JP3762094B2

JP3762094B2 - Method for measuring hardness of coating layer

Info

Publication number: JP3762094B2
Application number: JP08459698A
Authority: JP
Inventors: 将和木下; 加代子西郷; 聡徳重; 和哉清水; 康之廣政
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 1998-03-30
Filing date: 1998-03-30
Publication date: 2006-03-29
Anticipated expiration: 2018-03-30
Also published as: JPH11278967A

Description

【０００１】
【発明の属する技術分野】
本発明は、磁気ヘッドスライダや工具等に好適な無機成分から成る被覆層を有するセラミック焼結体及び該セラミック焼結体に被着された厚さが極めて薄い無機成分から成る被覆層の硬度を非破壊で測定する方法に関するものである。
【０００２】
【従来の技術】
従来より、各種セラミック焼結体の表面に耐摩耗性に優れた被覆層を設けることにより機械的特性を向上させる技術が、磁気ヘッドスライダや工具等をはじめとするさまざまな分野で利用されてきた。
【０００３】
例えば、前記磁気ヘッドスライダとしては、その母材には、その使用目的及び磁気記録媒体の材質により高硬度で耐摩耗性に優れたＡｌ₂Ｏ₃−ＴｉＣや、ＺｒＯ₂、ＢａＴｉＯ₃、フェライト系等の材料が適用され、更にスライダ部の浮上面には、磁気記録媒体との接触で生じる機械的摩耗による損傷を防止するためにスライダ保護膜が被着形成されている。
【０００４】
かかるスライダ保護膜は、一般的に耐摩耗性に優れた高硬度材料を用い、磁気記録媒体からの信号を読み取り易いようにできるだけ薄く被覆する必要があることから、高い硬度を有するダイヤモンド状カーボン（ＤＬＣ）膜が多用されてきたが、該ＤＬＣ膜を母材である高硬度で耐摩耗性に優れたＡｌ₂Ｏ₃−ＴｉＣに被着する場合には、接着強度を高めるためにＳｉＯ₂等の中間層を設けねばならず、製造工程の煩雑さと製造コストの増加を招くという欠点があった。
【０００５】
従って、かかる中間層を設けなくとも良好な接着強度と高硬度を有し、かつ薄膜の形成が容易であるアルミナ（Ａｌ₂Ｏ₃）を主成分とする被覆層を被着形成することが、製造工程の簡便さと低コストの点で主流となってきた。
【０００６】
しかし、前記アルミナ（Ａｌ₂Ｏ₃）を主成分とする被覆層は、スパッタリング法やＣＶＤ法等、公知の成膜方法により比較的容易に形成できるものの、得られた被覆層は、成膜条件や成膜装置により硬度や耐摩耗性等の機械的特性が左右されるため、膜硬度や耐摩耗性等の機械的特性を実際に測定して管理する必要があった。
【０００７】
かかる被覆層の硬度を測定するには、従来からビッカース硬さ試験法や、ヌープ硬さ試験法等、圧子を被覆層表面に押し付けて硬度を測定する押し込み式の硬さ試験法が良く知られているが、厚さが極めて薄い被覆層には、圧子が母材にまで達して被覆層のみの硬度を正確に測定することができず不適切であり、たとえ微小硬度測定装置を用いたとしても圧痕の大きさを計測する際に読み取りが困難となり、測定値がばらつく大きな要因となり、被覆層のみの硬度を正確に評価するには不十分であった。
【０００８】
又、超音波を用いて硬度を測定する方法もあるが、計測される硬度は、被覆層の弾性率や層の厚さ変化に大きく依存するという欠点があり、他に、ダイヤモンド針を用いたスクラッチテスト法でも、硬度は被覆層表面の凹凸によるノイズや、触針の摩耗等の影響を受け易く、いずれも正確な評価が困難であるという欠点があった。
【０００９】
そこで、前記欠点を解消して従来の微小硬度測定装置よりも更に小さい荷重を付加することができると共に、荷重付加速度を一定に調節することができる機構を備えた超微小硬度測定装置により、圧痕の深さが膜厚に対して１０％以下となるように試験荷重を調整して硬度を測定する方法が提案されている（特開平９−２３６５３０号公報参照）。
【００１０】
【発明が解決しようとする課題】
