JP3850086B2 - Hard layer coated cermet - Google Patents

Description

で囲まれる範囲内にあることが重要である。
【００１７】
これは、第５ａ族が１原子％未満では耐欠損性、耐摩耗性が不十分となり、２０原子％を越えると焼結性が低下し特に耐欠損性が不十分となるためである。また、第４ａ族が８９原子％を越えると、突発的な欠損が発生し、６０原子％より少ないと塑性変形が大きくなるためである。
【００１８】
一方、サーメット中の窒素量および炭素量は、サーメットの機械的特性、熱的特性を決定する要因として非常に重要であり、特に窒素量が増加するに従い、耐欠損性が向上し、結合金属相への第４ａ族、第５ａ族、第６ａ族金属の固溶量が増加する傾向にあるが、窒素量が過多になると焼成時の結合金属相との濡れの問題で焼結性が低下するという問題が生じる。よって前記硬質相の組成式において窒素量（ｖ）が０．３より小さいと耐欠損性が不十分となり、０．７を越えると焼結体内にボイドが発生し信頼性に欠き、固溶による強化が不十分となる。望ましくは、０．４≦ｖ≦０．６である。
【００１９】
また、窒素、炭素量のＭ1 、Ｍ2 、Ｍ3 の合量に対する比率（ｚ）が０．８より小さいと焼結性が劣化しボイドが残留し、１．０より大きいと遊離炭素が発生するために強度低下を引き起こす結果となる。望ましくは０．８５≦ｚ≦１．０である。
【００２０】
本発明において結合金属相を形成する鉄族金属としては、Ｎｉおよび／またはＣｏが挙げられ、望ましくはＮｉとＣｏから構成され、特にＣｏ／Ｎｉ＋Ｃｏのモル比が０．５〜０．９であることが耐摩耗性向上の点からよい。
【００２１】
上記の本発明のサーメット母材を製造するための方法としては、例えば、まず前述したＴｉ、Ｗ、Ｔａ、Ｎｂ等の周期律表第４ａ、５ａ、６ａ族元素の炭化物、窒化物、炭窒化物の粉末および鉄族金属粉末を最終焼結体が上述した割合に成るように秤量混合した後にプレス成形、押し出し成形、射出成形等の成形手段で成形後、焼成する。
【００２２】
焼成は、真空中あるいは還元性雰囲気中で１４００〜１８００℃の温度で行う。焼結中の任意の温度において、Ｎ₂ 、ＣＯ、Ａｒ、Ｈｅなどのガスを０〜７６０Ｔｏｒｒ導入して雰囲気調整を行うこともある。
【００２３】
特に、結合金属相に対する第４ａ族、第５ａ族、第６ａ族元素の固溶量を前述したように増量させるには、１２００〜１４００℃の液相出現温度前後で保持することで結合金属相中への遷移金属の固溶量を制御でき、その保持時間が長いほど固溶量を増加させることができる。特に０．５〜５時間の範囲が適当である。
【００２４】
また、上記の１２００〜１４００℃の温度域での保持のかわりに、１５℃／ｍｉｎ以下の速度でゆっくり昇温して調整してもよい。また、調合時の炭化物、窒化物、炭窒化物中の含有炭素量、窒素量を調製することでも遷移金属の固溶量を制御できる。
【００２５】
また、焼成最高温度では、焼結体の表面の荒れを抑制するために、焼成温度到達前および到達後０．５〜２時間程は窒素圧１〜１００ｔｏｒｒの雰囲気で焼成した後、真空中で０．１〜１時間程度保持するのがよい。
【００２６】
また、本発明によれば、上記の系に対して特性を改善する目的でさらにＺｒ、Ｈｆ、Ｃｒ、およびＶ等の炭化、窒化物、炭窒化物等を添加して特性の改善を図ることができる。
【００２７】
また、本発明によれば、上記の構成からなる強靱性を有するサーメットを母材として、その表面に周期律表第４ａ族元素、Ａｌの炭化物、窒化物、炭窒化物、酸化物のうちの少なくとも１種からなる硬質層を被覆してなる。具体的には、ＴｉＣ，ＴｉＣＮ，ＴｉＮ、Ａｌ₂ Ｏ₃ ，ＴｉＡｌＮ、ＴｉＡｌＯＮ等が好適であり、これらは単層あるいは複数の層により構成することができる。望ましくは、母材側から、最下層をＴｉＮ層とするのがよい。これは、脆化層の生成を抑制すると同時に、付着強度の向上を図ることができるためである。この硬質層は、全体厚みとして、０．５〜１０μｍの厚みで形成するのがよい。
