JP3972775B2

JP3972775B2 - A surface-coated cemented carbide drill that exhibits excellent heat-resistant plastic deformation in high-speed drilling.

Info

Publication number: JP3972775B2
Application number: JP2002262983A
Authority: JP
Inventors: 一樹岡田; 慧高橋; 俊之谷内
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2001-10-12
Filing date: 2002-09-09
Publication date: 2007-09-05
Anticipated expiration: 2022-09-09
Also published as: JP2003181712A

Description

【０００１】
【発明の属する技術分野】
この発明は、特に超硬合金基体を構成する硬質相が強度の低下なく、すぐれた高温硬さと耐熱性を有し、したがって高熱発生を伴なう鋼や鋳鉄などの高速穴あけ切削加工で、すぐれた耐熱塑性変形性を発揮する表面被覆超硬合金製ドリル（以下、被覆超硬ドリルと云う）に関するものである。
【０００２】
【従来の技術】
従来、一般に、鋼や鋳鉄などの被削材の穴あけ切削加工などに、例えば図１（ａ）に概略拡大正面図で、同（ｂ）に溝形成部の概略横断面図で示される形状を有する各種の超硬合金製ドリル（以下、超硬ドリルと云う）が用いられている。
また、切削性能の一段の向上を目的として、超硬ドリルを基体とし、この基体の表面に、
組成式：［Ｔｉ_1-XＡｌ_X］Ｎで表わした場合、厚さ方向中央部のオージェ分光分析装置による測定で、原子比で、Ｘ：０．３〜０．７を満足するＴｉとＡｌの複合窒化物［以下、（Ｔｉ，Ａｌ）Ｎで示す］層で構成された硬質被覆層を０．５〜６μｍの平均層厚で物理蒸着してなる被覆超硬ドリルも知られている（例えば、特許文献２参照）。
上記の超硬ドリルの少なくとも溝形成部が、実質的に結合相と硬質相で構成され、結合相形成成分として質量％（以下、％は質量％を示す）で、６〜１６％の割合で含有するＣｏ中に０．１〜３％の割合で固溶含有したＣｒおよび／またはＶ成分による粒成長抑制作用で、硬質相を構成する炭化タングステン（以下、ＷＣで示す）の粒径を、平均粒径で、望ましくは０．７μｍ以下とした微粒組織の超硬合金からなることも知られている（例えば、特許文献１参照）。
さらに、上記の超硬ドリルが、例えば原料粉末として、いずれも０．１〜３μｍの範囲内の所定の平均粒径を有するＷＣ粉末、炭化クロム（以下、Ｃｒ₃Ｃ₂で示す）粉末、炭化バナジウム（以下、ＶＣで示す）粉末、およびＣｏ粉末を用い、これら原料粉末を所定の配合組成に配合し、湿式混合し、乾燥した後、押出しプレスにて所定の直径の長尺状成形体とし、この長尺状成形体を、１．３〜１３．３Ｐａの真空雰囲気中、１３５０〜１４８０℃の範囲内の所定の温度に昇温し、この昇温温度に１〜２時間保持後、雰囲気を、例えばＡｒを導入して４．９〜１４．７ＭＰａの加圧雰囲気とし、前記昇温温度および加圧雰囲気の条件下に１５〜６０分間保持した後、少なくとも１２００℃までを５０〜１００℃／ｍｉｎの冷却速度で冷却して、Ｃｒ（Ｃｒ₃Ｃ₂）および／またはＶ（ＶＣ）がＣｏ中に固溶してなる結合相とＷＣの硬質相で構成された超硬合金からなる所定の直径の長尺状加圧焼結体を形成し、この加圧焼結体から図１に例示される形状に研削加工することにより製造されることも知られている（例えば、特許文献１参照）。
また、さらに上記の被覆超硬ドリルが、超硬ドリルを基体とし、この基体を、例えば図２に概略説明図で示される物理蒸着装置の１種であるアークイオンプレーティング装置に装入し、ヒータで装置内を、例えば雰囲気を１．３×１０^{- 3}Ｐａの真空として、５００℃の温度に加熱した状態で、アノード電極と所定組成を有するＴｉ−Ａｌ合金がセットされたカソード電極（蒸発源）との間に、例えば電圧：３５Ｖ、電流：９０Ａの条件でアーク放電を発生させ、同時に装置内に反応ガスとして窒素ガスを導入し、一方前記基体には、例えば−２００Ｖのバイアス電圧を印加した条件で、前記基体の表面に、上記の（Ｔｉ，Ａｌ）Ｎからなる硬質被覆層を物理蒸着することにより製造されることも知られている（例えば、特許文献２参照）。
【０００３】
【特許文献１】
特開昭６１−１２８４７号公報
【特許文献２】
特開平８−２０９３３号公報
【０００４】
【発明が解決しようとする課題】