前記提案では、圧痕の読み取りは圧子の変位量を電気的に検出することから読み取り誤差が小さくはなるものの、膜厚が１０μｍ程度未満の極めて薄い測定物では、負荷する荷重が数十ｍｇ以下と小さいために母材表面の凹凸の影響を無視できないことから、測定ばらつきが大きくなり、数回から十数回測定した値の平均より硬度を求めねばならず、信頼性に乏しい上、測定物に被着形成された膜厚が極めて薄いことから、圧痕を付けて硬度を測定する方法では、母材に与える影響が測定物によっては極めて大となり、製品の非破壊検査としては採用できない場合があるという課題があった。
【００１１】
本発明は、前記課題に鑑み成されたもので、その目的は、セラミック焼結体に被着形成した厚さが極めて薄い無機成分から成る被覆層の硬度を、簡便な非破壊法で精度良く測定する方法を提供することにある。
【００１２】
【課題を解決するための手段】
本発明者等は、前記課題を解決するために鋭意検討した結果、セラミック焼結体表面に形成した厚さが極めて薄い無機成分から成る被覆層を直接、硬度測定するのではなく、間接的に硬度を特定することができないか種々試み、かかる被覆層が有する物性の内、密度と硬度の間に有効な相関関係が存在することを見いだし、セラミック焼結体に被着した厚さが極めて薄い無機成分から成る被覆層の密度を、非破壊で測定する方法を検討して本発明に至った。
【００１５】
即ち、本発明の被覆層の硬度測定方法は、先ず、相対密度が９５％以上で０．３ｎｍ以下の表面粗さ（Ｒａ）にまで研磨仕上げしたセラミック焼結体表面に、無機材料をターゲットとしたスパッタリング法で、２０μｍ以下の種々の厚さを有する被覆層を被着形成して標準試料を作製する。
【００１６】
次いで、前記標準試料の無機成分から成る被覆層の単位面積当たりの重量を、蛍光Ｘ線分析法にて前記標準試料のセラミック焼結体から発生するＸ線の強度Ｉを前記被覆層を通して計測し、
【００１７】
【数１】

【００１８】
で表される数式に基づき算出する。
【００１９】
一方、前記標準試料の無機成分から成る被覆層の厚さを、光干渉法やエリプソメトリー法等の公知の光学的手法により測定する。
【００２０】
得られた前記被覆層の単位面積当たりの重量と厚さから、標準試料の無機成分から成る被覆層の密度を算出する。
【００２１】
他方、前記厚さを種々設定した無機成分から成る被覆層を有する標準試料について、超微小硬度測定装置により該被覆層の硬度を測定し、前記標準試料の無機成分から成る被覆層の密度との相関を求める。
【００２２】
以上の相関関係に基づき、硬度未知の無機成分から成る被覆層を被着形成したセラミック焼結体を前記標準試料と同様にして、蛍光Ｘ線分析法と光学的手法により該被覆層の単位面積当たりの重量と厚さをそれぞれ測定して密度を算出し、該密度から前記相関に基づき非破壊法で硬度を求める。
【００２３】
又、前記無機材料は、純度が９９．５％以上のアルミナ（Ａｌ₂Ｏ₃）であることが、更に、前記セラミック焼結体は、Ａｌ₂Ｏ₃−ＴｉＣ焼結体であることが、より望ましいものである。
【００２４】
【作用】
本発明の被覆層の硬度測定方法によれば、鏡面状態に表面仕上げしたセラミック焼結体にスパッタリング法で高純度の無機成分から成る被覆層を被着した標準試料に基づき、該被覆層の単位面積当たりの重量と厚さを蛍光Ｘ線分析法と光学的手法により測定して密度を算出すると共に、前記標準試料の無機成分から成る被覆層を超微小硬度測定装置により硬度を測定し、前記密度と硬度の相関関係を利用して、密度を算出することにより硬度を特定することから、被覆層を設けた母材であるセラミック焼結体の表面粗さの影響が皆無となると共に、被覆層の密度を非破壊法により求めるだけで母材へ悪影響を及ぼすことなく、厚さが極めて薄い無機成分から成る被覆層を有する製品の非破壊検査として精度良く、簡単に硬度を特定できる。
【００２６】
【発明の実施の形態】
以下、本発明の被覆層の硬度測定方法について、詳細に説明する。
【００２７】
図１は、Ａｌ _２Ｏ _３からなる被覆層を有するセラミック焼結体を磁気ヘッドスライダに適用した一実施例の斜視図である。
【００２８】
図において、１は、Ａｌ₂Ｏ₃−ＴｉＯ₂から成る母材のスライダ材料１１と、磁気記録媒体が接する可能性のある浮上面１２の表面にスライダ保護膜として被着形成したアルミナ（Ａｌ₂Ｏ₃）を主成分とする被覆層２とで構成された磁気ヘッドスライダであり、浮上面１２には、一般に空気支持面（ＡＢＳ）を有する構造を成した無機成分から成る被覆層を有するセラミック焼結体である。
【００２９】