【００２８】
【実施例】
原料粉末としてＴｉＮ、ＴｉＣＮ、ＷＣ、ＴａＣ、ＮｂＣ、Ｍｏ₂ Ｃ、ＶＣ、Ｎｉ、Ｃｏの各粉末を用いて組成が表１の割合に成るように秤量混合した後、１．５ｔｏｎ／ｃｍ² の圧力でＳＤＫＮ１２０３用のフライスチップ形状にプレス成形し、これを真空炉に入れ、窒素圧２０ｔｏｒｒ中で徐々に昇温して１３５０℃での保持時間を表１のように設定し、さらに最高温度で１〜２時間保持し、後半の３０分を真空に戻して保持した後、放冷した。得られた焼結体は、いずれも表面の滑らかな良好な表面を有していた。そして、得られたサーメット焼結体の表面にＣＶＤ法によって、表１に示す層構成からなる硬質層を形成した。
【００２９】
得られたサーメット焼結体に対しては、結合金属相に固溶する第４ａ族、第５ａ族、第６ａ族金属量を測定した。測定は、焼結体を粉砕後、塩酸で結合金属相のみを選択的に溶解した後、該溶液をＩＣＰ発光分光分析にて定量し、結果は表２に示す。
【００３０】
また、作製した硬質層被覆サーメットに対して、下記に示す切削条件で切削試験を行い、切削性能の確認を行った。欠損までの衝撃回数とフランク摩耗量を調べ結果は表２に示した。
【００３１】
（断続試験）
被削材 ＳＣＭ４４０Ｈ
切削速度 ２００ｍ／ｍｉｎ
切り込み ２ｍｍ
送り ０．２６ｍｍ／ｔｏｏｔｈ
（摩耗試験）
被削材 Ｓ５０Ｃ
切削速度 ２５０ｍ／ｍｉｎ
切り込み ２ｍｍ
送り ０．２ｍｍ／ｔｏｏｔｈ
【００３２】
【表１】

【００３３】
【表２】

【００３４】
表１、２の結果から明らかなように、結合金属相への固溶量を１０〜４０原子％とし、各遷移金属の固溶比率が点Ａ、Ｂ、Ｃ、Ｄの範囲にある試料Ｎo.１〜８は、耐欠損性までの衝撃回数も１０００回を越えるものであり、しかも摩耗量も０．１０ｍｍ以下と優れたものであった。
【００３５】
これに対して、結合金属相中への遷移金属の固溶量が４０原子％よりも多い試料Ｎo.１３では焼結性が悪いために耐欠損性、耐摩耗性が大きく劣化し、固溶量が１０原子％よりも少ない試料Ｎo.１２では、一次境界部が異常摩耗した。
【００３６】
また、固溶量が１０〜４０原子％の範囲であっても、点Ａ、Ｂ、Ｃ、Ｄの範囲から逸脱する試料Ｎo.９〜１１では、いずれも本発明品のような優れた耐欠損性と耐摩耗性は得られなかった。
【００３７】
【発明の効果】
以上詳述した通り、本発明の硬質層被覆サーメットは、母材となるサーメットの結合金属相中に多量の遷移金属を特定比率で固溶させることにより、母材自体の耐欠損性、耐熱衝撃性を大幅に改善し、しかもその表面に硬質層を有することから、切削工具として優れた耐摩耗性を有するとともに、耐欠損性を改善することができ、切削特性の向上を図ることができる。
【図面の簡単な説明】
【図１】本発明の硬質層被覆サーメットにおける結合金属相中の第４ａ族、第５ａ族、第６ａ族金属の固溶量を示す３元図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cermet excellent in thermal shock resistance, fracture resistance, and wear resistance, and particularly to a hard layer-coated cermet excellent in interrupted cutting performance when used as a cutting tool material.
