JP4013238B2 - Method of manufacturing a surface-coated tungsten carbide-based cemented carbide cutting tool that exhibits excellent fracture resistance in intermittent heavy cutting - Google Patents
Method of manufacturing a surface-coated tungsten carbide-based cemented carbide cutting tool that exhibits excellent fracture resistance in intermittent heavy cutting Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
この発明は、特に鋼などの断続切削を高送りや高切り込みなどの重切削条件で行った場合にすぐれた耐欠損性を発揮する表面被覆炭化タングステン基超硬合金製切削工具（以下、被覆超硬工具という）の製造方法に関するものである。
【０００２】
【従来の技術】
従来、一般に、結晶成長が等方性の炭化タングステン（ＷＣで示す）相：８５〜９５重量％を含有し、残りがＣｏを主体とする結合相と不可避不純物からなる組成を有する炭化タングステン基超硬合金基体（以下、超硬基体という）の表面に、炭化チタン（以下、ＴｉＣで示す）層、窒化チタン（以下、同じくＴｉＮで示す）層、炭窒化チタン（以下、ＴｉＣＮで示す）層、炭酸化チタン（以下、ＴｉＣＯで示す）層、および炭窒酸化チタン（以下、ＴｉＣＮＯで示す）層のうちの１種の単層または２種以上の複層からなるＴｉ化合物層、あるいは前記Ｔｉ化合物層と酸化アルミニウム（以下、Ａｌ2Ｏ3で示す）層とで構成された硬質被覆層を４〜１５μｍの平均層厚で化学蒸着および／またわ物理蒸着してなる被覆超硬工具が知られており、この被覆超硬工具は主に鋼などの連続切削や断続切削に用いられる。
また、一般に上記の被覆超硬工具の硬質被覆層を構成するＡｌ2Ｏ3層として、α型結晶構造をもつものやκ型結晶構造をもつものなどが広く実用に供され、さらに上記ＴｉＣＮ層には、粒状結晶組織をもつものの他に、例えば特開平６−８０１０号公報や特開平７−３２８８０８号公報などに記載される通り、通常の化学蒸着装置にて、反応ガスとして有機炭窒化物を含む混合ガスを使用し、７００〜９５０℃の中温温度域で化学蒸着することにより縦長成長結晶組織をもつようにしたものも知られている。
【０００３】
【発明が解決しようとする課題】
一方、近年の切削加工に対する省力化および省エネ化、さらに低コスト化の要求は強く、これに伴い、切削加工は、高送りおよび高切り込みなどの重切削条件で行われる傾向にあるが、上記の従来被覆超硬工具においては、特にこれを断続切削を高送りおよび高切り込みなどの重切削条件で行うのに用いると、切刃に欠けが発生し易く、これが原因で比較的短時間で使用寿命に至るのが現状である。
【０００４】
【課題を解決するための手段】
そこで、本発明者等は、上述のような観点から、上記の従来被覆超硬工具の耐欠損性向上を図るべく研究を行った結果、
上記の従来被覆超硬工具を構成する超硬基体、すなわち結晶成長が等方性のＷＣ相によって構成された超硬基体は、通常、所定の配合組成の混合粉末よりプレス成形された圧粉体を、例えば１０-2〜１０-6Ｔｏｒｒの真空雰囲気中、１３００〜１５００℃の温度に昇温し、この昇温温度に１〜３時間保持後炉冷の条件で焼結することにより製造されているが、この従来超硬基体の焼結工程での昇温に際して、８００〜１２００℃に昇温した時点で、まず、その雰囲気を、真空からそれぞれＨ2とＣＯ2の分圧を１〜２０Ｔｏｒｒとした脱炭雰囲気とし、この脱炭雰囲気に所定時間保持した後、温度は同じく８００〜１２００℃に保持したままで、その雰囲気をそれぞれの分圧がＨ2：１〜２０Ｔｏｒｒ、ＣＨ4：１〜２０ＴｏｒｒのＨ2とＣＨ4の混合ガスからなる浸炭雰囲気とし、この浸炭雰囲気に所定時間保持する脱炭・浸炭処理を施す（ただし、前記脱炭・浸炭処理後の焼結温度への昇温、前記焼結温度での保持、および炉冷の雰囲気は、上記の通りの真空雰囲気中で行われる）と、焼結後の超硬基体の表面部には、ＷＣのもつ六方晶結晶構造の[００１]面が優先的に成長して偏平化した形状の異方性ＷＣ相が存在した表面層が形成されるようになり、このように偏平化したＷＣ相は、等方性（粒状）のＷＣ相に比して結合相との結合界面が増加したものになるから、前記異方性（偏平状）ＷＣ相が