前記無機成分から成る被覆層を有するセラミック焼結体において、該被覆層を構成する無機成分としては、アルミナ（Ａｌ₂Ｏ₃）やシリカ（ＳｉＯ₂）、ジルコニア（ＺｒＯ₂）等の酸化物、窒化アルミニウム（ＡｌＮ）や炭化チタン（ＴｉＣ）等の窒化物や炭化物が挙げられるが、磁気ヘッドスライダのスライダ保護膜用としては、母材との接合強度が高いアルミナ（Ａｌ₂Ｏ₃）を主成分とし、その厚さが８μｍ以下の極めて薄いもので、磁気記録媒体からの信号を精度良く読み取れる実用的な厚さを有するものが好適であり、母材のセラミック焼結体もＡｌ₂Ｏ₃−ＴｉＣ焼結体が最適なものである。
【００３０】
このようなＡｌ _２Ｏ _３からなる被覆層を有するセラミック焼結体は、後述の方法である被覆層の硬度が該被覆層の密度との相関から非破壊法で特定されたもので、４００ｋｇｆ／ｍｍ^２未満では、密度が低く、該被覆層の成膜時の異常等により緻密でないため、例えば、スライダ保護膜として適用する際には、磁気記録媒体との接触により短時間で摩耗してしまい、又、各種絶縁層として適用する際には、研磨加工時に絶縁層のみが偏って摩耗してしまうこと等、保護膜としての役割を果たさない。
【００３１】
一方、前記硬度が６２０ｋｇｆ／ｍｍ²を越えると、極めて緻密な状態の膜が得られていることになり、研磨加工時に摩耗量が小さく、加工後に突出した状態となり、例えば、磁気ヘッドスライダとしては、磁気記録媒体と接触する機会が多くなるため、磁気記録媒体の破壊の原因となってしまう。
【００３３】
次に、本発明の被覆層の硬度測定方法は、鏡面仕上げしたセラミック焼結体を母材とし、該母材表面に高純度の無機材料をスパッタリング法にて２０μｍ以下の厚さに種々設定して被着した標準試料について、被覆層の密度を非破壊法で測定し、一方、被覆層の硬度は、標準試料として超微小硬度測定装置を用いて圧痕から測定する方法により決定し、得られた密度と硬度の相関を適用して、硬度未知の無機成分から成る被覆層の硬度を非破壊法で特定するものである。
【００３４】
本発明において、標準試料作製に際し、無機成分から成る被覆層を被着させるセラミック焼結体は、前述のようにＡｌ₂Ｏ₃−ＴｉＣや、ＺｒＯ₂、ＢａＴｉＯ₃、フェライト系等の硬度が高く、耐摩耗性や耐熱性に優れた材料から成るもので、超微小硬度測定装置による被覆層の硬度測定に与える影響を最小とするために、その相対密度は９５％以上の緻密なものでボイド等が表面に極力ないものでなければならず、しかも研磨加工することにより表面粗さ（Ｒａ）が０．３ｎｍ以下となるものでなければならない。
【００３５】
又、前記標準試料に適用する無機成分から成る被覆層としては、高純度の無機材料をターゲットとし、スパッタリング条件としてＡｒガス流量を５０〜１００ＳＣＣＭ、ＲＦ入力を２．８〜３．８ｋＷ、Ａｒガス圧を１．０〜３．０Ｐａに設定して、目標厚さを磁気ヘッドの読み出しや書き込みが可能な上限の厚さから２０μｍ以下、種々設定して被覆する。
【００３６】
尚、前記被覆層の無機成分としては、一般的には、Ａｒガス雰囲気中で純度の高いアルミナ（Ａｌ₂Ｏ₃）をターゲットとしたスパッタリング法が採用できるが、酸素あるいは酸素を含有する不活性ガス雰囲気中でアルミニウム（Ａｌ）をターゲットとした反応性スパッタリング法や、ＣＶＤ等による成膜方法も有効である。
【００３７】
次に、得られた標準試料の無機成分から成る被覆層の単位面積当たりの重量を蛍光Ｘ線分析法で測定するが、これは母材を成すセラミック焼結体中に含有される元素から発生した蛍光Ｘ線が、セラミック焼結体表面に被着形成した被覆層に吸収されるためその強度は減衰することを利用し、検出されるＫα線強度は、下記式
【００３８】
【数１】

【００３９】
で表されことから、該式より被覆層の単位面積当たりの重量ｗ（ｇ／ｃｍ²）を算出するものである。
【００４０】
又、前記蛍光Ｘ線分析法で標準試料の被覆層の単位面積当たりの重量を測定する際には、該被覆層内に雰囲気ガスを取り込んでいる可能性があるため、該被覆層中の元素組成を予め蛍光Ｘ線分析法で確認しておくことが必要である。
【００４１】
更に、蛍光Ｘ線分析法での測定エリアは、測定試料の大きさや、目的に応じて適宜選択する必要があり、例えば、試料の平均的な値を求める際には測定エリアを大きくし、一方、試料内の密度分布を確認する際には測定エリアを小さくして同一試料内を数箇所測定する等の工夫が必要である。
【００４２】
尚、前記被覆層の単位面積当たりの重量の求め方は、非破壊法によるものであるが、前記標準試料については、精度の確保ができれば母材と被覆層を分離して直接重量測定したりすることも可能であり、あるいは試料の浮沈により直接比重を決定する等の方法も採用可能である。
【００４３】
