JP2005171283A - Cermet, coated cermet and methods for manufacturing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet excellent in wear resistance and fracture resistance and minimal in finished surface roughness of a workpiece, a coated cermet and methods for manufacturing them. <P>SOLUTION: The cermet consists of 70 to 97wt.% of hard phase composed mainly of titanium carbonitride and comprising at least one kind selected from the carbides, nitrides and carbonitrides of the group IVa, Va and VIa metals of the periodic table and solid solutions thereof and the balance binder phase composed mainly of iron-group metal. The cermet has: a binder-phase layer of 0.3 to 2 μm average thickness composed of the binder phase, in a direction from a case surface toward the inner part; and a binder-phase-decreased layer of 30 to 120μm average thickness in which the amount of the binder phase is decreased as compared with the inner part of the cermet, in a direction from the interface between the binder-phase layer and the binder-phase-decreased layer toward the inner part. Further, the average grain size of the hard phase contained in the binder-phase-decreased layer is 1.0 to 1.2 times the average grain size of the hard phase in the inner part of the cermet. This cermet is reduced in the finished surface roughness of a workpiece, as compared with the conventional cermet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to cermets and coated cermets that are optimal for cutting various work materials such as steel, cast iron, heat-resistant alloys, and non-ferrous alloys, and methods for producing the same.

Cermet cutting tools with high wear resistance and low work surface finish are often used for finishing metal materials. As a conventional cermet, there is a cermet characterized in that the average crystal grain size of the hard phase particles in the surface part of the cermet is larger than the average crystal grain size inside (for example, see Patent Document 1). This cermet is mainly aimed at improving wear resistance, but with the problem of reduced fracture resistance, the hard phase particles on the surface are coarse, so the surface roughness of the cermet increases and the work material There is a problem that the finished surface roughness decreases.

One method for reducing the surface roughness of the work material is to smooth the surface of a cermet cutting tool by grinding or polishing. However, since grinding or polishing is expensive, it may be used with the surface of the cermet being burned. As the surface tempered sintered alloy focusing on the average particle size of the hard phase on the surface of the sintered surface, the average particle size of the hard phase in the surface layer from the sintered surface of the sintered alloy to the inside of 0.05 mm excludes the surface layer. There is a surface tempered sintered alloy characterized in that the average particle size of the hard phase in the sintered alloy is 0.8 to 1.2 times (see, for example, Patent Document 2). Although this surface tempered sintered alloy solves the problems of strength and plastic deformation resistance, it has been unable to meet the recent demand for improvement of the finished surface roughness of the work material.

JP 05-140691 A JP-A-1-287246

In recent years, there has been an increasing demand for processing highly accurate machine parts with high efficiency. Therefore, the cermet cutting tool needs to improve the wear resistance, fracture resistance and work material finished surface quality more than before. The present invention has been made for such a demand, and an object of the present invention is to provide a cermet and a coated cermet having excellent wear resistance and fracture resistance and having a small surface roughness of the work material, and a method for producing them. .

The present inventors have studied for the purpose of obtaining an optimum cermet for a finishing tool, and when an appropriate amount of binder phase is deposited in a layered manner on the surface of the burned surface, the surface of the burned surface becomes smooth and the finished surface roughness is small. The present invention was completed by obtaining the knowledge that forming a binder phase-reduced layer with a reduced binder phase on the inner side of the binder phase layer deposited on the cermet baked skin surface provides superior wear resistance. It has come to be.

That is, the cermet of the present invention is a hard phase composed of at least one selected from carbides, nitrides, carbonitrides and their solid solutions of the periodic table 4a, 5a, 6a group metals mainly composed of titanium carbonitride. A cermet having a burnt skin surface consisting of 70 to 97% by weight and a binder phase comprising at least one selected from iron group metals as a main component: the balance, and facing from the burnt skin surface to the inside. The amount of the binder phase decreased from the interface between the binder phase layer and the binder phase-decreasing layer and the inside of the cermet from the interface between the binder phase layer and the binder phase-decreasing layer. A binder phase-reducing layer having an average thickness of 30 to 120 μm, and the average particle size of the hard phase contained in the binder phase-reducing layer is 1.0 to 1.2 of the average particle size of the hard phase inside the cermet. It is characterized by being double.