一方、近年の切削加工の省力化および省エネ化、さらに低コスト化に対する要求は強く、これに伴い、切削装置の高性能化と相俟って、切削加工は高速で行われる傾向にあるが、上記の従来被覆超硬ドリルにおいては、これを高速穴あけ切削加工に用いると、特に超硬合金基体の高温硬さおよび耐熱性不足が原因で、先端部の切刃面に偏摩耗の原因となる熱塑性変形が発生し易くなり、この結果摩耗進行が促進されるようになることから、比較的短時間で使用寿命に至るのが現状である。
【０００５】
【課題を解決するための手段】
そこで、本発明者らは、上述のような観点から、高速穴あけ切削加工で、すぐれた耐熱塑性変形性を発揮する被覆超硬ドリルを開発すべく、特に上記の従来被覆超硬ドリルに着目し、研究を行った結果、
（ａ）通常、従来の原料粉末としてのＷＣ粉末は、高純度を意図して製造されているため、焼結後の超硬合金基体の硬質相を構成するＷＣの不純物である窒素および酸素の含有量は、前記硬質相の中心部をオージェ電子分光分析装置を用いて測定した値で、
酸素（Ｏ）：０．００１〜０．０５％、
窒素（Ｎ）：０．００１〜０．０３％、
であるのが一般的であること。
【０００６】
（ｂ）一般に、上記の従来高純度ＷＣ粉末は、原料粉末としてＷＯ₃粉末を用い、これに還元粉末として所定量のカーボンブラックを配合し、混合した後、この混合粉末を９５０〜１０５０℃に加熱し、窒素気流中で所定時間保持の条件で還元処理を行い、ついで加熱温度を１１５０〜１２５０℃とすると共に、前記窒素気流を水素気流に変えて所定時間保持の条件で炭化処理を行うことにより製造されているが、この従来高純度ＷＣ粉末の製造において、還元処理の窒素気流中および炭化処理の水素気流中に所定割合、望ましくは５〜１５容量％の割合でＣＯガスを配合すると、製造されたＷＣ粉末中の酸素含有量および窒素含有量が上昇するようになり、前記のＣＯガスの５〜１５容量％の配合で、製造されたＷＣ粉末は、
酸素（Ｏ）：０．２〜０．６％、
窒素（Ｎ）：０．１〜０．２５％、
を含有するようになること。
【０００７】
（ｃ）この結果の高酸素高窒素含有のＷＣ粉末を原料粉末として用いて製造された超硬合金基体においては、これの硬質相は、その中心部をオージェ電子分光分析装置を用いて測定した値で、前記高酸素高窒素含有のＷＣ粉末と同じＯ：０．２〜０．６％、Ｎ：０．１〜０．２５％、の含有量を示し、この結果前記含有量のＯによってすぐれた高温硬さと耐熱性を具備し、一方前記Ｏ含有によって硬質相の強度は低下するようになるが、このＯ含有による強度低下を前記含有量のＮによって抑制することから、高純度硬質相と同等の高強度が保持され、したがってこの超硬合金基体で構成された被覆超硬ドリルは、高熱発生を伴なう高速穴あけ切削加工でもすぐれた耐熱塑性変形性を発揮し、長期に亘ってすぐれた耐摩耗性を示すこと。
以上（ａ）〜（ｃ）に示される研究結果を得たのである。
【０００８】
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、溝形成部とシャンク部からなり、少なくとも前記溝形成部が、実質的に結合相と硬質相で構成された超硬合金からなる基体の表面に、０．５〜６μｍの平均層厚で、
組成式：［Ｔｉ_1-XＡｌ_X］Ｎで表わした場合、厚さ方向中央部のオージェ分光分析装置による測定で、原子比で、Ｘ：０．３〜０．７を満足する（Ｔｉ，Ａｌ）Ｎからなる硬質被覆層を物理蒸着してなる被覆超硬ドリルにおいて、
上記超硬合金基体を、いずれも結合相形成成分として、
Ｃｏ：６〜１６％、
Ｃｒおよび／またはＶ：０．１〜３％、
を含有し、残りの硬質相が酸素（Ｏ）および窒素（Ｎ）を固溶含有するＷＣからなる組成を有し、かつ前記硬質相のＯおよびＮ含有量が、前記硬質相の中心部をオージェ電子分光分析装置を用いて測定した値で、
Ｏ：０．２〜０．６％、
Ｎ：０．１〜０．２５％、
である超硬合金で構成してなる、高速穴あけ切削加工ですぐれた耐熱塑性変形性を発揮する被覆超硬ドリルに特徴を有するものである。
【０００９】
以下に、この発明の被覆超硬ドリルにおいて、これを構成する超硬合金基体の組成、および硬質被覆層の平均層厚を上記の通りに限定した理由を説明する。
（１）超硬合金基体のＣｏ含有量
結合相形成成分としてのＣｏ含有量が６％未満では基体に所望の強度および靭性を確保することができず、一方Ｃｏ含有量が１６％を超えると熱塑性変形を起し易くなり、偏摩耗の進行が促進するようになることから、Ｃｏ含有量を６〜１６％と定めた。
【００１０】
（２）超硬合金基体のＣｒおよび／またはＶ
これらの成分には、結合相を形成するＣｏ中に固溶した状態で硬質相の成長を著しく抑制して、これの粒径を平均粒径で、望ましくは０．７μｍ以下とした微粒組織とする作用があるが、この作用はＣｒおよびＶ成分の含有量が０．１％未満では不充分となり、一方その含有量が３％を超えると、これらの成分が炭化物として析出し、強度および靭性を低下させるようになることから、その含有量を０．１〜３％と定めた。
【００１１】
（３）超硬合金基体の硬質相のＯ含有量
