JP3858259B2

JP3858259B2 - Miniature drill made of surface-coated cemented carbide with excellent adhesion with a surface coating layer of ultrafine structure

Info

Publication number: JP3858259B2
Application number: JP34615199A
Authority: JP
Inventors: 安彦田代; 和則佐藤
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 1999-12-06
Filing date: 1999-12-06
Publication date: 2006-12-13
Anticipated expiration: 2019-12-06
Also published as: JP2001162419A

Description

【０００１】
【発明の属する技術分野】
この発明は、超微粒組織の表面被覆層がすぐれた密着性を有し、特に高速穴あけ加工で、すぐれた耐摩耗性と耐チッピング性を発揮する表面被覆超硬合金製ミニチュアドリル（以下、被覆超硬ミニチュアドリルと云う）に関するものである。
【０００２】
【従来の技術】
従来、一般に、被覆超硬ミニチュアドリルとして、例えば図１に概略拡大正面図で示されるように、シャンク部と、外周刃が形成され、かつ前記外周刃形成部分が０．２〜２ｍｍの外径を有する切刃部からなると共に、結合相形成成分としてＣｏ：５〜１６重量％を含有する炭化タングステン基超硬合金（以下、単に超硬合金と云う）の焼結体で構成された基体（以下、超硬基体と云う）の少なくとも前記切刃部の表面に、Ｔｉの炭化物（以下、ＴｉＣで示す）層、窒化物（以下、ＴｉＮで示す）層、炭窒化物（以下、ＴｉＣＮで示す）層、炭酸化物（以下、ＴｉＣＯで示す）層、窒酸化物（以下、ＴｉＮＯで示す）層、および炭窒酸化物（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化合物層と、酸化アルミニウム（以下、Ａｌ₂Ｏ₃で示す）層で構成されたセラミック硬質層からなる表面被覆層を１〜１０μｍの平均厚さで化学蒸着および／または物理蒸着してなる被覆超硬ミニチュアドリルが知られている。
また、上記の超硬基体が、原料粉末として、いずれも０．５〜６μｍの範囲内の所定の平均粒径を有するＷＣ粉末、（Ｔｉ，Ｗ）Ｃ粉末、（Ｔｉ，Ｗ）ＣＮ粉末、（Ｔａ，Ｎｂ）Ｃ粉末、ＴａＣ粉末、ＮｂＣ粉末、ＺｒＣ粉末、ＶＣ粉末、Ｃｒ₃Ｃ₂粉末、Ｃｏ粉末、およびＣｒ粉末などを用い、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、１０^-1Ｔｏｒｒ以上の真空度の真空雰囲気中、５〜１０℃／分の昇温速度で１３７０〜１４７０℃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、炉冷の条件で焼結し、引き続いて通常の条件でＨＩＰ処理を施すことにより、所定の直径を有し、かつ結合相形成成分としてのＣｏ含有量を焼結性および靭性（強度）付与の目的で５〜１６重量％含有した超硬合金で構成された長尺状焼結素材を形成し、この長尺状焼結素材から図１に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。
【０００３】
【発明が解決しようとする課題】