The cermet of the present invention is a hard phase composed mainly of Ti carbonitride and comprising at least one selected from carbides, nitrides, carbonitrides and their solid solutions of periodic table 4a, 5a, and 6a metals. : 70 to 97% by weight and a binder phase comprising at least one selected from iron group metals as a main component: the balance.

The hard phase of the cermet of the present invention comprises a composite carbonitride solid solution of titanium and a core portion made of titanium carbonitride and at least one selected from the periodic table 4a, 5a, and 6a metals other than titanium. It consists of a peripheral part. As the form of the hard phase, there are a cored structure in which the periphery surrounds the core, a core single phase consisting of only the core, a peripheral single phase consisting of only the periphery, and the like. Specific examples of titanium carbonitride forming the core include Ti (C, N). Specifically, as a composite carbonitride solid solution of at least one selected from the group 4a, 5a and 6a metals other than titanium forming the peripheral portion and titanium, (Ti, Mo) (C, N), (Ti, Mo, W) (C, N), (Ti, Ta, W, Mo) (C, N), and the like. When the amount of hard phase is less than 70% by weight, the wear resistance is lowered, and when the amount of hard phase exceeds 97% by weight, the remaining binder phase is relatively reduced, so that the fracture resistance is lowered and sintering is performed. Sex is reduced. Therefore, the hard phase was 70 to 97% by weight, and the binder phase was the balance.

The binder phase of the cermet of the present invention is a metal phase mainly composed of at least one selected from iron group metals. Here, the iron group metal means cobalt, iron, or nickel. The hard phase component may be dissolved in the iron group metal constituting the binder phase. In the present invention, the binder phase containing iron group metal as a main component is a solid solution of at least one of iron group metal or periodic table 4a, 5a, 6a metal, carbon, and nitrogen in an amount of 0.1 to 25% by weight. Indicates an iron group metal.

The burnt surface in the cermet of the present invention is a surface state after sintering, or a surface state after washing and drying with water or an organic solvent after sintering, or a burned skin surface by sand blasting, wet blasting or the like after sintering. The surface state from which the deposits are removed can be cited as a representative surface.

In the cermet of the present invention, the burnt skin surface was smoothed by forming a binder phase layer composed of a binder phase having an average thickness of 0.3 to 2 μm from the grilled skin surface to the inside. Here, when the average thickness of the binder phase layer is less than 0.3 μm, the binder phase is difficult to be continuously distributed so as to cover the burnt surface, and the finished surface roughness of the work material after cutting is made uniform. On the contrary, if the thickness exceeds 2.0 μm, the amount of the binder phase in the binder phase reducing layer adjacent to the binder phase layer is remarkably reduced, so that the fracture resistance is lowered and the soft binder phase layer is thick, so that the wear resistance is reduced. descend. Therefore, the average thickness of the binder phase layer was set to 0.3 to 2.0 μm. Among these, 1.0 to 2.0 μm is more preferable. The average thickness of the binder phase layer can be obtained by observing the cross-sectional polished structure with a scanning electron microscope at a magnification of 5000 and measuring 10 or more locations.

A bonded phase-reduced layer having a reduced amount of bonded phase compared to the inside of the cermet was formed adjacent to the bonded phase layer on the burned surface of the cermet of the present invention. The average particle diameter of the hard phase in the binder phase-decreasing layer was 1.0 to 1.2 times the average particle diameter of the hard phase in the cermet excluding the binder phase layer and the binder phase-decreasing layer. This is because when the average particle size of the hard phase in the binder phase-reducing layer is less than 1.0 times, the hardness in the vicinity of the surface is lowered and the wear resistance is lowered, and when it exceeds 1.2 times, the surface roughness of the cermet is exceeded. This is because the finished surface roughness of the work material is increased by increasing the thickness of the work material, and among these, 1.1 to 1.2 times is preferable.

Since the average particle size of the hard phase is almost uniform in the cermet of the present invention and in the binder phase-reduced layer, the binder phase-reduced layer having a reduced amount of the binder phase has high hardness and high wear resistance. Here, if the average thickness of the binder phase-decreasing layer is less than 30 μm, the wear resistance decreases, and if it exceeds 120 μm, the binder phase-decreasing layer having a high hardness becomes thick, so that the strength decreases and the fracture resistance decreases. Therefore, the average thickness of the binder phase reducing layer is set to 30 to 120 μm. Among these, 70-120 micrometers is preferable. The average thickness of the binder phase-decreasing layer can be obtained by quantitatively analyzing the cross-sectional polished structure by EPMA every 5 μm from the interface with the binder phase layer toward the inside.