[0002]
[Prior art]
In recent years, a cermet composed of a hard phase composed of double carbonitrides of Group 4a, 5a, and 6a elements of the periodic table and a bonded metal phase composed of an iron group metal is widely used for cutting tool materials, wear resistant tool materials, and the like. It has been. As such a cermet, a TiC-based cermet mainly composed of TiC has been mainstream so far, but this TiC-based cermet is inferior in toughness compared to a cemented carbide that has been used as a tool material for a long time. A so-called TiCN-based cermet was proposed in which the toughness was improved by adding nitride to this system.
[0003]
A typical example of this TiCN-based cermet is JP-B-56-51201, which is composed of a hard phase composed of (Ti, W, Ta, Mo) CN and a bonded metal phase composed of Ni and Co. Cermet is disclosed, and it is stated that the hard phase exhibits a cored structure composed of a core rich in Ti and nitrogen and a peripheral part rich in W, Ta, Mo and carbon.
[0004]
Carbon (C) and nitrogen (N) forming the hard phase are major factors that determine the toughness and hardness of the cermet. Recently, attempts have been made to increase the toughness of the cermet by containing a large amount of nitrogen. Has been made.
[0005]
However, recently, improvements have been made to further improve wear resistance and toughness by changing the structure of the surface portion of the TiCN-based cermet. For example, in Japanese Patent Publication No. 59-14534, a softened layer rich in toughness is formed on the surface of the sintered body by introducing nitrogen into the furnace at a temperature lower than the liquid phase appearance temperature during firing. It has been proposed to form a layer having a higher hardness than the inside by firing in a reducing atmosphere containing CO.
[0006]
In order to further improve the wear resistance of these cermets, Group 4a elements of the periodic table such as TiC, TiN, TiCN, Al ₂ O ₃ or Al oxides, nitrides, carbides, carbonitrides, etc. It has also been proposed to coat.
[0007]
[Problems to be solved by the invention]
However, conventional cermets have only improved either wear resistance or fracture resistance, and have not yet satisfied both characteristics. In particular, cutting tools are required to have higher wear resistance and fracture resistance due to higher toughness due to higher temperatures due to high-speed cutting and thermal shocks associated therewith.
[0008]
Although the wear resistance can be solved to some extent by coating the surface with a hard layer, etc., if the toughness of the base material to be coated is low, the hard layer and the base material are subjected to a large thermal shock or mechanical shock. In some cases, the cutting edge of the material was damaged, making it impossible to use.
[0009]
Therefore, an object of the present invention is to provide a hard layer-covered cermet having excellent wear resistance and fracture resistance by forming a hard layer on the surface of a base material made of tough cermet.
[0010]
[Means for Solving the Problems]
The inventor has repeatedly studied the above-mentioned problems, and in particular, as a result of studying a method for improving the thermal shock resistance and fracture resistance of the cermet as a base material, the bonded metal phase composed of an iron group metal is obtained. By actively solid-dissolving Group 4a, 5a and 6a metals of the periodic table of the hard phase component, the fracture resistance and thermal shock resistance of the cermet can be dramatically improved, thereby making the hard layer In the case of coating, it was found that an excellent cutting tool having both excellent wear resistance and fracture resistance was obtained, and the present invention was achieved.