一方、近年の穴あけ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、ボール盤などの高性能化と相俟って、穴あけ加工は、例えば半導体装置のプリント基板などの多層積層板であれば、これを複数枚積み重ねた状態で、かつ高速で行われる傾向にあるが、上記の従来被覆超硬ミニチュアドリルにおいては、これの表面被覆層を構成するセラミック硬質層の基体表面に対する密着性が十分でなく、かつこれ自体高硬度を有するが、靭性のきわめて低いものであり、一方ミニチュアドリルの場合、その穴あけ加工形態から、穴あけ加工速度が速く、かつ穴あけ加工抵抗が大きくなればなるほど、その外周刃外径が０．２〜２ｍｍと細径であることと相俟って、「ねじれ」や「たわみ」が大きくなるものであり、したがってこれを前記のようなきわめて苛酷な穴あけ加工条件で用いると、ミニチュアドリル自体に発生する大きな「ねじれ」や「たわみ」によってセラミック硬質層に、チッピング発生の原因となる剥離が発生し易い状態となり、この結果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、本発明者らは、上述のような観点から、被覆超硬ミニチュアドリルにおいて、超硬基体の表面に対する密着性にすぐれ、かつ特に高速穴あけ加工でミニチュアドリル自体に発生する大きな「ねじれ」や「たわみ」に十分満足に順応する靭性を有する表面被覆層を開発すべく研究を行った結果、通常のスパッタリング装置、例えば図２に概略説明図で示されるスパッタリング装置の基板に、切刃部が例えば図１に示される形状に研削加工され、かつ結合相形成成分として所定量のＣｏを含有する超硬基体を、前記切刃部を下側にして垂下した状態で装着し、またターゲットとして同じく所定量のＣｏを含有する超硬合金を用い、装置内をヒーターで３００〜６００℃に加熱した状態で、圧力：２〜５×１０^-3ＴｏｒｒのＡｒ反応雰囲気中、前記基板には例えば−１００Ｖ、前記ターゲットには例えば−８００Ｖのバイアス電圧を印加して、前記基板とターゲット間にプラズマを発生させた条件でスパッタを行うと、上記超硬基体の表面に、表面被覆層として前記ターゲットを構成する超硬合金と実質的に同じ組成を有するスパッタ蒸着皮膜を形成することができるようになり、この場合上記超硬基体として結合相形成成分であるＣｏの含有量を上記の従来超硬基体と同じく５〜１６重量％とした超硬基体を用いて、特に高速穴あけ加工でミニチュアドリル自体に発生する大きな「ねじれ」や「たわみ」に十分満足に順応することのできる靭性を具備せしめ、かつ上記ターゲットの結合相形成成分であるＣｏの含有量を前記超硬基体に比して相対的に少ない１〜４重量％とした超硬合金を用いて、前記超硬基体に比して相対的に硬質としたスパッタ蒸着皮膜を表面被覆層として１〜１０μｍの平均厚さで形成すると、この結果の被覆超硬ミニチュアドリルにおいては、
（ａ）表面被覆層としての上記スパッタ蒸着皮膜が超硬基体と同種の超硬合金からなるので、前記超硬基体表面に対する密着性が著しく高いものとなり、この結果高速穴あけ加工で発生する大きな「ねじれ」や「たわみ」によって剥離することがなく、したがって外周刃でのチッピング発生が著しく抑制されるようになること。
（ｂ）上記スパッタ蒸着皮膜は、結合相形成成分としてのＣｏの含有量が１〜４重量％と上記超硬基体の５〜１６重量％に比して相対的に低いので、前記超硬基体に比して硬質となることから、耐摩耗性の向上が図れること。