超硬合金基体の硬質相におけるＯ含有量が０．２％未満では、所望のすぐれた高温硬さと耐熱性を確保することができないので、前記硬質相を構成するＷＣ粉末の製造時に、還元処理の窒素気流中および炭化処理の水素気流中に配合するＣＯガスの割合を調整して０．２％以上含有させ、すぐれた高温硬さと耐熱性を確保して、高熱発生の高速穴あけ切削加工でもすぐれた耐熱塑性変形性を発揮するようにするが、一方その含有量が０．６％を超えるとＮ含有によっても硬質相自体の強度低下を阻止することができず、この結果先端切刃面にチッピング（微小欠け）が発生し易くなり、使用寿命短命化をもたらすことから、その含有量を０．２〜０．６％と定めた。
【００１２】
（４）超硬合金基体の硬質相のＮ含有量
また、Ｎ含有量が０．１％未満では、上記のＯ含有による強度低下を完全に阻止することができないので、原料粉末として用いられるＷＣ粉末の製造に際して、還元処理の窒素気流中および炭化処理の水素気流中に配合するＣＯガスの割合を調整して０．１％以上含有するようにするが、一方その含有量が０．２５％を超えると上記のＯ含有によってもたらされる高温硬さと耐熱性の向上効果が低下し、所望の高温硬さと耐熱性を確保することができなくなり、摩耗進行が著しく促進され、使用寿命短命化の原因となることから、その含有量を０．１〜０．２５％と定めた。
【００１３】
（５）硬質被覆層の組成式
硬質被覆層を構成する（Ｔｉ，Ａｌ）ＮにおけるＡｌはＴｉＮに対して高温硬さおよび耐熱性を高め、もって耐摩耗性を向上させるために固溶するものであり、したがって組成式：（Ｔｉ_1-XＡｌ_X）ＮのＸ値が原子比（以下同じ）で、０．３未満では所望の耐摩耗性を確保することができず、一方その値が０．７を越えると、先端切刃面に欠けやチッピングが発生し易くなると云う理由によりＸ値を０．３〜０．７と定めた。
【００１４】
（６）硬質被覆層の平均層厚
その平均層厚が０．５μｍ未満では硬質被覆層によってもたらされるすぐれた耐摩耗性を確保することができず、一方その平均層厚が６μｍを超えると硬質被覆層にチッピングが発生し易くなることから、その平均層厚を０．５〜６μｍと定めた。
【００１５】
【発明の実施の態様】
つぎに、この発明の被覆超硬ドリル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：０．５μｍを有するＷＯ₃粉末、および同０．２μｍのカーボンブラックを用意し、まずこれら原料粉末を、カーボンブラック：１７％、ＷＯ₃粉末：残り、の割合に配合し、湿式ボールミルでアセトンを加えて３時間混合し、減圧乾燥した後、よくほぐした状態でカーボンボートに充填した後、この混合粉末を９５０〜１０５０℃に加熱し、ＣＯガスを５〜１５容量％の範囲内の所定の割合で配合してなる窒素−ＣＯ混合気流中で３時間保持の条件で還元処理を行い、ついで加熱温度を１１５０〜１２５０℃とすると共に、前記窒素−ＣＯ混合気流を同じくＣＯガスを５〜１５容量％の範囲内の所定の割合で配合してなる水素−ＣＯ混合気流に変えて３時間保持の条件で炭化処理を行い、最終的に粒度調整を行うことにより、表１に示される窒素および酸素を含有し、かつ平均粒径をもった本発明被覆超硬ドリルの超硬合金基体製造用原料粉末としてのＷＣ粉末（以下、本発明原料ＷＣ粉末という）ａ−１〜ａ−７をそれぞれ製造した。
【００１６】
また、比較の目的で、還元処理の反応雰囲気を窒素気流、炭化処理の反応雰囲気を水素気流とする以外は、同一の条件で、同じく表１に示される窒素および酸素含有量、並びに平均粒径の従来被覆超硬ドリルの超硬合金基体製造用原料粉末としてのＷＣ粉末（以下、従来原料ＷＣ粉末という）ｂ−１〜ｂ−７をそれぞれ製造した。
【００１７】
ついで、上記の本発明原料ＷＣ粉末ａ−１〜ａ−７および従来原料ＷＣ粉末ｂ−１〜ｂ−７のそれぞれに、平均粒径：１．２μｍのＣｏ粉末、同１．８μｍのＶＣ粉末、および同２．３μｍのＣｒ₃Ｃ₂粉末を表２に示される割合に配合し、ボールミルで７２時間湿式混合し、減圧乾燥し、さらにワックスと溶剤を加えて１時間混和した後、押出しプレスにて４〜２６ｍｍの範囲内の所定の直径を有する長尺状成形体を形成し、これらの長尺状成形体を、１．３Ｐａの真空雰囲気中、１３８０〜１４８０℃の範囲内の所定の温度に１時間保持して焼結した後、前記昇温温度に保持したまま、Ａｒを導入して雰囲気を圧力：６ＭＰａの加圧雰囲気として１時間保持し、その後冷却のＨＩＰ処理を施すことにより、３．３〜２１．０ｍｍの範囲内の所定の直径を有する長尺状加圧焼結体とし、さらにこれらの加圧焼結体から研削加工にて、溝形成部の外径をそれぞれ表２に示される寸法とした本発明超硬合金基体Ａ−１〜Ａ−７および従来超硬合金基体Ｂ−１〜Ｂ−７をそれぞれを製造した。
【００１８】