In the cermet of the present invention, the binder phase-decreasing layer gradually decreases in amount from the inside of the cermet toward the surface, and the amount of binder phase contained in the binder phase-decreasing layer from the interface with the binder phase layer to the inside of 20 μm is the inside of the cermet. It is preferable that it is 0.50 to 0.99 times the amount of the binder phase contained in. When the amount of the binder phase in the binder phase-reduced layer is 0.99 times or less of the amount of the internal binder phase, the wear resistance is improved, but when it is less than 0.50 times, the toughness of the binder phase-reduced layer is markedly reduced. Since it shows the tendency for deficiency to fall, 0.50-0.99 time is preferable. Among these, 0.50 to 0.60 times is more preferable. The amount of the binder phase contained in the binder phase decreasing layer from the interface with the binder phase layer to the inside of 20 μm can be obtained by quantitatively analyzing the cross-sectional polished structure with EPMA.

The average particle size of the hard phase in the cermet of the present invention is preferably 0.5 to 5 μm. This is because the wear resistance tends to be improved when the average particle size of the hard phase is 5 μm or less. However, when the average particle size of the hard phase is less than 0.5 μm, the strength tends to decrease. The average particle diameter of the hard phase can be calculated using image analysis software after observing the cross-sectional polished structure with a scanning electron microscope at a magnification of 5000 and 10 fields of view.

It is preferable to set the hardness inside the cermet of the present invention to HV 1500 to 2200 because the wear resistance is improved. When the hardness inside the cermet is HV1500 or more, the wear resistance is improved, but when it exceeds HV2200, the fracture resistance tends to be lowered.

The arithmetic average roughness Ra of the baked skin surface of the cermet of the present invention is preferably 2 μm or less because the finished surface roughness of the work material is improved. Among them, it is more preferable that the arithmetic average roughness Ra of the grilled skin surface is 0.7 μm or less.

The hardness of the binder phase reduced layer from the interface between the binder phase layer and the binder phase reduced layer in the cermet of the present invention to the inside of 20 μm is preferably 1.01 to 1.10 times the hardness inside the cermet. The thicker the average thickness of the binder phase layer, the higher the hardness of the binder phase reducing layer from the interface of the binder phase layer to the inside of 20 μm. When the hardness of the binder phase reducing layer from the binder phase layer interface to the inside of 20 μm is 1.01 or more times the internal hardness, the wear resistance is improved. On the other hand, if it exceeds 1.10 times, the average thickness of the binder phase layer is increased, and the amount of the binder phase in the binder phase reducing layer adjacent to the binder phase layer is remarkably reduced, so that the defect resistance tends to be lowered.

The coated cermet of the present invention is obtained by coating the surface of the cermet of the present invention with a hard film, and the hard film in the present invention is a periodic table 4a, 5a, 6a metal, aluminum, silicon carbide, nitride, oxide , Borides and their solid solutions, and cubic boron nitride, diamond, and DLC, specifically TiN, TiC, Ti (C, N), (Ti, Al) N, Al ₂ O _{3 and the} like can be mentioned. These hard films can be coated by a conventional physical vapor deposition method or chemical vapor deposition method. It is preferable to coat the surface of the cermet of the present invention with a hard film in order to improve wear resistance.

The cermet of the present invention and the coated cermet of the present invention are preferably used as a cutting tool by taking advantage of high wear resistance and fracture resistance, and more preferably used as a cutting tool for steel processing.