[0011]
That is, the hard layer-covered cermet of the present invention includes one or more of Ti carbide, nitride and carbonitride, and carbides, nitrides and carbonitrides of Group 4a, 5a and 6a metals of the periodic table excluding Ti. 1 to 2 or more selected from the above (excluding the combination of carbide alone or nitride alone) in a total of 70 to 95% by weight and iron group metal in a proportion of 5 to 30% by weight On the surface of the cermet base material comprising a hard phase composed of carbonitrides of Group 4a, 5a, and 6a metals of the periodic table and a bonded metal phase containing iron group metals. In the hard layer-covered cermet formed by coating a hard layer made of at least one of Group 4a element, Al carbide, nitride, carbonitride, and oxide, a period is formed in the bonded metal phase of the base material. Tables 4a, 5a, 6a metals in total 10 to 40 atoms %, And the ratio by the atomic ratio of Group 4a, 5a, and 6a metals of the periodic table in which the solid solution is formed is the following points A, B, C, and D in the ternary diagram of FIG.
Group 4a Group 5a Group 6a
Point A 89 1 10
Point B 60 1 39
Point C 60 20 20
Point D 70 20 10
In addition, the lowermost layer of the hard layer is formed of a TiN layer .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The cermet base material in the present invention is selected from one or more of Ti carbide, nitride, and carbonitride, and carbides, nitrides, and carbonitrides of Group 4a, 5a, and 6a metals except for Ti. 1 to 2 or more (excluding a combination of carbide alone or nitride alone) in a total amount of 70 to 95% by weight and an iron group metal in a proportion of 5 to 30% by weight. It is fired and is composed of a hard phase composed of carbonitrides of Group 4a, 5a, and 6a metals of the periodic table and a bonded metal phase containing an iron group metal.
[0013]
In particular, as a hard phase forming component, it is desirable to contain W, Ta, and Nb as essential components in addition to Ti. The composition of the cermet in terms of the atomic ratio of the hard phase is [(M1) a (M2) b (M3) c] (CuNv) z (wherein M1 is Group 4a, M2 is Group 5a, M3 is Each of group 6a elements))
0.75 ≦ a ≦ 0.95
0.05 ≦ b + c ≦ 0.25
0 <b / (b + c) ≦ 0.95, a + b + c = 1
0.30 ≦ v ≦ 0.70, u + v = 1
0.80 ≦ z ≦ 1.0
Is satisfied. In particular, M1 is mainly composed of Ti, it is desirable to make Ta essential as M2, and W essential as M3. Furthermore, the amount of Ti in (M1) relative to (a + b + c) is It is desirable that a is 0.85 ≦ a ≦ 0.92.
[0014]
In the above composition range, when a is smaller than 0.75 or (b + c) is larger than 0.25, the sinterability is lowered, and the solid solution of the transition metal element in the bonded metal phase tends to be insufficient. When a is larger than 0.95 or (b + c) is smaller than 0.05, improvement in fracture resistance cannot be expected so much. Moreover, when b / (b + c) exceeds 0.95, the sinterability tends to decrease.
[0015]
A major feature of the cermet of the present invention is that the group 4a, group 5a, and group 6a metal content in the entire bonded metal phase is 10 to 40 atomic%, particularly 15 to 35 atomic%. It exists in comparison with the amount of solid solution (about 1-5 atomic%). If the amount of this solid solution is less than 10 atomic%, the solid solution strengthening is insufficient and sufficient fracture resistance cannot be obtained, and if it exceeds 40 atomic%, the sinterability is lowered and the fracture resistance is drastically lowered.
[0016]
In particular, the composition ratios of groups 4a, 5a, and 6a of the periodic table to be dissolved are the following points A, B, C, and D in the ternary diagram of FIG.

It is important to be within the range surrounded by.
[0017]
This is because if the group 5a is less than 1 atomic%, the fracture resistance and wear resistance are insufficient, and if it exceeds 20 atomic%, the sinterability is lowered and the fracture resistance is particularly insufficient. Further, if the group 4a exceeds 89 atomic%, sudden defects occur, and if it is less than 60 atomic%, plastic deformation increases.