次に、前記被覆層の厚さの測定は、光干渉法やエリプソメトリー法、多重光束干渉法、微分干渉法等の光学的手法が採用し得るが、標準試料では、かかる非破壊法でなくとも、触針法や断面の走査型電子顕微鏡により被覆層の厚さを求めることも可能であるが、硬度未知試料を非破壊法で測定する上では、標準試料も同様に非破壊法で測定するのが測定精度の点からは好ましい。
【００４４】
かくして得られた被覆層の単位面積当たりの重量ｗと、被覆層の厚さｄから、密度ρをρ＝ｗ／ｄの計算式に基づき算出する。
【００４５】
他方、前記厚さを種々設定した被覆層の硬度は、超微小硬度測定装置で測定するが、雰囲気の対流や装置の振動等による外乱を極力低減すると共に、圧子の押し込み深さは被覆層の厚さの１０％以下となるように調整して測定することが肝要である。
【００４６】
以上の結果に基づき、硬度と密度の相関関係を求め、硬度未知の無機成分から成る被覆層を有するセラミック焼結体について、該被覆層の単位面積当たりの重量と厚さをそれぞれ蛍光Ｘ線分析法と光学的手法の非破壊法により測定して密度を算出し、前記相関関係より硬度を特定するものであり、従来、超微小硬度測定装置やスクラッチ試験機では困難であった厚さが１０μｍ以下の被覆層の硬度を精度良く求めることが可能となる。
【００４７】
【実施例】
次に、本発明を以下に詳述するようにして評価した。
【００４８】
直径が４インチ、厚さが５ｍｍの外形寸法を有し、相対密度が９８％、表面粗さ（Ｒａ）が０．２ｎｍのＡｌ₂Ｏ₃−ＴｉＯ₂焼結体を母材とし、該母材表面に、純度９９．５％のアルミナ（Ａｌ₂Ｏ₃）をターゲットとし、Ａｒガス流量が５０〜１００ＳＣＣＭ、ＲＦ入力が２．８〜３．８ｋＷ、Ａｒガス圧が１．０〜３．０Ｐａのスパッタリング条件にて、厚さ２０μｍ以下の種々の厚さのアルミナ被覆層を被着して作製した試料を標準試料とした。
【００４９】
かくして得られた標準試料を用いて、蛍光Ｘ線分析装置で測定エリアを１ｍｍφ、Ｘ線管球がＲｈ、電圧−電流が５０ｋＶ−５０ｍＡとする測定条件により、母材成分であるＴｉのＫα線が、アルミナ被覆層のＡｌ₂Ｏ₃に吸収され減衰した蛍光Ｘ線の強度Ｉを測定し、
【００５０】
【数１】

【００５１】
で表される数式よりアルミナ被覆層の単位面積当たりの重量ｗを算出し、他方、アルミナ被覆層の厚さｄを光干渉法にて測定し、前記アルミナ被覆層の単位面積当たりの重量ｗを厚さｄで除して密度ρを算出した。
【００５２】
尚、前記スパッタリング条件にて被覆したアルミナ被覆層を、蛍光Ｘ線分析法より組成分析を行ったところ、Ａｒが検出されたため、検量線法にてＡｒの定量分析を行い、アルミナ被覆層中に９．６重量％のＡｒが取り込まれていることが分かった。
【００５３】
従って、アルミナ被覆層の組成をＡｌ₂Ｏ₃９０．４重量％、Ａｒ９．６重量％として計算し、単位面積当たりの被覆層重量を求めた。
【００５４】
一方、同一標準試料のアルミナ被覆層の硬度を超微小硬度測定装置により、先端が三角錐の圧子を用い、負荷荷重を圧子の押し込み深さがアルミナ被覆層の厚さの１０％となる条件で押し込み硬さを測定し、外乱の影響を極小とするために、１試料につき１５点測定して平均値をその標準試料のアルミナ被覆層の硬度とした。
【００５５】
以上の測定結果より、縦軸に標準試料のアルミナ被覆層の硬度を、横軸にその密度をプロットし、図２に示す相関を得た。
【００５６】
次いで、前記標準試料の内、アルミナ被覆層が８μｍの厚さを有するものについて、従来のスクラッチテストを比較例としてそれぞれ１５点測定し、その硬度測定の精度をそれぞれ比較した。
【００５７】
【表１】

【００５８】
表からも明らかなように、本発明の非破壊法によるアルミナ被覆層の硬度測定方法は、従来の方法に比べて精度良く測定できることが分かる。
【００５９】
かくして得られた相関から、硬度未知のアルミナ被覆層を被着形成したセラミック焼結体試料を用いて、前記標準試料と同様にして非破壊法で密度を求め、アルミナ被覆層の硬度を特定した。
【００６０】
又、前記硬度未知のアルミナ被覆層を被着形成したセラミック焼結体試料の加工性を評価するために、試料のアルミナ被覆層の面に対して垂直に２００番のダイヤモンドホイールで切断し、断面のアルミナ被覆層にチッピング等の欠陥が認められるものを不良と判定した。
【００６１】
更に、前記切断面を２０００番のダイヤモンドペーストを用いて約１０μｍ研磨し、次いでラップ研磨仕上げした面について触針法で母材とアルミナ被覆層との段差を測定し、段差が１０ｎｍ以上、認められるものを耐摩耗性不良と判定した。
【００６２】
【表２】

【００６３】