（ｃ）一般に超硬合金の焼結体では、原料粉末として平均粒径で１μｍ以下の微細なＷＣ粉末を用い、かつＷＣ粒成長抑制あるいはＷＣ粒微細化の目的でＣｒ₃Ｃ₂粉末やＣｒ粉末を配合しても、走査型電子顕微鏡による断面組織観察で、ＷＣ粒の平均粒径を０．５μｍ以下にすることはきわめて困難であるが、上記のスパッタ蒸着皮膜は、ＷＣ粒が、上記ターゲットを構成する超硬合金のＷＣ粒の粒径にかかわらず、平均粒径で０．０５μｍ以下の超微粒組織をもつようになり、これによって耐摩耗性の一段の向上がもたらされること。
以上（ａ）〜（ｃ）に示される特性を具備するようになるという研究結果が得られたのである。
【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、
シャンク部と、外周刃が形成され、かつ前記外周刃形成部分が０．２〜２ｍｍの外径を有する切刃部とからなると共に、結合相形成成分としてＣｏ：５〜１６重量％を含有する超硬基体の少なくとも前記切刃部の表面に、結合相形成成分としてＣｏ：１〜４重量％を含有する超硬合金からなり、かつ超微粒組織を有するスパッタ蒸着皮膜で構成された表面被覆層を１〜１０μｍの平均厚さで形成してなる、超微粒組織の表面被覆層がすぐれた密着性を有する被覆超硬ミニチュアドリルに特徴を有するものである。
【０００６】
以下に、この発明の被覆超硬ミニチュアドリルにおいて、これを構成する超硬基体およびスパッタ蒸着皮膜のＣｏ含有量、並びにスパッタ蒸着皮膜の平均厚さを上記の通りに限定した理由を説明する。
（１）超硬基体のＣｏ含有量
その含有量が５重量％未満では、特に高速穴あけ加工でミニチュアドリル自体に発生する大きな「ねじれ」や「たわみ」に順応することのできる十分な靭性、すなわちミニチュアドリル自体に折損の発生がない靭性を確保することができず、一方その含有量が１６重量％を越えると、特に切刃部に熱塑性変形が起り易くなり、これが偏摩耗の原因となることから、その含有量を５〜１６重量％と定めた。
【０００７】
（２）スパッタ蒸着皮膜のＣｏ含有量
その含有量が１重量％未満では、超硬基体表面への密着性が不充分となるばかりでなく、十分な皮膜強度が得られず、一方その含有量が４重量％を越えると、特に高速で穴あけ加工を行った場合の摩耗が急激に進行するようになることから、その含有量を１〜４重量％と定めた。
【０００８】
（３）スパッタ蒸着皮膜の平均厚さ
その平均厚さが１μｍ未満では、所望の耐摩耗性を確保することができず、一方その平均厚さが１０μｍを越えると、外周刃にチッピングが発生し易くなることから、その平均厚さを１〜１０μｍと定めた。
【０００９】
【発明の実施の態様】
つぎに、この発明の被覆超硬ミニチュア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：５．５μｍを有する中粗粒ＷＣ粉末、同０．８μｍの微粒ＷＣ粉末、同１．３μｍのＴａＣ粉末、同１．２μｍのＮｂＣ粉末、同１．２μｍのＺｒＣ粉末、同２．３μｍのＣｒ₃Ｃ₂粉末、同１．５μｍのＶＣ粉末、同１．０μｍの（Ｔｉ，Ｗ）Ｃ粉末、同１．８μｍのＣｏ粉末、および同１．２μｍの炭素（Ｃ）粉末を用意し、これら原料粉末をそれぞれ表１に示される配合組成に配合し、湿式ボールミルで７２時間混合し、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１００Ｐａの圧力で直径：４．４ｍｍの長尺状成形体とし、これらの長尺状成形体を、１０^-3Ｔｏｒｒの真空雰囲気中、７℃／分の昇温速度で１３７０〜１４７０℃の範囲内の所定の温度に昇温し、この温度に１時間保持後、炉冷の条件で焼結し、引き続いてＡｒ雰囲気中、温度：１３４０℃、圧力：１００Ｐａ、保持時間：１時間の条件でＨＩＰ処理を施すことにより、いずれも直径が３．５ｍｍの長尺状焼結素材とし、さらにこれらの長尺状焼結素材から研削加工にて外周刃外径がそれぞれ表１に示される寸法（この場合いずれも切刃部外径は３．５ｍｍ、全長は３８ｍｍ）を有し、かついずれも図１に示される２枚刃形状をもった超硬基体Ａ〜Ｈを製造した。