[0018]
On the other hand, the amount of nitrogen and carbon in the cermet is very important as a factor that determines the mechanical and thermal properties of the cermet. In particular, as the amount of nitrogen increases, the fracture resistance improves and the bonded metal phase increases. However, if the amount of nitrogen is excessive, the sinterability decreases due to the problem of wetting with the bonded metal phase during firing. The problem arises. Therefore, if the nitrogen content (v) is less than 0.3 in the composition formula of the hard phase, the fracture resistance becomes insufficient, and if it exceeds 0.7, voids are generated in the sintered body and the reliability is lacking. Strengthening is insufficient. Desirably, 0.4 ≦ v ≦ 0.6.
[0019]
Also, if the ratio (z) of the total amount of nitrogen and carbon to M1, M2 and M3 is less than 0.8, the sinterability deteriorates and voids remain, and if it exceeds 1.0, free carbon is generated. This results in a decrease in strength. Desirably, 0.85 ≦ z ≦ 1.0.
[0020]
In the present invention, examples of the iron group metal that forms the binding metal phase include Ni and / or Co. Desirably, the iron group metal is composed of Ni and Co, and particularly the molar ratio of Co / Ni + Co is 0.5 to 0.9. From the point of improving wear resistance.
[0021]
Examples of the method for producing the cermet base material of the present invention include, for example, the carbides, nitrides, and carbonitrides of elements 4a, 5a, and 6a of the periodic table such as Ti, W, Ta, and Nb described above. The product powder and the iron group metal powder are weighed and mixed so that the final sintered body has the above-mentioned ratio, and then molded by a molding means such as press molding, extrusion molding, injection molding, and the like, and then fired.
[0022]
Firing is performed at a temperature of 1400 to 1800 ° C. in vacuum or in a reducing atmosphere. At any temperature during sintering, some N _2, CO, Ar, also make gas atmosphere adjusted by introducing 0~760Torr the like He.
[0023]
In particular, in order to increase the solid solution amount of the Group 4a, 5a, and 6a elements in the bonded metal phase as described above, the bonded metal phase is maintained by maintaining the liquid phase appearance temperature at 1200 to 1400 ° C. The amount of transition metal dissolved therein can be controlled, and the solid solution amount can be increased as the retention time is longer. A range of 0.5 to 5 hours is particularly suitable.
[0024]
Further, instead of holding in the temperature range of 1200 to 1400 ° C., the temperature may be slowly raised at a rate of 15 ° C./min or less. Moreover, the solid solution amount of the transition metal can also be controlled by adjusting the carbon content and nitrogen content in the carbide, nitride, and carbonitride during blending.
[0025]
At the highest firing temperature, in order to suppress the surface roughness of the sintered body, after firing in an atmosphere with a nitrogen pressure of 1 to 100 torr for 0.5 to 2 hours before reaching the firing temperature and after reaching the firing temperature, It is good to hold for about 0.1 to 1 hour.
[0026]
In addition, according to the present invention, for the purpose of improving the characteristics of the above system, carbonization, nitride, carbonitride, etc. such as Zr, Hf, Cr, and V are further added to improve the characteristics. Can do.
[0027]
Further, according to the present invention, a cermet having toughness having the above-described structure is used as a base material, and the surface of the group 4a element of the periodic table, Al carbide, nitride, carbonitride, oxide is selected from the surface. A hard layer made of at least one kind is coated. Specifically, TiC, TiCN, TiN, Al ₂ O ₃ , TiAlN, TiAlON, and the like are suitable, and these can be composed of a single layer or a plurality of layers. Desirably, the lowermost layer is a TiN layer from the base material side. This is because the formation of the embrittled layer can be suppressed and at the same time the adhesion strength can be improved. The hard layer is preferably formed with a total thickness of 0.5 to 10 μm.
[0028]
【Example】
After using a powder of TiN, TiCN, WC, TaC, NbC, Mo ₂ C, VC, Ni, and Co as a raw material powder so that the composition is in the ratio shown in Table 1, it is 1.5 ton / cm ² . Press-molded into a milling chip shape for SDKN1203 under pressure, put it in a vacuum furnace, gradually raise the temperature in a nitrogen pressure of 20 torr, set the holding time at 1350 ° C. as shown in Table 1, and at the maximum temperature After holding for 1-2 hours, the latter half of 30 minutes was returned to vacuum and then allowed to cool. Each of the obtained sintered bodies had a good surface with a smooth surface. And the hard layer which consists of a layer structure shown in Table 1 was formed in the surface of the obtained cermet sintered compact by CVD method.