以上の結果、試料番号１、６では、アルミナ被覆層の硬度が４００〜６２０ｋｇｆ／ｍｍ^２の範囲外となっており、前記加工性及び／又は耐摩耗性が悪く、アルミナ被覆層が容易に摩耗したり、逆に研磨により母材より突出する等、保護層あるいは絶縁層として不適当であるのに対して、試料番号２〜５では加工性も耐摩耗性も良好であることが確認できた。
【００６４】
尚、本発明は、前記実施例に限定されるものではなく、本発明の要旨を逸脱しない範囲であれば種々変更可能である。
【００６５】
【発明の効果】
叙上の如く、本発明の被覆層の硬度測定方法によれば、鏡面状態に表面仕上げしたセラミック焼結体にスパッタリング法で高純度の無機成分から成る被覆層を被着した標準試料に基づき、該被覆層の単位面積当たりの重量と厚さを蛍光Ｘ線分析法と光学的手法により測定して密度を算出すると共に、前記標準試料の被覆層を超微小硬度測定装置により硬度を測定し、前記密度と硬度の相関関係を決定し、硬度未知の無機成分から成る被覆層を有するセラミック焼結体の密度を非破壊法で算出することにより、厚さが極めて薄い被覆層について特定した硬度が、４００〜６２０ｋｇｆ／ｍｍ^２のセラミック焼結体を得ることができることから、被覆層を設けた母材であるセラミック焼結体の表面粗さにかかかわらず、被覆層の密度を非破壊法により求めるだけで母材へ悪影響を及ぼすことなく、とりわけ厚さが１０μｍ以下の極めて薄い被覆層を有する製品の非破壊検査として精度良く、簡単に硬度を特定でき、得られた被覆層から成る各種保護膜や絶縁層、耐摩耗層として、相手部材を傷付けることなく機能し、信頼性が向上する。
【図面の簡単な説明】
【図１】本発明の被覆層を有するセラミック焼結体を磁気ヘッドスライダに適用した一実施例の斜視図である。
【図２】本発明の被覆層の硬度測定方法における非破壊法により算出した密度と硬度の関係の一例を示す相関図である。
【符号の説明】
１被覆層を有するセラミック焼結体
２無機成分から成る被覆層[0001]
BACKGROUND OF THE INVENTION
The present invention provides a ceramic sintered body having a coating layer made of an inorganic component suitable for a magnetic head slider, a tool, etc., and the hardness of the coating layer made of an inorganic component having a very thin thickness applied to the ceramic sintered body. It relates to a non-destructive measurement method.
[0002]
[Prior art]
Conventionally, a technique for improving mechanical properties by providing a coating layer having excellent wear resistance on the surface of various ceramic sintered bodies has been used in various fields including magnetic head sliders and tools. .
[0003]
For example, as the magnetic head slider, Al ₂ O ₃ —TiC, ZrO ₂ , BaTiO ₃ , ferrite type, which has high hardness and excellent wear resistance depending on the purpose of use and the material of the magnetic recording medium. Further, a slider protective film is deposited on the air bearing surface of the slider portion in order to prevent damage due to mechanical wear caused by contact with the magnetic recording medium.
[0004]