ついで、これら超硬合金基体を、アセトン中で超音波洗浄し、乾燥した状態で、それぞれ図２に例示される通常のアークイオンプレーティング装置に装入し、一方カソード電極（蒸発源）として、それぞれ種々の成分組成をもったＴｉ−Ａｌ合金を装着し、装置内を排気して０．５Ｐａの真空に保持しながら、ヒーターで装置内を５００℃に加熱した後、Ａｒガスを装置内に導入して１０ＰａのＡｒ雰囲気とし、この状態で前記超硬合金基体に−８００Ｖのバイアス電圧を印加して前記超硬合金基体表面をＡｒガスボンバート洗浄し、ついで装置内に反応ガスとして、窒素ガスを導入して６Ｐａの反応雰囲気とすると共に、前記超硬合金基体に印加するバイアス電圧を−２００Ｖに下げて、前記カソード電極とアノード電極との間にアーク放電を発生させ、もって前記超硬合金基体のそれぞれの表面に、表３に示される目標Ａｌ含有量および目標層厚の（Ｔｉ，Ａｌ）Ｎからなる硬質被覆層を蒸着することにより、本発明被覆超硬ドリル１〜７および従来被覆超硬ドリル１〜７をそれぞれ製造した。
【００１９】
この結果得られた本発明被覆超硬ドリル１〜７および従来被覆超硬ドリル１〜７について、オージェ電子分光分析装置を用い、これを構成する超硬合金基体における任意５個の硬質相の中心部のＯ含有量およびＮ含有量を測定し、この結果を表２に平均値で示した。
表２には、これらの被覆超硬ドリルを構成する超硬合金基体の任意断面における硬質相の平均粒径を走査型電子顕微鏡を用いて測定した結果も示した。
また、同じく上記超硬合金基体のＣｏ、Ｃｒ、およびＶの含有量を測定したところ、配合組成と実質的に同じ値を示した。
さらに、上記の本発明被覆超硬ドリル１〜７および従来被覆超硬ドリル１〜７を構成するそれぞれの硬質被覆層について、その厚さ断面中央部の組成をオージェ分光分析装置を用いて測定し、またその層厚を走査型電子顕微鏡を用いて測定したところ、いずれの場合も目標組成および目標層厚と実質的に同じ組成および層厚を示した。
【００２０】
つぎに、上記の各種の被覆超硬ドリルについて、被削材として、平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＳＣＭ４４０の合金鋼板材を用い、表３に示される条件で湿式高速穴あけ切削加工を行い、溝形成部の先端切刃面直上部における外径の縮径量が表３に示される値に達した時点を使用寿命とし、この使用寿命に至るまでの穴あけ加工数を測定した。これらの測定結果を表３にそれぞれ平均値で示した。
【００２１】
【表１】

【００２２】
【表２】

【００２３】
【表３】

【００２４】
【発明の効果】
表１〜３に示される結果から、本発明被覆超硬ドリル１〜７は、いずれもこれを構成する超硬合金基体の硬質相のＯおよびＮの含有量が相対的に高く、前記硬質相によってすぐれた高温硬さと耐熱性が確保されることから、高熱発生を伴なう高速穴あけ切削加工でも、特に先端部の切刃面部に偏摩耗の原因となる熱塑性変形の発生なく、正常摩耗を維持し、すぐれた耐摩耗性を発揮するのに対して、前記硬質相のＯおよびＮの含有量が相対的に低い従来被覆超硬ドリル１〜７においては、いずれも超硬合金基体の硬質相の高温硬さおよび耐熱性不足が原因で、高速穴あけ切削加工では前記切刃面部に熱塑性変形が起り易くなり、この結果摩耗は偏摩耗形態を採るようになることから、摩耗進行が著しく促進され、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ドリルは、通常の条件での穴あけ切削加工は勿論のこと、高速穴あけ切削加工でもすぐれた耐摩耗性を長期に亘って発揮するものであるから、穴あけ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することができるものである。
【図面の簡単な説明】
【図１】（ａ）は被覆超硬ドリルを例示する概略拡大正面図、（ｂ）は溝形成部の長さ方向中央部における中心線に対して直角な方向の概略断面図（概略横断面図）である。
【図２】アークイオンプレーティング装置の概略説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention is particularly advantageous in high-speed drilling of steel and cast iron with high heat generation because the hard phase constituting the cemented carbide base body has excellent strength and heat resistance without deterioration in strength. The present invention relates to a surface-coated cemented carbide drill (hereinafter referred to as a coated carbide drill) that exhibits excellent heat-resistant plastic deformation.