存在する表面層は靭性の向上したものになり、しかもこの場合前記脱炭・浸炭温度を調整し、基体表面を光学顕微鏡で観察して、前記異方性ＷＣ相が前記等方性ＷＣ相との合量に占める割合で２０〜６０面積％存在するようにすると共に、前記脱炭・浸炭時間をそれぞれ１０〜３０分の範囲で調整して、前記異方性ＷＣ相が基体表面から５０〜５００μｍの深さに亘って存在するようにすると、この結果の超硬基体の表面部に形成された前記表面層はきわめて高い靭性をもつようになることから、これに上記の硬質被覆層を形成してなる被覆超硬工具は、これを高靭性が要求される鋼の断続重切削に用いても切刃に欠けの発生なく、切削性能を長期に亘って発揮するという研究結果を得たのである。
【０００５】
この発明は、上記の研究結果に基づいてなされたものであって、
（ａ）ＷＣ相：８５〜９５重量％を含有し、残りがＣｏを主体とする結合相と不可避不純物からなる組成を有する超硬基体の表面に、ＴｉＣ層、ＴｉＮ層、ＴｉＣＮ層、ＴｉＣＯ層、ＴｉＮＯ層、およびＴｉＣＮＯ層のうちの１種の単層または２種以上の複層からなるＴｉ化合物層、あるいは前記Ｔｉ化合物層とＡｌ2Ｏ3層で構成された硬質被覆層を４〜１５μｍの平均層厚で化学蒸着してなる被覆超硬工具を構成する前記超硬基体の１０ −２ 〜１０ −６ Ｔｏｒｒの真空雰囲気中での焼結工程において、
（ｂ）１３００〜１５００℃の範囲内の所定の焼結温度への昇温に際して、まず、８００〜１２００℃の範囲内の所定の温度に昇温した時点で、その雰囲気を真空からそれぞれの分圧がＨ ２ ：１〜２０Ｔｏｒｒ、ＣＯ ２ ：１〜２０ＴｏｒｒのＨ ２ とＣＯ ２ の混合ガスからなる脱炭雰囲気とし、この脱炭雰囲気に所定時間保持した後、温度は同じく８００〜１２００℃の範囲内の所定の温度に保持したままで、その雰囲気をそれぞれの分圧がＨ ２ ：１〜２０Ｔｏｒｒ、ＣＨ ４ ：１〜２０ＴｏｒｒのＨ ２ とＣＨ ４ の混合ガスからなる浸炭雰囲気とし、この浸炭雰囲気に所定時間保持する脱炭・浸炭処理を施すことにより、
（ｃ）上記超硬基体の表面部に、基体表面を光学顕微鏡で観察して、ＷＣのもつ六方晶結晶構造の[００１]面が優先的に成長して偏平化した形状の異方性ＷＣ相がＷＣ相に占める割合で２０〜６０面積％存在し、残りが上記等方性のＷＣ相からなる組織を示し、かつ前記異方性ＷＣ相が表面から５０〜５００μｍの深さに亘って存在する表面靭性層を形成してなる、
断続重切削ですぐれた耐欠損性を発揮する被覆超硬工具の製造方法に特徴を有するものである。
【０００６】
なお、この発明の被覆超硬工具において、これを構成する超硬基体の表面部に形成した表面靭性層の基体表面における異方性ＷＣ相の割合を、ＷＣ相に占める割合で２０〜６０面積％としたのは、その割合が２０面積％未満では基体表面部に所望の靭性を確保することができず、一方その割合が６０面積％を越えると、靭性は一段と向上するが、反面熱塑性変形し易く、特に熱発生の著しい乾式断続重切削では切刃に偏摩耗が起り、これが原因で使用寿命に至ることから、その割合を２０〜６０面積％、望ましくは２５〜５０％と定めた。
また、上記の表面靭性層の基体表面からの深さを５０〜５００μｍとしたのも同じ理由からで、その深さが５０μｍ未満では基体表面部に所望の靭性を確保することができず、一方その深さが５００μｍを越えると、切刃が熱塑性変形し易くなって使用寿命に至るものであり、望ましくは１００〜３００μｍとするのがよい。
【０００７】
さらに、この発明の被覆超硬工具を構成する超硬基体におけるＷＣ相の割合を、８５〜９５重量％としたのは、その割合が８５重量％未満では相対的に結合相の割合が多くなり過ぎて基体自体の耐摩耗性が急激に低下するようになり、一方その割合が９５重量％を越えると、反対に結合相の割合が少なくなり過ぎて強度が低下するようになるという理由によるものである。
また、硬質被覆層の平均層厚を４〜１５μｍとしたのは、その平均層厚が４μｍ未満では、所望の耐摩耗性を確保することができず、一方その平均層厚が１５μｍを越えると、切刃に欠けやチッピングが発生し易くなるという理由からである。
【０００８】
【発明の実施の形態】
つぎに、この発明の被覆超硬工具を実施例により具体的に説明する。