The production method of the cermet of the present invention is as follows. (A) Titanium carbonitride powder 50 to 75% by weight, periodic table 4a, 5a, at least one of the 6a group metal compounds 20 to 40% by weight, iron group metal A mixing step of preparing a mixture consisting of 3 to 20% by weight of at least one of the powders in a total amount of 100% by weight, and (B) the obtained mixture in a vacuum in the range of 1300 to 1440 ° C. A first temperature raising step for raising the temperature to a predetermined temperature; and (C) the mixture is then sintered in a nitrogen atmosphere of 133 to 13300 Pa from a predetermined temperature in the range of 1300 to 1440 ° C. to a sintering temperature in the range of 1450 to 1550 ° C. A second temperature raising step for raising the temperature to (D), and then a sintering step for sintering the mixture at a sintering temperature in the range of 1450 to 1550 ° C. for a predetermined time in a nitrogen atmosphere of 133 to 13300 Pa. , (E A first cooling step of cooling the mixture after sintering at a temperature of 20 ° C. or more per minute from a sintering temperature in the range of 1450 to 1550 ° C. to a predetermined temperature in the range of 1200 to 1330 ° C. in an inert atmosphere; And then holding the mixture for a predetermined time at a predetermined temperature in the range of 1200 to 1330 ° C. in an inert gas atmosphere or vacuum at a lower pressure than in the first cooling step, and (G) then holding the mixture And a second cooling step of cooling from a predetermined temperature in the range of 1200 to 1330 ° C. to room temperature, and a method for producing a cermet.

Each process of the manufacturing method of this invention cermet has the following effects. In the step (A), a mixed powder having a predetermined composition is mixed uniformly. In the step (B), the mixture is heated in a vacuum of 67 Pa or less to promote degassing before and immediately after the appearance of the liquid phase, thereby improving the sinterability. In step (C) and step (D), denitrification from the cermet surface is prevented by a nitrogen atmosphere, the smoothness of the burnt surface accompanying denitrification is reduced, and the hard phase such as Ti (C, N) near the surface is reduced. Suppress. In the step (E), by rapidly cooling from the sintering temperature to the vicinity of the solidification point of the liquid phase, the movement and grain growth of the hard phase particles are suppressed and a smooth cermet surface is maintained. In the step (F), the pressure inside the furnace in the inert gas atmosphere is lowered from that in the step (E) and maintained for a predetermined time, thereby uniformizing the binder phase thickness on the cermet surface.

Specifically, at least one compound selected from the group consisting of 50 to 75% by weight of titanium carbonitride powder, carbides, nitrides, carbonitrides and their solid solutions of the periodic table 4a, 5a and 6a metals A mixing step for obtaining a mixed powder comprising 20 to 40% by weight of the powder and 3 to 20% by weight of the nickel and / or cobalt powder, and a total of 100% by weight, and the mixed powder from room temperature to 1300 to 1440 ° C. First temperature raising step for raising the temperature in a vacuum of 67 Pa or less, an appropriate pressure to suppress denitrification from the cermet by raising the temperature from a predetermined temperature in the range of 1300 to 1440 ° C. to a predetermined temperature in the range of 1450 to 1550 ° C. A second temperature raising step performed in a nitrogen atmosphere of 133 to 13300 Pa, a pressure of 133 to 13300 Pa to suppress denitrification from the cermet at a sintering temperature in the range of 1450 to 1550 ° C. Sintering process for 0.5 to 2 hours in a nitrogen atmosphere and sintering, pressure 133 at a cooling rate of 20 ° C. or more per minute from a predetermined temperature in the range of 1450 to 1550 ° C. to a predetermined temperature in the range of 1200 to 1330 ° C. A first cooling step of cooling in an inert gas atmosphere such as He, Ne, Ar or the like of ˜300000 Pa, an inert gas atmosphere of a pressure 13.3 to 1330 Pa at a predetermined temperature in the range of 1200 to 1330 ° C., or a vacuum of 1 to 130 Pa It is preferable to produce the cermet of the present invention through a holding step of holding for 5 to 30 minutes, and then a second cooling step of cooling to room temperature.

When a hard film is coated on the surface of the cermet obtained by the cermet production method of the present invention by a conventional physical vapor deposition method or chemical vapor deposition method, a coated cermet having excellent wear resistance can be obtained.

The cermet of the present invention is excellent in the finished surface roughness of the work material as compared with the conventional cermet and has wear resistance and fracture resistance equal to or higher than those. A coated cermet coated with a hard film exhibits higher wear resistance. The cermet of the present invention and the coated cermet of the present invention can be produced by the method for producing the cermet of the present invention and the method for producing the coated cermet of the present invention.