Such a slider protective film is generally made of a highly hard material having excellent wear resistance and needs to be coated as thin as possible so that signals from magnetic recording media can be easily read. DLC) film has been widely used. When the DLC film is applied to Al ₂ O ₃ —TiC, which is a base material having high hardness and excellent wear resistance, SiO ₂ or the like is used to increase the adhesive strength. The intermediate layer must be provided, and there is a drawback that the manufacturing process becomes complicated and the manufacturing cost increases.
[0005]
Therefore, it is possible to deposit and form a coating layer mainly composed of alumina (Al ₂ O ₃ ), which has good adhesive strength and high hardness without providing such an intermediate layer and is easy to form a thin film. It has become mainstream in terms of simplicity of manufacturing process and low cost.
[0006]
However, although the coating layer containing alumina (Al ₂ O ₃ ) as a main component can be formed relatively easily by a known film formation method such as a sputtering method or a CVD method, In addition, since mechanical properties such as hardness and wear resistance are influenced by the film forming apparatus, it is necessary to actually measure and manage mechanical properties such as film hardness and wear resistance.
[0007]
In order to measure the hardness of such a coating layer, indentation type hardness test methods for measuring hardness by pressing an indenter against the surface of the coating layer, such as the Vickers hardness test method and Knoop hardness test method, are well known. However, it is inappropriate for the coating layer that is extremely thin because the indenter reaches the base material and the hardness of only the coating layer cannot be measured accurately. However, it was difficult to read when measuring the size of the indentation, which was a major factor in the variation of the measured value, which was insufficient to accurately evaluate the hardness of only the coating layer.