原料粉末として、平均粒径：３μｍのＷＣ粉末、同１μｍのＣｒ3Ｃ2粉末、および同３μｍのＣｏ粉末を用意し、これら原料粉末を表１に示される配合組成に配合し、ボールミルで７２時間湿式混合し、乾燥した後、この混合粉末をＩＳＯ規格ＣＮＭＧ１２０４０８に則したスローアウエイチップ形状の圧粉体にプレス成形し、これらのの圧粉体を１０-3ｔｏｒｒの真空雰囲気中、８００〜１２００℃の範囲内の所定の温度に昇温した時点で、まず、その雰囲気を、真空からＨ2：１０Ｔｏｒｒ、ＣＯ2：１０Ｔｏｒｒの分圧のＨ2とＣＯ2の混合ガスからなる脱炭雰囲気とし、この脱炭雰囲気に２０分保持した後、温度は同じく８００〜１２００℃の範囲内の所定の温度に保持したままで、その雰囲気をそれぞれの分圧がＨ2：１０Ｔｏｒｒ、ＣＨ4：１０ＴｏｒｒのＨ2とＣＨ4の混合ガスからなる浸炭雰囲気とし、この浸炭雰囲気にも２０分保持する脱炭・浸炭処理を施し、この後雰囲気を１０-3ｔｏｒｒの真空雰囲気として、１４００〜１４６０℃の範囲内の所定の温度に昇温し、以降前記の真空雰囲気を保持したままで、この昇温温度に１時間保持し、炉冷することにより超硬基体Ａ〜Ｇをそれぞれ製造した。
さらに、比較の目的で、表２に示される通り、上記の超硬基体Ａ〜Ｇの製造における昇温過程での上記脱炭・浸炭処理を行わず、焼結温度までの昇温を上記の１０-3ｔｏｒｒの真空雰囲気中で行う以外は同一の条件で超硬基体ａ〜ｇをそれぞれ製造した。
上記の超硬基体Ａ〜Ｇおよび超硬基体ａ〜ｇのそれぞれについて、その表面を光学電子顕微鏡（５０００倍）により観察し、ＷＣ相の全体割合、並びにＷＣ相に占める異方性ＷＣ相および等方性ＷＣ相の割合を画像解析装置を用いて測定すると共に、表面部断面を同じく光学電子顕微鏡（２０００倍）を用いて観察し、異方性ＷＣ相の基体表面からの存在深さ（表面靭性層の深さ）を測定したところ、表１、２に示される結果を示した。
【０００９】
ついで、これらの超硬基体を、所定の形状に加工およびホーニング加工した状態で、その表面に、通常の化学蒸着装置を用い、表３に示される条件（表中、ｌ−ＴｉＣＮは縦長成長結晶組織を有するＴｉＣＮ層の形成条件を示し、これによって形成されたｌ−ＴｉＣＮ層は特開平６−８０１０号公報に記載されるものと同種の組織をもつものであり、またαＡｌ2Ｏ3およびκＡｌ2Ｏ3はそれぞれα型結晶構造およびκ型結晶構造を有するＡｌ2Ｏ3層の形成条件を示すものである）にて、表４、５に示される目標組成および目標層厚（切刃の逃げ面）の硬質被覆層を形成することにより、基体表面部に表面靭性層の存在する本発明被覆超硬工具１〜７および前記表面靭性層の形成がない従来被覆超硬工具１〜７をそれぞれ製造した。
【００１０】
つぎに、上記本発明被覆超硬工具１〜７および従来被覆超硬工具１〜７について、
被削材：ＪＩＳ・ＳＮＣＭ４４０の長さ方向等間隔４本縦溝入り丸棒、
切削速度：１８０ｍ／ｍｉｎ．、
切り込み：３ｍｍ、
送り：０．１５ｍｍ／ｒｅｖ．、
切削時間：２分、
の条件での合金鋼の乾式断続高切り込み切削試験、並びに、
被削材：ＪＩＳ・ＳＣｒ４２０Ｈの長さ方向等間隔４本縦溝入り丸棒、
切削速度：２００ｍ／ｍｉｎ．、
切り込み：１．５ｍｍ、
送り：０．３５ｍｍ／ｒｅｖ．、
切削時間：５分、
の条件での合金鋼の乾式断続高送り切削試験を行い、いずれの切削試験でも切刃の最大逃げ面摩耗幅を測定した。この測定結果を表６に示した。
【００１１】
【表１】
【表２】
【表３】
【表４】
【表５】
【表６】
【発明の効果】
表１〜６に示される結果から、基体表面部に偏平状（異方性）ＷＣ相が存在する表面靭性層を形成してなる本発明被覆超硬工具１〜７は、いずれも前記表面靭性層の形成によってすぐれた耐欠損性を具備するようになることから、特に一段と苛酷な条件である、断続切削を乾式で、かつ高送りおよび高切り込みの重切削条件で行っても切刃に欠けの発生なく、すぐれた耐摩耗性を長期に亘って発揮するのに対して、超硬基体の表面部に前記表面靭性層の形成がない従来被覆超硬工具１〜７においては、いずれも超硬基体の靭性不足が原因で高衝撃の加わる断続重切削では切刃に欠けが発生し、これが原因で比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆超硬工具は、例えば鋼や鋳鉄などの連続切削や断続切削は勿論のこと、特に高衝撃の加わる断続重切削にもすぐれた耐欠損性を発揮し、長期に亘ってすぐれた切削性能を示すものであるから、切削加工の省力化および省エネ化、さらに低コスト化に十分満足に対応できるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention is a surface-coated tungsten carbide-based cemented carbide cutting tool (hereinafter referred to as coated super-hard alloy) that exhibits excellent fracture resistance, particularly when intermittent cutting of steel or the like is performed under heavy cutting conditions such as high feed and high cutting. And a manufacturing method of the hard tool).