[0029]
For the obtained cermet sintered body, the amount of Group 4a, Group 5a, and Group 6a metals dissolved in the bonded metal phase was measured. In the measurement, after the sintered body was pulverized and only the bonded metal phase was selectively dissolved with hydrochloric acid, the solution was quantified by ICP emission spectroscopic analysis, and the results are shown in Table 2.
[0030]
Moreover, the cutting test was performed on the produced hard layer-covered cermet under the following cutting conditions to confirm the cutting performance. Table 2 shows the results of the investigation of the number of impacts to failure and the amount of flank wear.
[0031]
(Intermittent test)
Work Material SCM440H
Cutting speed 200m / min
Notch 2mm
Feed 0.26mm / tooth
(Abrasion test)
Work material S50C
Cutting speed 250m / min
Notch 2mm
Feed 0.2mm / tooth
[0032]
[Table 1]

[0033]
[Table 2]

[0034]
As is apparent from the results of Tables 1 and 2, the sample No in which the solid solution amount in the bonded metal phase is 10 to 40 atomic% and the solid solution ratio of each transition metal is in the range of points A, B, C and D. In Nos. 1 to 8, the number of impacts until fracture resistance exceeded 1000, and the amount of wear was excellent at 0.10 mm or less.
[0035]
On the other hand, the sample No. 13 in which the amount of the transition metal dissolved in the bonded metal phase is larger than 40 atomic% is poor in sinterability, so that the fracture resistance and wear resistance are greatly deteriorated. In sample No. 12, the amount of which was less than 10 atomic%, the primary boundary part was abnormally worn.
[0036]
Further, even when the solid solution amount is in the range of 10 to 40 atomic%, all of the samples No. 9 to 11 deviating from the range of points A, B, C, and D have excellent resistance to resistance as in the present invention product. Defects and wear resistance were not obtained.
[0037]
【The invention's effect】
As described above in detail, the hard layer-coated cermet of the present invention is formed by dissolving a large amount of transition metal in a specific ratio in the binding metal phase of the cermet that is the base material, thereby preventing the fracture resistance and thermal shock of the base material itself. Since it has a hard layer on the surface thereof, it has excellent wear resistance as a cutting tool, can be improved in chipping resistance, and can improve cutting characteristics.
[Brief description of the drawings]
FIG. 1 is a ternary diagram showing solid solution amounts of Group 4a, Group 5a, and Group 6a metals in a bonded metal phase in a hard layer-covered cermet of the present invention.

Claims (1)

One or more of Ti carbides, nitrides, carbonitrides and one or more selected from carbides, nitrides, carbonitrides of Group 4a, 5a, and 6a metals of the periodic table excluding Ti ( However, a combination of 70 to 95% by weight in total and 5 to 30% by weight of an iron group metal is calcined, except for a combination of carbide alone or nitride alone. On the surface of the cermet base material composed of a hard phase composed of a carbonitride of Group 4a, 5a, 6a metal and a bonded metal phase containing an iron group metal, Group 4a element of the periodic table, Al carbide, nitride In the hard layer-covered cermet formed by coating a hard layer made of at least one of a metal, a carbonitride, and an oxide, the metals in groups 4a, 5a, and 6a of the periodic table are included in the bonded metal phase of the base material. It is solid solution at a ratio of 10 to 40 atomic% in total, and is solid solution In the ternary diagram of FIG. 1, the ratios according to the atomic ratio of Group 4a, 5a, and 6a metals in the periodic table are as follows: A, B, C, D
Group 4a Group 5a Group 6a
Point A 89 1 10
Point B 60 1 39
Point C 60 20 20
Point D 70 20 10
A hard layer-covered cermet characterized in that the lowermost layer of the hard layer is formed of a TiN layer .

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