【００１０】
また、上記の原料粉末を用い、これら原料粉末を表２に示される配合組成に配合し、さらにワックスを加えてアセトン中で２４時間ボールミル混合し、減圧乾燥した後、１ｔｏｎ／ｃｍ²の圧力で所定形状の各種の圧粉体にプレス成形し、これらの圧粉体を、０．０５Ｔｏｒｒの真空雰囲気中、７℃／分の昇温速度で１３７０〜１４７０℃の範囲内の所定の温度に昇温し、この温度に１時間保持後、炉冷の条件で焼結して、いずれも直径：１００ｍｍ×厚さ：１６ｍｍの寸法をもったスパッタ蒸着皮膜形成用ターゲットａ〜ｈをそれぞれ製造した。
【００１１】
ついで、この結果得られた超硬基体Ａ〜Ｈおよびターゲットａ〜ｈを、それぞれ表３に示される組合せで、図２に示される構造のスパッタリング装置に装着し（この場合前記超硬基体は装置内の基板に垂下状態で装着される）、まず、装置内を排気して１×１０−５Ｔｏｒｒの真空に保持しながら、ヒーターで装置内を４５０℃に加熱した後、Ａｒガス、（Ａｒ＋５容量％Ｘｅ）ガス、および（Ａｒ＋１容量％ＣＨ₄）ガスのうちのいずれかを装置内に導入して圧力：１×１０^-3Ｔｏｒｒの雰囲気とし、この状態で前記基板（超硬基体）に−１０００Ｖのバイアス電圧を印加して、前記超硬基体の表面をボンバード洗浄し、引き続いて装置内を圧力：３×１０^-3ＴｏｒｒのＡｒ雰囲気とすると共に、前記基板（超硬基体）には−１００Ｖ、前記ターゲットには−８００Ｖのバイアス電圧を印加して、前記ターゲットａ〜ｈを構成する超硬合金のスパッタ蒸着皮膜を、同じく表３に示される目標厚さで前記超硬基体Ａ〜Ｈの表面全体に形成することにより本発明被覆超硬ミニチュアドリル１〜８をそれぞれ製造した。
【００１２】
また、比較の目的で、上記の超硬基体Ａ〜Ｈの表面全体に、通常の化学蒸着装置を用い、表４に示される条件（表中、ｌ−ＴｉＣＮは、例えば特開平６−８０１０号公報に記載される縦長成長結晶組織をもったＴｉＣＮ層に相当するものであり、これ以外の条件で形成された層はいずれも粒状結晶組織をもつものである。また、α−Ａｌ₂Ｏ₃層はα型結晶構造をもつもの、κ−Ａｌ₂Ｏ₃層はκ型結晶構造をもつものを示す）にて、表５に示される組成および目標厚さのセラミック硬質層を形成することにより従来被覆超硬ミニチュアドリル１〜８をそれぞれ製造した。
【００１３】
なお、上記の本発明被覆超硬ミニチュアドリル１〜８および従来被覆超硬ミニチュアドリル１〜８を構成する超硬基体Ａ〜Ｈ、並びに前記本発明被覆超硬ミニチュアドリル１〜８のスパッタ蒸着皮膜のＣｏ含有量およびＷＣ粒の平均粒径、さらに前記スパッタ蒸着皮膜のＣ含有量をオージェ分析装置および走査型電子顕微鏡を用いての断面組織観察により測定したところ、表３に示される結果を示し、また前記本発明被覆超硬ミニチュアドリル１〜８のスパッタ蒸着皮膜および従来被覆超硬ミニチュアドリル１〜８のセラミック硬質層の厚さを測定したところ、それぞれ表３および表５に示される目標厚さと実質的に同じ平均厚さを示した。
【００１４】
この結果得られた各種の被覆超硬ミニチュアドリルについて、ガラス層とエポキシ樹脂層の交互６層積層板からなる厚さ：１．６ｍｍのプリント基板を４枚重ねたものに表６に示される条件および試験本数：２０本にて高速穴あけ加工試験を行い、ミニチュアドリルの外周刃寸法に５％の摩耗が生じるまでの穴あけ加工数を測定すると共に、使用寿命原因を観察した。これらの測定結果を表６にそれぞれ平均値で示した。
【００１５】
【表１】