[0002]
[Prior art]
Conventionally, generally tungsten carbide based on an isotropic crystal growth phase (indicated by WC): 85 to 95% by weight, and the balance is a tungsten carbide superstructure having a composition composed of a Co-based binder phase and inevitable impurities. On the surface of a hard alloy substrate (hereinafter referred to as a cemented carbide substrate), a titanium carbide (hereinafter referred to as TiC) layer, a titanium nitride (hereinafter also referred to as TiN) layer, a titanium carbonitride (hereinafter referred to as TiCN) layer, Ti compound layer composed of one single layer or two or more types of titanium carbonate (hereinafter referred to as TiCO) layer and titanium carbonitride oxide (hereinafter referred to as TiCNO) layer, or the Ti compound There is known a coated carbide tool formed by chemical vapor deposition and / or physical vapor deposition of a hard coating layer composed of a layer and an aluminum oxide (hereinafter referred to as Al 2 O 3 ) layer with an average layer thickness of 4 to 15 μm. And This coated carbide tool is mainly used for continuous cutting and intermittent cutting of steel and the like.
In general, as the Al 2 O 3 layer constituting the hard coating layer of the above-mentioned coated carbide tool, those having an α-type crystal structure and those having a κ-type crystal structure are widely used in practical use, and the TiCN layer In addition to those having a granular crystal structure, for example, as described in JP-A-6-8010 and JP-A-7-328808, an organic carbonitride is used as a reaction gas in a normal chemical vapor deposition apparatus. There is also known one having a vertically elongated crystal structure by chemical vapor deposition in a medium temperature range of 700 to 950 ° C. using a mixed gas containing.