[0002]
[Prior art]
Conventionally, in general, for example, a drilling process of a work material such as steel or cast iron, for example, a schematic enlarged front view in FIG. 1A and a schematic cross-sectional view of a groove forming portion in FIG. Various types of cemented carbide drills (hereinafter referred to as cemented carbide drills) are used.
Also, for the purpose of further improving the cutting performance, a carbide drill is used as a base, and the surface of the base is
Compositional formula: [Ti _1-X Al _X ] N Ti and Al satisfying an atomic ratio of X: 0.3 to 0.7 as measured by an Auger spectrometer at the center in the thickness direction. There is also known a coated carbide drill formed by physically vapor-depositing a hard coating layer composed of a composite nitride (hereinafter referred to as (Ti, Al) N) layer with an average layer thickness of 0.5 to 6 μm ( For example, see Patent Document 2).
At least the groove forming part of the above-mentioned cemented carbide drill is substantially composed of a binder phase and a hard phase, and the binder phase forming component is in mass% (hereinafter,% indicates mass%), in a ratio of 6 to 16%. The particle size of tungsten carbide constituting the hard phase (hereinafter referred to as WC) by the grain growth suppressing action by Cr and / or V component contained in a solid solution at a ratio of 0.1 to 3% in the contained Co, It is also known that it is made of a cemented carbide having a fine grain structure with an average particle size of preferably 0.7 μm or less (see, for example, Patent Document 1).
Furthermore, the above carbide drills are, for example, WC powder, chromium carbide (hereinafter referred to as Cr ₃ C ₂ ) powder having a predetermined average particle diameter in the range of 0.1 to ₃ μm, carbonization as raw material powder, for example. Using vanadium (hereinafter referred to as VC) powder and Co powder, these raw material powders are blended into a predetermined blending composition, wet-mixed, dried, and then formed into a long shaped body with a predetermined diameter by an extrusion press. The long shaped body was heated to a predetermined temperature within a range of 1350 to 1480 ° C. in a vacuum atmosphere of 1.3 to 13.3 Pa, and kept at this temperature rising temperature for 1 to 2 hours. For example, Ar is introduced to form a pressurized atmosphere of 4.9 to 14.7 MPa, and the temperature is maintained for 15 to 60 minutes under the conditions of the temperature rise and the pressurized atmosphere, and then at least 1200 ° C. is 50 to 100 ° C. Cool at a cooling rate of / min , Cr (Cr ₃ C ₂ ) and / or V (VC) is a long pressurization with a predetermined diameter made of a cemented carbide composed of a binder phase in which Co is dissolved in Co and a hard phase of WC. It is also known that a bonded body is formed and manufactured by grinding the pressure sintered body into the shape illustrated in FIG. 1 (see, for example, Patent Document 1).
Further, the above-mentioned coated carbide drill has a carbide drill as a base, and the base is loaded into, for example, an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. A cathode electrode (evaporation) in which a Ti—Al alloy having a predetermined composition is set in a state where the inside of the apparatus is heated to a temperature of 500 ° C., for example, with a vacuum of 1.3 × 10 ⁻³ Pa in a heater. For example, arc discharge is generated under the conditions of a voltage of 35 V and a current of 90 A, and nitrogen gas is introduced as a reaction gas into the apparatus at the same time, while a bias voltage of −200 V is applied to the substrate, for example. It is also known that the hard coating layer made of the above (Ti, Al) N is physically vapor-deposited on the surface of the substrate under the applied conditions (for example, see Patent Document 2).
[0003]
[Patent Document 1]
JP 61-12847 [Patent Document 2]
JP-A-8-20933 gazette
[Problems to be solved by the invention]
On the other hand, there is a strong demand for labor saving and energy saving of cutting work and cost reduction in recent years, and along with this, cutting performance tends to be performed at a high speed in combination with high performance of cutting equipment. In the above-mentioned conventional coated carbide drill, if this is used for high-speed drilling, it causes uneven wear on the cutting edge surface of the tip, particularly due to the high temperature hardness and insufficient heat resistance of the cemented carbide substrate. Thermoplastic deformation is likely to occur, and as a result, the progress of wear is promoted, so that the service life is reached in a relatively short time.