【００１６】
【表２】

【００１７】
【表３】

【００１８】
【表４】

【００１９】
【表５】

【００２０】
【表６】

【００２１】
【発明の効果】
表３〜６に示される結果から、本発明被覆超硬ミニチュアドリル１〜８は、いずれもこれを構成するスパッタ蒸着皮膜が同種の超硬合金からなるので、超硬基体表面に対する密着性にすぐれたものとなり、かつ１〜４重量％の低いＣｏ含有量とＷＣ粒の平均粒径が０．０５μｍ以下の超微粒組織を有するので、相対的に高い硬さおよび強度を具備するようになることから、高速穴あけ加工にもかかわらず、外周刃における前記スパッタ蒸着皮膜に剥離の発生がなく、これによって外周刃のチッピング発生が実質的になくなり、この結果すぐれた耐摩耗性を長期に亘って発揮するようになるのに対して、従来被覆超硬ミニチュアドリル１〜８においては、いずれもこれを構成するセラミック硬質層の剥離によるチッピング発生が原因で外周刃の摩耗が急速に進行するようにな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ミニチュアドリルは、通常の条件での穴あけ加工は勿論のこと、自体の「たわみ」や「ねじれ」が大きくなる高速穴あけ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】被覆超硬ミニチュアドリルを例示する概略拡大正面図である。
【図２】スパッタリング装置を例示する概略説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a surface-coated cemented carbide miniature drill (hereinafter referred to as a coating) that has an excellent adhesion with a surface coating layer of an ultrafine-grained structure and exhibits excellent wear resistance and chipping resistance, especially in high-speed drilling. This is called a carbide miniature drill.
[0002]
[Prior art]
Conventionally, as a coated carbide miniature drill, for example, as shown in a schematic enlarged front view in FIG. 1, a shank portion and an outer peripheral blade are formed, and the outer peripheral blade forming portion has an outer diameter of 0.2 to 2 mm. And a substrate composed of a sintered body of a tungsten carbide-based cemented carbide (hereinafter simply referred to as cemented carbide) containing Co: 5 to 16% by weight as a binder phase forming component. Hereinafter, a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) is formed on at least the surface of the cutting edge portion of the carbide substrate. ) Layer, carbon oxide (hereinafter referred to as TiCO) layer, nitrogen oxide (hereinafter referred to as TiNO) layer, and carbonitride oxide (hereinafter referred to as TiCNO) layer. Ti compound layer composed of the above multiple layers and an acid Aluminum (hereinafter, Al ₂ O ₃ in shown) formed by chemical vapor deposition and / or physical vapor deposition of the surface coating layer comprising a ceramic hard layer composed of a layer with an average thickness of 1~10μm coated carbide miniature drill intellectual It has been.
In addition, the above-mentioned cemented carbide substrate is a WC powder having a predetermined average particle size in the range of 0.5 to 6 μm, (Ti, W) C powder, (Ti, W) CN powder, (Ta, Nb) C powder, TaC powder, NbC powder, ZrC powder, VC powder, Cr ₃ C ₂ powder, Co powder, Cr powder, etc., these raw material powders are blended into a predetermined blending composition and wet mixed Then, after drying, a long shaped product having a predetermined diameter is formed by an extrusion press, and this long shaped product is heated at a rate of 5 to 10 ° C./min in a vacuum atmosphere having a degree of vacuum of 10 ⁻¹ Torr or more. The temperature is increased to a predetermined temperature within a range of 1370 to 1470 ° C., held at this increased temperature for 1 to 2 hours, sintered under furnace cooling conditions, and subsequently subjected to HIP treatment under normal conditions. Thus, it has a predetermined diameter and contains Co as a binder phase forming component. A long sintered material composed of a cemented carbide containing 5 to 16% by weight for the purpose of imparting sinterability and toughness (strength) is formed, and this long sintered material is shown in FIG. It is also known that it is manufactured by grinding into a shape to be formed.
[0003]
[Problems to be solved by the invention]
On the other hand, in recent years, there is a strong demand for labor saving, energy saving, and cost reduction of drilling, and along with this, in combination with higher performance of drilling machines, drilling is performed, for example, for printed circuit boards of semiconductor devices. If it is a multi-layer laminate, it tends to be performed at a high speed in a state where a plurality of these are stacked, but in the above-mentioned conventional coated carbide miniature drill, the substrate of the ceramic hard layer constituting the surface coating layer Adhesion to the surface is insufficient and it has high hardness, but it has very low toughness. On the other hand, in the case of a miniature drill, the drilling mode is high, and the drilling resistance is high. The more the outer diameter of the outer peripheral blade is 0.2 to 2 mm, the larger the “twist” or “deflection” becomes. Therefore, if this is used under extremely severe drilling conditions as described above, the ceramic hard layer is likely to be peeled off due to large “twist” or “deflection” that occurs in the miniature drill itself. As a result, the service life is reached in a relatively short time.
[0004]
[Means for Solving the Problems]