[0003]
[Problems to be solved by the invention]
On the other hand, there is a strong demand for labor saving and energy saving and cost reduction for cutting in recent years. With this, cutting tends to be performed under heavy cutting conditions such as high feed and high cutting. In conventional coated carbide tools, especially when this is used to perform intermittent cutting under heavy cutting conditions such as high feed and high cutting, the cutting edge tends to chip, which causes a relatively short service life. Is the current situation.
[0004]
[Means for Solving the Problems]
Therefore, the present inventors conducted research to improve the fracture resistance of the above-mentioned conventional coated carbide tool from the above viewpoint,
The cemented carbide substrate constituting the above conventional coated cemented carbide tool, that is, the cemented carbide substrate composed of an isotropic WC phase, is usually a green compact that is press-molded from a mixed powder of a predetermined composition. Is heated to a temperature of 1300 to 1500 ° C. in a vacuum atmosphere of 10 −2 to 10 −6 Torr, for example, and maintained at this temperature rising temperature for 1 to 3 hours and then sintered under furnace cooling conditions. However, at the time of raising the temperature in the sintering process of the conventional cemented carbide substrate, when the temperature is raised to 800 to 1200 ° C., first, the partial pressure of H 2 and CO 2 is changed from vacuum to 1 to 2 respectively. After the decarburization atmosphere was set to 20 Torr and kept in this decarburization atmosphere for a predetermined time, the temperature was kept at 800 to 1200 ° C., and the partial pressure of each atmosphere was H 2 : 1 to 20 Torr, CH 4 : 1~20Torr of H 2 and C And carburizing atmosphere consisting 4 mixed gas, the decarburization-carburization for a predetermined time to the carburizing atmosphere subjecting (provided that the decarburization-carburizing after heating to the sintering temperature, at the sintering temperature The holding and furnace cooling atmosphere is performed in a vacuum atmosphere as described above), and the [001] plane of the hexagonal crystal structure of WC is preferential in the surface portion of the cemented carbide substrate after sintering. A surface layer in which an anisotropic WC phase having a flattened shape is present is formed, and the flattened WC phase is compared with an isotropic (granular) WC phase. Since the bonding interface with the binder phase is increased, the surface layer on which the anisotropic (flat) WC phase is present has improved toughness, and in this case, the decarburization / carburization temperature is adjusted. The surface of the substrate is observed with an optical microscope, and the anisotropic WC phase is combined with the isotropic WC phase. And the decarburization and carburizing time is adjusted in the range of 10 to 30 minutes, respectively, so that the anisotropic WC phase has a depth of 50 to 500 μm from the substrate surface. If it exists over the entire length, the surface layer formed on the surface portion of the resulting cemented carbide substrate has extremely high toughness, and thus the above hard coating layer is formed on the surface layer. The coated carbide tool obtained the research result that the cutting edge does not have a chip even when it is used for intermittent heavy cutting of steel requiring high toughness and the cutting performance is exhibited over a long period of time.
[0005]
This invention was made based on the above research results,
(A) WC phase : 85 to 95% by weight, and the rest of the carbide substrate having a composition composed of a binder phase mainly composed of Co and inevitable impurities, a TiC layer, a TiN layer, a TiCN layer, a TiCO layer 4 to 15 μm of a Ti coating layer composed of a single layer or two or more layers of TiNO layer and TiCNO layer, or a Ti compound layer and an Al 2 O 3 layer. In the sintering step in a vacuum atmosphere of 10 −2 to 10 −6 Torr of the cemented carbide substrate constituting the coated carbide tool formed by chemical vapor deposition with an average layer thickness of
(B) When raising the temperature to a predetermined sintering temperature within the range of 1300 to 1500 ° C., first, when the temperature is raised to a predetermined temperature within the range of 800 to 1200 ° C., the atmosphere is changed from the vacuum to the respective minutes. A decarburization atmosphere consisting of a mixed gas of H 2 and CO 2 with a pressure of H 2 : 1 to 20 Torr and CO 2 : 1 to 20 Torr was maintained in this decarburization atmosphere for a predetermined time, and the temperature was similarly 800 to 1200 ° C. While maintaining a predetermined temperature within the range, the atmosphere is changed to a carburizing atmosphere consisting of a mixed gas of H 2 and CH 4 with partial pressures of H 2 : 1 to 20 Torr and CH 4 : 1 to 20 Torr. By performing decarburization and carburizing treatment that keeps the atmosphere for a predetermined time,
(C) An anisotropic WC having a shape in which the [001] plane of the hexagonal crystal structure of WC is preferentially grown and flattened by observing the surface of the substrate with an optical microscope on the surface of the cemented carbide substrate. The phase is present in a proportion of 20 to 60% by area in the WC phase, the rest shows a structure composed of the isotropic WC phase, and the anisotropic WC phase extends from the surface to a depth of 50 to 500 μm. Formed by forming an existing surface toughness layer,
It is characterized by a method of manufacturing a coated carbide tool that exhibits excellent fracture resistance in intermittent heavy cutting.