Table 1 shows commercially available Ti (C, N) powder (weight ratio TiC / TiN = 50/50), WC, NbC, Mo ₂ C, Ni, and Co having an average particle diameter of 0.8 to 4.0 μm. The mixture was weighed so that the ratio was 5%, and placed in a stainless steel pot together with an acetone solvent and a cemented carbide ball, and mixed and strongly ground. The obtained mixed powder was press-molded at a pressure of 196 MPa using a SPMN120308 shape mold described in JIS-B4120 to produce a molded body.

After charging the compact into the sintering furnace, the temperature was raised from room temperature to 1350 ° C. in a vacuum (Pa) described in Table 2 (b), and the temperature was raised from 1350 ° C. to 1500 ° C. It is performed in a nitrogen atmosphere at a pressure (Pa) described in 2 (c), and held at 1500 ° C. for 1 hour in a nitrogen atmosphere at a pressure (Pa) described in Table 2 (d) to sinter, and 1500 to 1300 Cooled to a temperature of 13 ° C. in an Ar atmosphere of 13300 Pa at the cooling rate described in Table 2 (e) and held at 1300 ° C. in a vacuum (Pa) described in Table 2 (f) for 30 minutes. It cooled to room temperature in atmosphere, and produced the inventive products 1-5 and the comparative products 1-6.

The arithmetic average roughness Ra (μm) on the surface of the burned skin of Invention Products 1 to 5 and Comparative Products 1 to 6 thus obtained was measured with a laser-type non-contact surface roughness meter. The average thickness d3 (μm) of the binder phase layer on the surface of the burnt skin was obtained by observing the cross-sectional polished structure with a scanning electron microscope at a magnification of 5000 and 10 visual fields. In the cross-sectional polished structure, quantitative analysis by EPMA was performed every 5 μm from the interface between the binder phase layer and the binder phase reduced layer to determine the average thickness d2 (μm) of the binder phase reduced layer. The average particle size s1 (μm) of the hard phase inside the cermet and the average particle size s2 (μm) of the hard phase contained in the binder phase-reduced layer are 10 views of the cross-sectional polished structure at 5000 times with a scanning electron microscope, respectively. Observed and calculated using image analysis software. The hard phase particle size ratio s2 / s1 was determined from the obtained s1 and s2. The amount of binder phase a2 (% by weight) contained in the binder phase-decreasing layer from the interface of the binder phase layer to the inside of 20 μm and the amount of binder phase a1 (% by weight) inside the cermet were measured by conducting quantitative analysis of the cross-sectional polished structure with EPMA Then, the binder phase ratio a2 / a1 was determined. The Vickers hardness H1 inside the cermet and the Vickers hardness H2 of the binder phase-decreasing layer from the interface between the binder phase layer and the inside of 20 μm were measured to determine the hardness ratio H2 / H1. These results are listed in Table 3.

The obtained invention products 1 to 5 and comparative products 1 to 6 were ground on the rake face side of the SPMN120308 shape with a # 230 diamond grindstone, and further a chamfer of 0.15 mm × 30 ° at the flank cutting edge ridge line portion. A honing treatment was performed to prepare a cutting test sample. Further, the surface of the sample for cutting test of Invention 1 was coated with a TiAlN film having an average thickness of 3 μm by physical vapor deposition to obtain Invention 6. The following cutting tests 1 and 2 were carried out using the samples for cutting tests of invention products 1 to 6 and comparative products 1 to 6 to measure the flank wear amount, the finished surface roughness of the work material, and the number of defects. The results are shown in Table 4.

Cutting test 1 (Abrasion resistance test)
Material: S45C
Cutting speed: 200m / min
Cutting depth: 0.2mm
Feed: 0.2mm / rev
Cutting oil: WET
Cutting time: 50min
The arithmetic average roughness Ra of the finished surface of the work material was measured every 10 minutes during cutting, and the average value is also shown in Table 4.

Cutting test 2 (Fracture resistance test)
Material: S45C
Cutting speed: 220mm / rev
Cutting depth: 0.5mm
Feed: 0.2mm / rev
Cutting oil: WET
Repeated 5 seconds cutting and 5 seconds pause. The test is completed after 100 repetitions.
The number of tests is 5 times for each sample.