Therefore, from the above viewpoint, the present inventors have excellent adhesion to the surface of the cemented carbide substrate in the coated carbide miniature drill, and the large “twist” that occurs in the miniature drill itself particularly in high-speed drilling. As a result of research to develop a surface coating layer having a toughness that adapts satisfactorily to “deflection”, a cutting edge portion is formed on a substrate of a normal sputtering apparatus, for example, the sputtering apparatus schematically shown in FIG. For example, a cemented carbide substrate that is ground into the shape shown in FIG. 1 and contains a predetermined amount of Co as a binder phase forming component is mounted with the cutting edge portion hanging down, and the same as a target. using a cemented carbide containing a predetermined amount of Co, while heating the inside of the apparatus to 300 to 600 ° C. by the heater, pressure: Ar reaction atmosphere of 2 to 5 × 10 ^-3 Torr When the sputtering is performed under the condition that a plasma is generated between the substrate and the target by applying a bias voltage of, for example, −100 V to the substrate and, for example, −800 V to the target, As a surface coating layer, it becomes possible to form a sputter deposition film having substantially the same composition as the cemented carbide constituting the target, and in this case, the content of Co as a binder phase forming component as the cemented carbide substrate. Using a cemented carbide substrate of 5 to 16% by weight like the conventional cemented carbide substrate described above, it is possible to adapt to the large “twist” and “deflection” that occur in the miniature drill itself, especially during high-speed drilling. The toughness that can be achieved, and the content of Co that is a binder phase forming component of the target is set to 1 to 4% by weight, which is relatively smaller than that of the cemented carbide substrate. With hard alloy, to form a sputter deposition film was relatively rigid compared to the cemented carbide substrate with an average 1~10μm thick as the surface coating layer, the coated cemented carbide miniature drills of this result,
(A) Since the sputter deposition film as the surface coating layer is made of the same kind of cemented carbide as the cemented carbide substrate, the adhesion to the surface of the cemented carbide substrate is remarkably high. As a result, a large “ No peeling due to “twisting” or “deflection”, and therefore the occurrence of chipping on the outer peripheral edge is remarkably suppressed.
(B) In the sputter deposition film, the content of Co as a binder phase forming component is 1 to 4 wt%, which is relatively lower than 5 to 16 wt% of the cemented carbide substrate. Since it is harder than, it can improve wear resistance.
(C) In general, a cemented carbide sintered body uses a fine WC powder having an average particle diameter of 1 μm or less as a raw material powder, and Cr ₃ C ₂ powder or Cr for the purpose of suppressing WC grain growth or WC grain refinement Even if the powder is blended, it is extremely difficult to make the average particle diameter of the WC grains 0.5 μm or less by observing the cross-sectional structure with a scanning electron microscope. Regardless of the grain size of the WC grains of the cemented carbide constituting the target, it has an ultrafine grain structure with an average grain size of 0.05 μm or less, which leads to a further improvement in wear resistance.
The research result that the characteristics shown in (a) to (c) are achieved has been obtained.
[0005]
This invention was made based on the above research results,
The shank portion and the outer peripheral blade are formed, and the outer peripheral blade forming portion has a cutting blade portion having an outer diameter of 0.2 to 2 mm, and contains Co: 5 to 16% by weight as a binder phase forming component. A surface coating layer composed of a sputter vapor-deposited film made of a cemented carbide containing Co: 1 to 4% by weight of Co as a binder phase forming component on at least the surface of the cutting edge portion of the cemented carbide substrate and having a microstructure Is characterized by a coated carbide miniature drill having an excellent adhesion with a surface coating layer of an ultrafine grained structure formed with an average thickness of 1 to 10 μm.
[0006]
Hereinafter, in the coated carbide miniature drill of the present invention, the reason for limiting the Co content of the cemented carbide substrate and the sputter deposited film and the average thickness of the sputter deposited film as described above will be described.
(1) Co content of cemented carbide substrate If the content is less than 5% by weight, sufficient toughness to adapt to large “twist” and “deflection” generated in the miniature drill itself, especially in high-speed drilling, that is, It is not possible to secure toughness that does not cause breakage in the miniature drill itself. On the other hand, if its content exceeds 16% by weight, thermoplastic cutting tends to occur especially at the cutting edge, which causes uneven wear. Therefore, the content was determined to be 5 to 16% by weight.
[0007]
(2) Co content of sputter-deposited film If its content is less than 1% by weight, not only the adhesion to the surface of the carbide substrate is insufficient, but also sufficient film strength cannot be obtained, while its content When the amount exceeds 4% by weight, wear particularly when drilling at a high speed starts to progress rapidly, so the content was determined to be 1 to 4% by weight.
[0008]
(3) Average thickness of sputter-deposited film If the average thickness is less than 1 μm, the desired wear resistance cannot be ensured. On the other hand, if the average thickness exceeds 10 μm, chipping occurs on the outer peripheral blade. Since it becomes easy, the average thickness was determined to be 1 to 10 μm.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated carbide miniature drill of the present invention will be described in detail with reference to examples.