[0005]
[Means for Solving the Problems]
In view of the above, the present inventors focused on the above-mentioned conventional coated carbide drill in order to develop a coated carbide drill that exhibits excellent heat-resistant plastic deformation by high-speed drilling. , As a result of research,
(A) Usually, WC powder as a conventional raw material powder is manufactured with the intention of high purity, so that nitrogen and oxygen, which are impurities of WC constituting the hard phase of the cemented carbide substrate after sintering, The content is a value obtained by measuring the central portion of the hard phase using an Auger electron spectroscopy analyzer,
Oxygen (O): 0.001 to 0.05%,
Nitrogen (N): 0.001 to 0.03%,
It is common to be.
[0006]
(B) In general, the above conventional high purity WC powder uses WO ₃ powder as a raw material powder, and a predetermined amount of carbon black as a reducing powder is mixed and mixed, and then the mixed powder is heated to 950 to 1050 ° C. Heating and performing a reduction treatment under a condition of holding in a nitrogen stream for a predetermined time, then setting the heating temperature to 1150 to 1250 ° C., and changing the nitrogen stream into a hydrogen stream and performing a carbonization treatment under a condition of holding for a predetermined time In the production of this conventional high-purity WC powder, when CO gas is blended in a predetermined ratio, preferably 5 to 15% by volume, in a nitrogen stream of reduction treatment and a hydrogen stream of carbonization treatment, Oxygen content and nitrogen content in the produced WC powder are increased, and the produced WC powder with a blend of 5 to 15% by volume of the CO gas is
Oxygen (O): 0.2-0.6%
Nitrogen (N): 0.1-0.25%,
To come to contain.
[0007]
(C) In the cemented carbide substrate manufactured using the high oxygen content and high nitrogen content WC powder as a raw material powder, the hard phase of the cemented carbide base was measured using an Auger electron spectrometer. In the value, the same O: 0.2-0.6%, N: 0.1-0.25% content as the high oxygen-high nitrogen content WC powder is shown. It has excellent high-temperature hardness and heat resistance. On the other hand, the strength of the hard phase decreases due to the inclusion of O, but since the decrease in strength due to the inclusion of O is suppressed by the N content, the high purity hard phase Therefore, the coated carbide drill composed of this cemented carbide substrate exhibits excellent heat-resistant plastic deformation even in high-speed drilling with high heat generation. Exhibit excellent wear resistance.
The research results shown in (a) to (c) above were obtained.
[0008]
The present invention has been made based on the above research results, and is composed of a cemented carbide composed of a groove forming portion and a shank portion, at least the groove forming portion being substantially composed of a binder phase and a hard phase. On the surface of the substrate with an average layer thickness of 0.5-6 μm,
When expressed by the composition formula: [Ti _1-X Al _X ] N, X: 0.3 to 0.7 is satisfied in terms of atomic ratio as measured by an Auger spectrometer at the center in the thickness direction (Ti, In a coated carbide drill formed by physical vapor deposition of a hard coating layer made of Al) N,
Any of the above cemented carbide substrates as a binder phase forming component,
Co: 6-16%
Cr and / or V: 0.1 to 3%,
And the remaining hard phase is composed of WC containing oxygen (O) and nitrogen (N) as a solid solution, and the O and N content of the hard phase is the center of the hard phase. A value measured using an Auger electron spectrometer,
O: 0.2-0.6%
N: 0.1-0.25%
This is characterized by a coated cemented carbide drill that is composed of a cemented carbide alloy that exhibits excellent heat-resistant plastic deformation by high-speed drilling.
[0009]
The reason why the composition of the cemented carbide substrate constituting the cemented carbide drill of the present invention and the average thickness of the hard coating layer are limited as described above will be described below.
(1) Co content of cemented carbide substrate If the Co content as the binder phase forming component is less than 6%, it is not possible to ensure the desired strength and toughness of the substrate, while if the Co content exceeds 16%. Since it becomes easy to cause thermoplastic deformation and the progress of uneven wear is promoted, the Co content is determined to be 6 to 16%.
[0010]
(2) Cr and / or V of cemented carbide substrate
These components include a fine-grained structure in which the growth of the hard phase is remarkably suppressed in a solid solution state in Co forming the binder phase, and the average particle size thereof is preferably 0.7 μm or less. However, if the content of Cr and V components is less than 0.1%, this effect is insufficient. On the other hand, if the content exceeds 3%, these components precipitate as carbides, resulting in strength and toughness. Therefore, the content is determined to be 0.1 to 3%.
[0011]
(3) O content in the hard phase of the cemented carbide substrate If the O content in the hard phase of the cemented carbide substrate is less than 0.2%, the desired excellent high temperature hardness and heat resistance cannot be secured. During the production of the WC powder constituting the hard phase, the proportion of CO gas blended in the nitrogen stream of reduction treatment and the hydrogen stream of carbonization treatment is adjusted to contain 0.2% or more, and excellent high temperature hardness and heat resistance To ensure excellent heat-resistant plastic deformation even in high-heat-generating high-speed drilling, but if its content exceeds 0.6%, the strength of the hard phase itself decreases even if it contains N As a result, chipping (small chipping) is likely to occur on the end cutting edge surface, resulting in shortening the service life. Therefore, the content is determined to be 0.2 to 0.6%. .