[0006]
In the coated carbide tool of the present invention, the proportion of the anisotropic WC phase on the substrate surface of the surface toughness layer formed on the surface portion of the carbide substrate constituting the same is 20-60 areas in the proportion of the WC phase. If the ratio is less than 20 area%, the desired toughness cannot be secured on the surface portion of the substrate. On the other hand, if the ratio exceeds 60 area%, the toughness is further improved. In particular, in dry intermittent heavy cutting where remarkably heat is generated, uneven wear occurs on the cutting edge, which leads to a service life, and the ratio is determined to be 20 to 60 area%, preferably 25 to 50%.
Further, the depth of the surface toughness layer from the substrate surface is set to 50 to 500 μm for the same reason. If the depth is less than 50 μm, the desired toughness cannot be ensured in the substrate surface portion. When the depth exceeds 500 μm, the cutting edge is likely to be thermoplastically deformed to reach the service life, and is preferably 100 to 300 μm.
[0007]
Furthermore, the ratio of the WC phase in the cemented carbide substrate constituting the coated carbide tool of the present invention is set to 85 to 95% by weight. When the ratio is less than 85% by weight, the ratio of the binder phase is relatively large. This is because the wear resistance of the substrate itself suddenly decreases, while if the ratio exceeds 95% by weight, the ratio of the binder phase decreases and the strength decreases. It is.
Further, the average thickness of the hard coating layer is set to 4 to 15 μm. If the average layer thickness is less than 4 μm, the desired wear resistance cannot be ensured, whereas if the average layer thickness exceeds 15 μm. This is because chipping and chipping are likely to occur in the cutting blade.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the coated carbide tool of the present invention will be specifically described with reference to examples.
As raw material powders, WC powder having an average particle diameter of 3 μm, Cr 3 C 2 powder of 1 μm, and Co powder of 3 μm were prepared. These raw material powders were blended in the blending composition shown in Table 1, and 72 in a ball mill. After wet-mixing for a period of time and drying, this mixed powder is press-molded into a green compact in the form of a throwaway tip conforming to ISO standard CNMG120408, and these green compacts are placed in a vacuum atmosphere of 10 −3 torr in a vacuum atmosphere of 800-3. when the temperature was raised to a predetermined temperature in the range of 1200 ° C., firstly, the atmosphere, H 2 from the vacuum: 10 Torr, CO 2: 10 Torr decarburizing atmosphere consisting of the partial pressure of the mixed gas of H 2 and CO 2 After maintaining in this decarburizing atmosphere for 20 minutes, the temperature is maintained at a predetermined temperature in the range of 800 to 1200 ° C., and the partial pressure of each atmosphere is H 2 : 10 Torr. , CH 4 : Carburized atmosphere consisting of a mixed gas of H 2 and CH 4 of 10 Torr, decarburized and carburized for 20 minutes, and then the atmosphere is changed to a vacuum atmosphere of 10 −3 torr. The temperature is raised to a predetermined temperature within a range of 1400 to 1460 ° C., and thereafter the above-mentioned vacuum atmosphere is maintained, the temperature is maintained at this temperature increase for 1 hour, and the substrate is cooled by furnace to cool the carbide substrates A to G, respectively. Manufactured.
Furthermore, for the purpose of comparison, as shown in Table 2, the decarburization / carburization treatment in the temperature raising process in the production of the above-mentioned carbide substrates A to G is not performed, and the temperature rise to the sintering temperature is Carbide substrates a to g were respectively produced under the same conditions except that they were performed in a vacuum atmosphere of 10 −3 torr.
