1.5 (mm)

Feed rate 0.20 (mm / rev.)

30 sec cutting time

Wet

For (G), the number of missing cutting blades in the 40 cutting blades is described.

Even if it has an exudation layer, when the layer which has WC as a main component does not exist, it turns out that the improvement of a thermal shock resistance is not recognized.

Claims (12)

(Ti.W _x M _y ) (C _u N _1-u ) (wherein M is at least one of Group 6A metals in the periodic table excluding W, 0x1, 0y ≦ 0.9, and 0u0.9) and WC It contains 75 wt% or more and 95 wt% or less of the hard phase, and contains 5 wt% or more and 25 wt% or less of the combined phase containing Ni, Co and inevitable impurities, and converts Ti into carbides, nitrides or carbonitrides. 5 wt% or more and 60 wt% or less, 30 wt% or more and 50 wt% or less in terms of carbide, 5 wt% or less in terms of carbide, and hard nitrogen / (carbon + nitrogen) in atomic ratio A layer containing at least 0.2 and less than 0.5 and having a soft layer containing a binding phase metal and WC on the outermost surface, and having almost no hard phase containing WC at a thickness of 3 µm or more and 30 µm or less under the soft layer. Having a nitrogen-containing sintered hard alloy. The nitrogen-containing sintered hard alloy according to claim 1, wherein the amount of the hard phase containing WC gradually increases from the layer where the hard phase containing WC is hardly present to the maximum depth of 1 mm from the outermost surface. The nitrogen-containing sintered hard alloy according to claim 1 or 2, wherein the amount of hard phase containing WC is 5 vol% or more and less than 50 vol% in a depth of 1 mm or more from the outermost surface. (TiW _x M _y ) (C _u N _1-u ), wherein M is at least one of Group 4A, 5A, and 6A metals of the periodic table excluding Ti and W, 0x1, 0y≤0.9, 0 u0.9) and a WC-containing hard phase containing at least 75% by weight and at most 95% by weight, containing at least 5% by weight and at most 25% by weight of a binding phase containing NI, Co and unavoidable impurities; 5 wt% or more and 60 wt% or less in terms of nitride or carbonitride, 30 wt% or more and 50 wt% or less in terms of carbide, W 5 wt% or less in terms of carbide, and the total content of Ta and Nb 2% by weight to 15% by weight in terms of carbide, nitride or carbonitride, and 5% by weight or less in terms of carbide, nitride or carbonitride in total content of V, Zr and Hf. Nitrogen) in an atomic ratio of 0.2 or more and less than 0.5, and on the outermost surface there is a soft layer containing the binding phase metal and WC. Jilcheung just below the nitrogen-containing sintered hard alloy having a hard phase containing WC layer with a thickness of less than 30㎛ 3㎛ almost non-existent. 5. The nitrogen-containing sintered hard alloy according to claim 4, wherein the amount of hard phase containing WC gradually increases from the layer in which the hard phase containing WC is hardly present to the maximum depth of 1 mm from the outermost surface. The nitrogen-containing sintered hard alloy according to claim 4 or 5, wherein the amount of hard phase containing WC is 5 vol% or more and less than 50 vol% within 1 mm or more from the outermost surface. Hard phase and Ni. Which contain WC and which contain nitrides, carbonitrides or complex carbonitrides of one or more transition metals selected from Groups 4A, 5A and 6A of the periodic table. In a nitrogen-containing sintered hard alloy having an exudation layer formed over a certain depth from the surface of the alloy and containing an alloyed phase containing Co and unavoidable impurities and an alloy inner layer present directly below the exudation layer, the exudation layer is Ni and Co. The main component contains a metal-bonded phase and WC, and the exudation layer is divided into three layers in the order of the outermost layer and the lowermost middle layer toward the inner direction, and the outermost layer has a WC of more than 0% by volume and 30% by volume or less. Consists of a metal-bonded phase composed mainly of Co and Ni, the middle layer is composed of 50 vol% or more and 100 vol% or less in WC, the remainder is composed of a metallic bonded phase composed of Co and Ni as a main component, and the lowest layer is 0 vol% in WC. More than 30 vol% or less, the remainder being composed of a metal bonded phase containing Co and Ni as main components, the thickness of the outermost layer and the thickness of the lowermost layer being 0.1 µm or more and 10 µm or less, respectively. Having a thickness of more than 0.5㎛ 10㎛ than the nitrogen-containing sintered hard alloy. 8. The alloy inner layer according to claim 7, wherein the alloy inner layer has a region containing no metal-bonded phase containing Co and Ni as a main component or only 2 vol% or less, and has an area of the alloy inner layer directly under the exudation layer of this region. Nitrogen containing sintered hard alloy whose thickness in an inner direction is 2 micrometers or more and 100 micrometers or less. 8. The alloy inner layer according to claim 7, wherein the alloy inner layer has a region containing no WC or only 2% by volume or less, and the thickness of the alloy inner layer from underneath the exudation layer in the inner direction of the alloy inner layer is 1 µm or more. Nitrogen containing sintered hard alloy of 500 micrometers or less. 10. The method according to claim 9, wherein the volume% of WC gradually increases in an inward direction from just under the region containing no WC or only 2 vol% or less of the alloy inner layer, and a depth within 1 mm from just below the exudation layer. A nitrogen-containing sintered hard alloy configured so that the volume% of WC in the alloy inner layer of the alloy becomes the average WC volume% of the entire alloy. 9. The extruded layer according to claim 8, wherein the exudation layer contains a metal-bonded phase containing Ni and Co and WC, and the alloy inner layer contains no WC or only 2 vol% or less of the alloy. A nitrogen-containing sintered hard alloy having a thickness in the inner direction of the alloy inner layer from just below the exudation layer of. 12. The volume percent of WC in the inner direction of the alloy inner layer gradually increases from just below the region containing no WC or only 2 vol% or less of the alloy inner layer, and from 1 below the exudation layer. A nitrogen-containing sintered hard alloy configured such that the volume% of WC in the alloy inner layer within a depth of mm is the average volume% of the entire alloy.