As raw material powders, medium coarse WC powder having an average particle diameter of 5.5 μm, fine WC powder of 0.8 μm, TaC powder of 1.3 μm, NbC powder of 1.2 μm, ZrC of 1.2 μm Powder, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, 1.0 μm (Ti, W) C powder, 1.8 μm Co powder, and 1.2 μm carbon ( C) Prepare powders, mix these raw material powders with the composition shown in Table 1, mix for 72 hours with a wet ball mill, dry under reduced pressure, add wax and solvent, mix for 1 hour, and then press And formed into long shaped bodies having a diameter of 4.4 mm at a pressure of 100 Pa at 1370 to 1470 ° C. at a heating rate of 7 ° C./min in a vacuum atmosphere of 10 ⁻³ Torr. The temperature is raised to a predetermined temperature within the range of After holding for a period of time, sintering was performed under furnace cooling conditions, and subsequently, HIP treatment was performed in an Ar atmosphere under the conditions of temperature: 1340 ° C., pressure: 100 Pa, holding time: 1 hour, both having a diameter of 3.5 mm. The outer diameter of the outer peripheral blade is shown in Table 1 by grinding from these longer sintered materials (in this case, the outer diameter of the cutting edge is 3.5 mm, The total length was 38 mm), and the carbide substrates A to H each having the two-blade shape shown in FIG. 1 were manufactured.
[0010]
Further, using the above raw material powders, these raw material powders were blended in the blending composition shown in Table 2, further added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and then at a pressure of 1 ton / cm ² . Various green compacts of a predetermined shape are press-molded, and these green compacts are heated to a predetermined temperature in the range of 1370 to 1470 ° C. at a temperature increase rate of 7 ° C./min in a vacuum atmosphere of 0.05 Torr. Warm, hold at this temperature for 1 hour, and then sinter under furnace cooling conditions to produce sputter-deposited film-forming targets a to h each having dimensions of diameter: 100 mm × thickness: 16 mm.
[0011]
Subsequently, the super-hard substrates A to H and targets a to h obtained as a result are mounted on the sputtering apparatus having the structure shown in FIG. 2 in the combinations shown in Table 3 (in this case, the super-hard substrate is an apparatus). First, the inside of the apparatus is evacuated and kept at a vacuum of 1 × 10 −5 Torr while the inside of the apparatus is heated to 450 ° C. with a heater, and then Ar gas, (Ar + 5 capacity) % Xe) gas and (Ar + 1 volume% CH ₄ ) gas are introduced into the apparatus to create an atmosphere with a pressure of 1 × 10 ⁻³ Torr. In this state, the substrate (carbide substrate) is − A bias voltage of 1000 V is applied to bombard the surface of the super hard substrate, and then the inside of the apparatus is brought to an Ar atmosphere with a pressure of 3 × 10 ⁻³ Torr, and the substrate (super hard substrate) is − 100V, front A bias voltage of -800 V is applied to the target, and the sputter vapor-deposited film of the cemented carbide constituting the targets a to h is applied to the entire surface of the cemented carbide substrate A to H with the target thickness shown in Table 3 as well. The coated carbide miniature drills 1 to 8 of the present invention were manufactured respectively.
[0012]
For the purpose of comparison, a normal chemical vapor deposition apparatus was used on the entire surface of the above-mentioned carbide substrates A to H, and the conditions shown in Table 4 (in the table, l-TiCN is, for example, JP-A-6-8010). is intended to correspond to a TiCN layer having longitudinal growth crystal structure described in JP, other layers formed under the condition of those with both granular crystal structure. Moreover, α-Al ₂ O ₃ By forming a ceramic hard layer having the composition and target thickness shown in Table 5 with a layer having an α-type crystal structure and a κ-Al ₂ O ₃ layer having a κ-type crystal structure) Conventionally coated carbide miniature drills 1 to 8 were produced, respectively.
[0013]
The above-described coated carbide miniature drills 1 to 8 and the conventional coated carbide miniature drills 1 to 8 and the carbide substrates A to H constituting the conventional coated carbide miniature drills 1 to 8 and the sputter-deposited films of the coated carbide miniature drills 1 to 8 of the present invention. Co content and average particle size of WC grains, and C content of the sputter deposited film were measured by observation of a cross-sectional structure using an Auger analyzer and a scanning electron microscope. The results shown in Table 3 were obtained. In addition, when the thicknesses of the sputter-deposited film of the coated carbide miniature drills 1 to 8 and the ceramic hard layer of the conventional coated carbide miniature drills 1 to 8 were measured, the target thicknesses shown in Table 3 and Table 5, respectively. And substantially the same average thickness.
[0014]
For the various coated carbide miniature drills obtained as a result, the conditions shown in Table 6 were obtained by stacking four 1.6 mm-thick printed circuit boards composed of six laminated layers of glass layers and epoxy resin layers. And the number of tests: A high-speed drilling test was performed with 20 drills, and the number of drilling processes until 5% of wear occurred on the outer peripheral edge size of the miniature drill was measured, and the cause of the service life was observed. These measurement results are shown in Table 6 as average values.
[0015]
[Table 1]