The surface of each of the above-mentioned superhard substrates A to G and superhard substrates a to g is observed with an optical electron microscope (5000 times), and the total proportion of the WC phase and the anisotropic WC phase in the WC phase and The ratio of the isotropic WC phase is measured using an image analyzer, and the cross section of the surface is also observed using an optical electron microscope (2000 times), and the depth of the anisotropic WC phase from the substrate surface ( When the depth of the surface toughness layer was measured, the results shown in Tables 1 and 2 were shown.
[0009]
Next, these carbide substrates were processed and honed into a predetermined shape, and the surface thereof was subjected to the conditions shown in Table 3 using a normal chemical vapor deposition apparatus (in the table, l-TiCN is a vertically grown crystal). The formation conditions of a TiCN layer having a structure are shown, and the 1-TiCN layer formed thereby has the same kind of structure as described in JP-A-6-8010, and αAl 2 O 3 and κAl 2 O 3 indicates the formation conditions of an Al 2 O 3 layer having an α-type crystal structure and a κ-type crystal structure, respectively, and the target composition and target layer thickness (of the cutting edge) shown in Tables 4 and 5 By forming a hard coating layer of the flank), the coated carbide tools 1 to 7 of the present invention in which a surface toughness layer is present on the surface of the substrate and the conventional coated carbide tools 1 to 7 having no surface toughness layer are formed. Each was manufactured.
[0010]
Next, for the present invention coated carbide tools 1-7 and conventional coated carbide tools 1-7,
Work material: JIS / SNCM440 lengthwise equidistant 4 round bars with vertical grooves,
Cutting speed: 180 m / min. ,
Incision: 3mm,
Feed: 0.15 mm / rev. ,
Cutting time: 2 minutes
Dry intermittent high cutting test of alloy steel under the conditions of, and
Work material: JIS · SCr420H lengthwise equidistant 4 round bars with vertical grooves,
Cutting speed: 200 m / min. ,
Incision: 1.5mm,
Feed: 0.35 mm / rev. ,
Cutting time: 5 minutes
The dry intermittent high feed cutting test of the alloy steel was performed under the above conditions, and the maximum flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.
[0011]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
[Table 6]
【The invention's effect】
From the results shown in Tables 1 to 6, the coated tough tools 1 to 7 of the present invention formed by forming a surface toughness layer having a flat (anisotropic) WC phase on the surface of the substrate are all the surface toughness. Since the formation of a layer provides excellent fracture resistance, the cutting edge is chipped even when interrupted cutting is performed under dry conditions, with high feed and high cutting conditions, which is a particularly severe condition. In the conventional coated cemented carbide tools 1 to 7 where the surface toughness layer is not formed on the surface portion of the cemented carbide substrate, excellent wear resistance is exhibited over a long period of time. It is clear that intermittent cutting with high impact due to insufficient toughness of the hard substrate causes chipping on the cutting edge, which leads to a service life in a relatively short time.
As described above, the coated cemented carbide tool of the present invention exhibits excellent fracture resistance not only for continuous cutting and intermittent cutting of, for example, steel and cast iron, but particularly for intermittent heavy cutting with high impact, and for a long time. Since the cutting performance is excellent over a long period of time, it is possible to satisfactorily cope with labor saving, energy saving, and cost reduction in cutting.