[0008]
There is also a method of measuring the hardness using ultrasonic waves, but the measured hardness has a drawback that it depends greatly on the elastic modulus of the coating layer and the thickness change of the layer. In addition, a diamond needle was used. Even in the scratch test method, the hardness is easily affected by noise due to unevenness on the surface of the coating layer, wear of the stylus, and the like, and there is a drawback that accurate evaluation is difficult in all cases.
[0009]
Therefore, by eliminating the above disadvantages, it is possible to apply a smaller load than the conventional microhardness measuring device, and by using an ultramicrohardness measuring device equipped with a mechanism that can adjust the load application speed to a constant value. A method has been proposed in which the hardness is measured by adjusting the test load so that the depth of the indentation is 10% or less of the film thickness (see JP-A-9-236530).
[0010]
[Problems to be solved by the invention]
In the proposal, although the reading of the indentation reading errors from electrically detecting the displacement amount of the indenter is small is, the very thin measurement of film thickness is less than about 10 [mu] m, and the load of several tens of mg or less to load Because it is small, the influence of unevenness on the surface of the base material cannot be ignored, so the measurement variation increases, and the hardness must be obtained from the average of the values measured several to dozens of times. Since the deposited film thickness is extremely thin, the method of measuring hardness by making indentations may have a very large effect on the base material and may not be used for nondestructive inspection of products. There was a problem.
[0011]
The present invention has been made in view of the above problems, accuracy and its object is the hardness of the coating layer thickness was deposited and formed on the ceramic sintered body is made of a very thin inorganic components, a simple non-destructive method It is to provide a way to be measured.
[0012]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have not directly measured the hardness of the coating layer made of an inorganic component having a very thin thickness formed on the surface of the ceramic sintered body, but indirectly. Various attempts to determine the hardness, finding that there is an effective correlation between density and hardness among the physical properties of such a coating layer, and the thickness deposited on the ceramic sintered body is extremely thin The present inventors have studied a method for measuring the density of a coating layer made of an inorganic component in a nondestructive manner.
[0015]
That is, in the method for measuring the hardness of the coating layer of the present invention , first, an inorganic material is used as a target on the surface of a ceramic sintered body polished to a surface roughness (Ra) of a relative density of 95% or more and 0.3 nm or less. A standard sample is prepared by depositing and forming coating layers having various thicknesses of 20 μm or less by the sputtering method.
[0016]
Next, the weight per unit area of the coating layer made of an inorganic component of the standard sample is measured through the coating layer by the fluorescent X-ray analysis method and the intensity I of X-rays generated from the ceramic sintered body of the standard sample is measured. ,
[0017]
[Expression 1]

[0018]
It calculates based on the numerical formula represented by.
[0019]
On the other hand, the thickness of the coating layer made of an inorganic component of the standard sample is measured by a known optical method such as a light interference method or an ellipsometry method.
[0020]
From the weight and thickness per unit area of the obtained coating layer, the density of the coating layer made of the inorganic component of the standard sample is calculated.
[0021]
On the other hand, with respect to a standard sample having a coating layer made of an inorganic component having various thicknesses, the hardness of the coating layer is measured by an ultra-micro hardness measuring device, and the density of the coating layer made of the inorganic component of the standard sample is measured. Find the correlation.
[0022]
Based on the above correlation, a ceramic sintered body having a coating layer made of an inorganic component of unknown hardness is formed in the same manner as the standard sample, and the unit area of the coating layer is measured by fluorescent X-ray analysis and optical techniques. The density is calculated by measuring the weight and the thickness per hit, and the hardness is determined from the density by the nondestructive method based on the correlation.
[0023]
The inorganic material may be alumina (Al ₂ O ₃ ) having a purity of 99.5% or more, and the ceramic sintered body may be an Al ₂ O ₃ —TiC sintered body. More desirable.