[0016]
[Table 2]

[0017]
[Table 3]

[0018]
[Table 4]

[0019]
[Table 5]

[0020]
[Table 6]

[0021]
【The invention's effect】
From the results shown in Tables 3 to 6, the coated carbide miniature drills 1 to 8 of the present invention are all excellent in adhesion to the surface of the carbide substrate because the sputter vapor-deposited film comprising the same is made of the same kind of carbide alloy. It has a low Co content of 1 to 4% by weight and an ultrafine structure with an average particle size of WC grains of 0.05 μm or less, so that it has relatively high hardness and strength. In spite of high-speed drilling, the sputter deposition film on the outer peripheral blade does not peel off, which effectively eliminates the chipping of the outer peripheral blade, resulting in excellent wear resistance over a long period of time. On the other hand, in the conventional coated carbide miniature drills 1-8, all of the outer peripheral blades are caused by chipping caused by peeling of the ceramic hard layer constituting the drill. Worn it is clear that it would like to proceed rapidly.
As described above, the coated carbide miniature drill of the present invention has excellent wear resistance for a long period of time, not only in drilling under normal conditions, but also in high-speed drilling that increases its own "deflection" and "twist". Therefore, it is possible to satisfactorily cope with labor saving, energy saving, and cost reduction in drilling.
[Brief description of the drawings]
FIG. 1 is a schematic enlarged front view illustrating a coated carbide miniature drill.
FIG. 2 is a schematic explanatory view illustrating a sputtering apparatus.

Claims

The shank portion and the outer peripheral blade are formed, and the outer peripheral blade forming portion has a cutting blade portion having an outer diameter of 0.2 to 2 mm, and contains Co: 5 to 16% by weight as a binder phase forming component. A tungsten carbide base cemented carbide containing Co: 1 to 4 wt% as a binder phase forming component on at least the surface of the cutting edge portion of the substrate composed of a sintered body of tungsten carbide base cemented carbide; and A surface-coated cemented carbide miniature formed by forming a surface coating layer composed of a sputter-deposited film having an ultra-fine grain structure with an average thickness of 1 to 10 μm and having an excellent adhesion with the surface coat layer having an ultra-fine grain structure Drill.