[0012]
(4) The N content of the hard phase of the cemented carbide substrate, and if the N content is less than 0.1%, the above-described decrease in strength due to the O content cannot be completely prevented. In the production of the powder, the proportion of CO gas blended in the nitrogen stream of reduction treatment and the hydrogen stream of carbonization treatment is adjusted to contain 0.1% or more, while the content is 0.25%. Exceeding the above results in a decrease in the high temperature hardness and heat resistance improvement effect brought about by the above-mentioned O content, it becomes impossible to ensure the desired high temperature hardness and heat resistance, the progress of wear is remarkably accelerated, the cause of shortening the service life Therefore, the content was determined to be 0.1 to 0.25%.
[0013]
(5) Composition of the hard coating layer Al in (Ti, Al) N constituting the hard coating layer is a solid solution to increase the high temperature hardness and heat resistance with respect to TiN and thereby improve the wear resistance. Therefore, if the X value of the composition formula: (Ti _1-X Al _X ) N is an atomic ratio (hereinafter the same), and less than 0.3, the desired wear resistance cannot be ensured, while the value is If it exceeds 0.7, the X value is set to 0.3 to 0.7 for the reason that chipping and chipping are likely to occur on the end cutting edge surface.
[0014]
(6) Average layer thickness of the hard coating layer If the average layer thickness is less than 0.5 μm, the excellent wear resistance provided by the hard coating layer cannot be secured, while if the average layer thickness exceeds 6 μm, the hard layer is hard. Since chipping easily occurs in the coating layer, the average layer thickness is set to 0.5 to 6 μm.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated carbide drill of the present invention will be specifically described with reference to examples.
WO ₃ powder having an average particle size of 0.5 μm and carbon black of 0.2 μm were prepared as raw material powders. First, these raw material powders were mixed in a ratio of carbon black: 17%, WO ₃ powder: remaining. After blending, adding acetone with a wet ball mill and mixing for 3 hours, drying under reduced pressure, and filling in a carbon boat in a well-unraveled state, this mixed powder is heated to 950-1050 ° C., and the CO gas is changed to 5-15. Reduction treatment is performed under the condition of holding for 3 hours in a nitrogen-CO mixed gas stream blended at a predetermined ratio within a volume% range, and then the heating temperature is set to 1150 to 1250 ° C., and the nitrogen-CO mixed gas stream Is changed to a hydrogen-CO mixed gas stream in which CO gas is blended at a predetermined ratio in the range of 5 to 15% by volume, and carbonization is performed under the condition of holding for 3 hours, and finally the particle size is adjusted. WC powder as a raw material powder for manufacturing a cemented carbide substrate of the coated carbide drill of the present invention containing nitrogen and oxygen shown in Table 1 and having an average particle diameter (hereinafter referred to as the present material WC powder) ) A-1 to a-7 were produced respectively.
[0016]
For comparison purposes, the nitrogen and oxygen contents shown in Table 1 and the average particle diameter are the same under the same conditions except that the reaction atmosphere for the reduction treatment is a nitrogen stream and the reaction atmosphere for the carbonization treatment is a hydrogen stream. WC powders (hereinafter referred to as conventional raw material WC powders) b-1 to b-7 as raw material powders for manufacturing a cemented carbide substrate of the conventional coated carbide drill were manufactured.
[0017]
Next, each of the raw material WC powders a-1 to a-7 of the present invention and the conventional raw material WC powders b-1 to b-7, respectively, has an average particle size of 1.2 μm Co powder and 1.8 μm VC powder. And 2.3 μm Cr ₃ C ₂ powder in the proportions shown in Table 2, wet-mixed with a ball mill for 72 hours, dried under reduced pressure, mixed with wax and solvent for 1 hour, and then extruded. Are formed into long shaped bodies having a predetermined diameter within a range of 4 to 26 mm, and these long shaped bodies are formed in a vacuum atmosphere of 1.3 Pa at a predetermined range of 1380 to 1480 ° C. After sintering by maintaining at the temperature for 1 hour, Ar is introduced while maintaining the temperature rising temperature, and the atmosphere is maintained as a pressurized atmosphere of pressure: 6 MPa for 1 hour, and then cooling HIP treatment is performed. Within the range of 3.3 to 21.0 mm The cemented carbide of the present invention in which a long pressure sintered body having a constant diameter is formed, and the outer diameter of the groove forming portion is set to the dimensions shown in Table 2 by grinding from the pressure sintered body. Substrates A-1 to A-7 and conventional cemented carbide substrates B-1 to B-7 were produced, respectively.