As described above, it can be seen that the inventive product has equivalent or higher wear resistance and fracture resistance than the comparative product, and the finished surface roughness of the work material is small. Inventive products 1 to 5 have an average thickness d3 of the binder phase layer in the range of 1.0 to 2.0 μm and an average thickness d2 of the binder phase reduction layer in the range of 70 to 115 μm. And ratio s2 / s1 of the average particle diameter of the hard phase of a binder phase reduction layer with respect to the average particle diameter of an internal hard phase is 1.1-1.2. For this reason, it has excellent wear resistance with a flank wear amount of 0.19 mm or less and excellent chipping resistance with a number of defects of 1 or less, and the finished surface roughness Ra of the work material is 1.0 μm or less. Excellent work material finish surface quality. Inventive product 6 in which hard product is coated on inventive product 1 has a flank wear amount of 0.13 μm and improved wear resistance.

Claims (9)

A hard phase composed of at least one selected from carbides, nitrides, carbonitrides and solid solutions of the periodic table 4a, 5a, 6a group metals having titanium carbonitride as a main component: 70 to 97% by weight And a binder phase mainly composed of at least one selected from iron group metals: a cermet having a burnt skin surface composed of the balance, and an average consisting of a binder phase from the burnt skin surface toward the inside. Compared to the inside of the cermet, the amount of the binder phase is between the binder phase layer having a thickness of 0.3 to 2 μm and the inside of the cermet from the interface between the binder phase layer and the binder phase reducing layer toward the inside. A binder phase reducing layer having a reduced average thickness of 30 to 120 μm, and an average particle size of the hard phase contained in the binder phase reducing layer is 1.0 to 1 of an average particle size of the hard phase inside the cermet. Cermet that is 2 times. The binder phase decreasing layer gradually decreases in the amount of the binder phase from the inside of the cermet toward the binder phase layer, and the binder phase reducing layer extends from the interface between the binder phase layer and the binder phase reducing layer to the inside of the binder phase by 20 μm. The cermet according to claim 1, wherein the amount of the binder phase contained is 0.50 to 0.99 times the amount of the binder phase inside the cermet. 3. The hardness of the binder phase-decreasing layer from the interface between the binder phase layer and the binder phase-decreasing layer to the inside of 20 μm is 1.01 to 1.10 times the hardness inside the cermet. The stated cermet. The cermet according to any one of claims 1 to 3, wherein an average particle diameter of the hard phase in the cermet is 0.5 to 5 µm. The hardness in the inside of the said cermet is HV1500-2200, The cermet of any one of Claims 1-4. The cermet according to any one of claims 1 to 5, wherein an arithmetic average roughness Ra of the grilled skin surface is 2 µm or less. The coated cermet according to any one of claims 1 to 6, wherein a hard film is coated on a surface of the cermet. In the method for producing cermet, (A) titanium carbonitride powder 50 to 75% by weight, periodic table 4a, 5a, at least one of the group 6a metal compounds 20 to 40% by weight, and iron group metal A mixing step of preparing a mixture consisting of 3 to 20% by weight of at least one powder and a total of 100% by weight, and (B) the obtained mixture in vacuum within a predetermined range of 1300 to 1440 ° C. (C) Then, the mixture is raised from a predetermined temperature in the range of 1300 to 1440 ° C. to a sintering temperature in the range of 1450 to 1550 ° C. in a nitrogen atmosphere of 133 to 13300 Pa. A second temperature raising step for heating, and (D) a sintering step in which the mixture is then sintered for a predetermined time at a sintering temperature in the range of 1450 to 1550 ° C. in a nitrogen atmosphere of 133 to 13300 Pa. E A first cooling step of cooling the mixture after sintering at a temperature of 20 ° C. or more per minute from a sintering temperature in the range of 1450 to 1550 ° C. to a predetermined temperature in the range of 1200 to 1330 ° C. in an inert atmosphere; And then holding the mixture for a predetermined time at a predetermined temperature in the range of 1200 to 1330 ° C. in an inert gas atmosphere or vacuum at a lower pressure than in the first cooling step, and (G) then holding the mixture A second cooling step of cooling from a predetermined temperature in the range of 1200 to 1330 ° C. to room temperature, and a method for producing a cermet. The manufacturing method of the covering cermet which coat | covers a hard film | membrane on the surface of the cermet obtained by the method of Claim 10.