Claims (1)
（ｂ）１３００〜１５００℃の範囲内の所定の焼結温度への昇温に際して、まず、８００〜１２００℃の範囲内の所定の温度に昇温した時点で、その雰囲気を真空からそれぞれの分圧がＨ ２ ：１〜２０Ｔｏｒｒ、ＣＯ ２ ：１〜２０ＴｏｒｒのＨ ２ とＣＯ ２ の混合ガスからなる脱炭雰囲気とし、この脱炭雰囲気に所定時間保持した後、温度は同じく８００〜１２００℃の範囲内の所定の温度に保持したままで、その雰囲気をそれぞれの分圧がＨ ２ ：１〜２０Ｔｏｒｒ、ＣＨ ４ ：１〜２０ＴｏｒｒのＨ ２ とＣＨ ４ の混合ガスからなる浸炭雰囲気とし、この浸炭雰囲気に所定時間保持する脱炭・浸炭処理を施すことにより、
（ｃ）上記炭化タングステン基超硬合金基体の表面部に、前記基体表面を光学顕微鏡で観察して、炭化タングステンのもつ六方晶結晶構造の[００１]面が優先的に成長して偏平化した形状の異方性炭化タングステン相が炭化タングステン相に占める割合で２０〜６０面積％存在し、残りが上記等方性の炭化タングステン相からなる組織を示し、かつ前記異方性炭化タングステン相が表面から５０〜５００μｍの深さに亘って存在する表面靭性層を形成すること、
を特徴とする断続重切削ですぐれた耐欠損性を発揮する表面被覆炭化タングステン基超硬合金製切削工具の製造方法。(A) Tungsten carbide phase : 85 to 95% by weight, and the remainder of the tungsten carbide base cemented carbide substrate having a composition consisting of a binder phase mainly composed of Co and inevitable impurities, a titanium carbide layer, titanium nitride A Ti compound layer composed of one single layer or two or more multilayers of a layer, a titanium carbonitride layer, a carbonated titanium carbonate layer, and a titanium carbonitride oxide layer, or the Ti compound layer and the aluminum oxide layer. 10 −2 to 10 −6 Torr of the tungsten carbide-based cemented carbide substrate constituting the surface-coated tungsten carbide-based cemented carbide cutting tool formed by chemical vapor deposition of the hard coating layer having an average thickness of 4 to 15 μm In the sintering process in a vacuum atmosphere of
(B) When raising the temperature to a predetermined sintering temperature within the range of 1300 to 1500 ° C., first, when the temperature is raised to a predetermined temperature within the range of 800 to 1200 ° C., the atmosphere is changed from the vacuum to the respective minutes. A decarburization atmosphere consisting of a mixed gas of H 2 and CO 2 with a pressure of H 2 : 1 to 20 Torr and CO 2 : 1 to 20 Torr was maintained in this decarburization atmosphere for a predetermined time, and the temperature was similarly 800 to 1200 ° C. While maintaining a predetermined temperature within the range, the atmosphere is changed to a carburizing atmosphere consisting of a mixed gas of H 2 and CH 4 with partial pressures of H 2 : 1 to 20 Torr and CH 4 : 1 to 20 Torr. By performing decarburization and carburizing treatment that keeps the atmosphere for a predetermined time,
(C) The surface of the substrate was observed with an optical microscope on the surface portion of the tungsten carbide base cemented carbide substrate, and the [001] plane of the hexagonal crystal structure of tungsten carbide was preferentially grown and flattened. The proportion of the anisotropic tungsten carbide phase in the shape is 20 to 60% by area in the tungsten carbide phase, and the rest shows a structure composed of the isotropic tungsten carbide phase, and the anisotropic tungsten carbide phase is the surface. Forming a surface toughness layer existing over a depth of 50 to 500 μm,
A method for producing a surface-coated tungsten carbide-based cemented carbide cutting tool exhibiting excellent fracture resistance in intermittent heavy cutting characterized by
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| CN102732766A (en) * | 2012-07-06 | 2012-10-17 | 四川大学 | Coarse grain hard alloy material and preparation method thereof |
| CN110691663A (en) * | 2018-03-19 | 2020-01-14 | 住友电气工业株式会社 | Surface-coated cutting tool |
| CN110709198A (en) * | 2018-03-19 | 2020-01-17 | 住友电气工业株式会社 | Surface-coated cutting tool |
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| US20200171582A1 (en) * | 2018-03-19 | 2020-06-04 | Sumitomo Electric Industries, Ltd. | Surface-coated cutting tool |
| CN109371306A (en) * | 2018-12-15 | 2019-02-22 | 宇龙精机科技（浙江）有限公司 | A kind of lathe of five-axle linkage processing |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102732766A (en) * | 2012-07-06 | 2012-10-17 | 四川大学 | Coarse grain hard alloy material and preparation method thereof |
| CN102732766B (en) * | 2012-07-06 | 2014-08-06 | 四川大学 | Coarse grain hard alloy material and preparation method thereof |
| CN110691663A (en) * | 2018-03-19 | 2020-01-14 | 住友电气工业株式会社 | Surface-coated cutting tool |
| CN110709198A (en) * | 2018-03-19 | 2020-01-17 | 住友电气工业株式会社 | Surface-coated cutting tool |
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