[0018]
Then, these cemented carbide substrates were ultrasonically cleaned in acetone and dried, and each was loaded into a normal arc ion plating apparatus exemplified in FIG. 2, while the cathode electrode (evaporation source) was Each was equipped with Ti-Al alloys with various component compositions, and the inside of the apparatus was evacuated and maintained at a vacuum of 0.5 Pa, and the inside of the apparatus was heated to 500 ° C. with a heater, and then Ar gas was introduced into the apparatus. Introduced into an Ar atmosphere of 10 Pa, in this state, a bias voltage of −800 V was applied to the cemented carbide substrate to clean the surface of the cemented carbide substrate with Ar gas bombardment, and then nitrogen gas was used as a reaction gas in the apparatus. Is introduced into the reaction atmosphere of 6 Pa, and the bias voltage applied to the cemented carbide substrate is lowered to −200 V so that an arc discharge is generated between the cathode electrode and the anode electrode. The hard coating layer made of (Ti, Al) N having the target Al content and the target layer thickness shown in Table 3 is deposited on each surface of the cemented carbide substrate. Carbide drills 1-7 and conventional coated carbide drills 1-7 were produced, respectively.
[0019]
About the present invention coated carbide drills 1 to 7 and the conventional coated carbide drills 1 to 7, using an Auger electron spectroscopy analyzer, the center of any five hard phases in the cemented carbide substrate constituting the same The O content and N content of the parts were measured, and the results are shown in Table 2 as average values.
Table 2 also shows the results of measuring the average particle size of the hard phase in an arbitrary cross section of the cemented carbide substrate constituting these coated carbide drills using a scanning electron microscope.
Further, when the contents of Co, Cr, and V of the cemented carbide substrate were measured, the values were substantially the same as the blend composition.
Furthermore, about each hard coating layer which comprises said invention coated carbide drills 1-7 and conventional coated carbide drills 1-7, the composition of the thickness cross-section center part was measured using an Auger spectroscopic analyzer. Moreover, when the layer thickness was measured using a scanning electron microscope, the composition and the layer thickness substantially the same as the target composition and the target layer thickness were shown in all cases.
[0020]
Next, for the various coated carbide drills described above, wet high speed drilling was performed under the conditions shown in Table 3, using a JIS / SCM440 alloy steel plate material having a planar size of 100 mm × 250 mm and a thickness of 50 mm as a work material. When cutting is performed, the service life is defined as the point when the outer diameter of the groove forming part directly above the cutting edge surface reaches the value shown in Table 3, and the number of drilling operations up to this service life is measured. did. These measurement results are shown in Table 3 as average values.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
[Table 3]

[0024]
【The invention's effect】
From the results shown in Tables 1 to 3, the coated carbide drills 1 to 7 of the present invention have a relatively high content of O and N in the hard phase of the cemented carbide substrate constituting the hard drill. As a result, high temperature hardness and heat resistance are ensured by high-speed drilling with high heat generation, so that normal wear is achieved without the occurrence of thermoplastic deformation that causes uneven wear, especially on the cutting edge surface of the tip. In the conventional coated cemented carbide drills 1 to 7 that maintain and exhibit excellent wear resistance, but the contents of O and N in the hard phase are relatively low, all of them are hard cemented carbide substrates. Due to the high-temperature hardness of the phase and insufficient heat resistance, high-speed drilling tends to cause thermoplastic deformation of the cutting edge surface, and as a result, wear takes an uneven wear form, so the progress of wear is significantly accelerated. And reach the service life in a relatively short time It is clear.
As described above, the coated carbide drill of the present invention exhibits excellent wear resistance over a long period of time not only in drilling under normal conditions but also in high-speed drilling. It is possible to sufficiently satisfy the labor-saving and energy-saving of cutting and cost reduction.
[Brief description of the drawings]
FIG. 1A is a schematic enlarged front view illustrating a coated carbide drill, and FIG. 1B is a schematic cross-sectional view (schematic cross-sectional view) in a direction perpendicular to the center line in the central portion in the longitudinal direction of the groove forming portion. Figure).
FIG. 2 is a schematic explanatory diagram of an arc ion plating apparatus.

Claims

It is composed of a groove forming part and a shank part, and at least the groove forming part is formed on the surface of a cemented carbide substantially composed of a binder phase and a hard phase, with an average layer thickness of 0.5 to 6 μm,
Compositional formula: [Ti _1-X Al _X ] N Ti and Al satisfying an atomic ratio of X: 0.3 to 0.7 as measured by an Auger spectrometer at the center in the thickness direction. In a surface-coated cemented carbide drill made by physical vapor deposition of a hard coating layer made of a composite nitride of
The cemented carbide substrate as a binder phase forming component,
Co: 6-16%
Cr and / or V: 0.1 to 3%,
And the remaining hard phase has a composition made of tungsten carbide containing solid solution of oxygen and nitrogen, and the oxygen and nitrogen content of the hard phase is the Auger electron spectroscopic analyzer for the central portion of the hard phase. Is a value measured using
Oxygen: 0.2-0.6%,
Nitrogen: 0.1-0.25%,
Made of cemented carbide, which is
A surface-coated cemented carbide drill that exhibits excellent heat-resistant plastic deformation in high-speed drilling.