[0024]
[Action]
According to the hardness measurement method of the covered layer of the present invention, based on a standard sample deposited a coating layer made of a high-purity inorganic components by sputtering the ceramic sintered body surface mirror-finished, of the coating layer The density per unit area is measured by fluorescent X-ray analysis and optical techniques to calculate the density, and the hardness of the coating layer made of inorganic components of the standard sample is measured using an ultra-micro hardness measuring device. Since the hardness is specified by calculating the density using the correlation between the density and the hardness, the influence of the surface roughness of the ceramic sintered body that is the base material provided with the coating layer is completely eliminated. The hardness can be easily and accurately determined as a non-destructive inspection of products having a coating layer composed of an extremely thin inorganic component without adversely affecting the base material simply by determining the density of the coating layer by the non-destructive method. .
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the hardness measurement method of the covered layer of the present invention will be described in detail.
[0027]
Figure 1 is a perspective view of one embodiment of applying the ceramic sintered body having a coating layer of Al ₂ O ₃ in the magnetic head slider.
[0028]
In the figure, reference numeral 1 denotes a base material made of Al ₂ O ₃ —TiO ₂ and alumina (Al ₂₎ deposited as a slider protective film on the surface of the air bearing surface 12 with which the magnetic recording medium may come into contact. O ₃₎ is a magnetic head slider constituted by a covering layer 2 mainly composed of, on the air bearing surface 12, a ceramic having a coating layer made of generally inorganic components form a structure having the air bearing surface (ABS) It is a sintered body.
[0029]
In the ceramic sintered body having a coating layer composed of the inorganic component, the inorganic component constituting the coating layer includes oxides such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), zirconia (ZrO ₂ ), Examples include nitrides and carbides such as aluminum nitride (AlN) and titanium carbide (TiC), but alumina (Al ₂ O ₃ ), which has high bonding strength with the base material, is mainly used for slider protection films of magnetic head sliders. As a component, an extremely thin material having a thickness of 8 μm or less and a practical thickness that can accurately read a signal from a magnetic recording medium is preferable, and a ceramic sintered body as a base material is also Al ₂ O _3. -TiC sintered body is optimal.
[0030]
The ceramic sintered body having such a coating layer made of Al ₂ O ₃ is one in which the hardness of the coating layer , which will be described later, is specified by a nondestructive method from the correlation with the density of the coating layer, and is 400 kgf / If it is less than mm ² , the density is low and it is not dense due to abnormalities during the formation of the coating layer. For example, when it is applied as a slider protective film, it will be worn out in a short time due to contact with the magnetic recording medium. In addition, when applied as various insulating layers, it does not play a role as a protective film, for example, only the insulating layer is unevenly worn during polishing.
[0031]
On the other hand, if the hardness exceeds 620 kgf / mm ² , an extremely dense film is obtained, and the amount of wear during polishing is small, and the film protrudes after processing. For example, as a magnetic head slider, Since there are many opportunities to contact the magnetic recording medium, the magnetic recording medium is destroyed.
[0033]
Next, the coating layer hardness measurement method of the present invention uses a mirror-finished ceramic sintered body as a base material, and variously sets a high-purity inorganic material on the base material surface to a thickness of 20 μm or less by sputtering. The density of the coating layer is measured by a non-destructive method for the standard sample deposited on the other hand, while the hardness of the coating layer is determined by a method of measuring from an indentation using an ultra-micro hardness measuring device as a standard sample. By applying the obtained correlation between density and hardness, the hardness of the coating layer made of an inorganic component whose hardness is unknown is specified by a non-destructive method.
[0034]
In the present invention, the ceramic sintered body on which the coating layer made of an inorganic component is deposited in the preparation of the standard sample has high hardness such as Al ₂ O ₃ —TiC, ZrO ₂ , BaTiO ₃ , and ferrite as described above. It is made of a material with excellent wear resistance and heat resistance, and its relative density is 95% or more in order to minimize the influence on the hardness measurement of the coating layer by the ultra-micro hardness measuring device. The surface must be free from voids and the like, and must have a surface roughness (Ra) of 0.3 nm or less by polishing.
[0035]
Moreover, as a coating layer made of an inorganic component applied to the standard sample, a high-purity inorganic material is a target, Ar gas flow rate is 50 to 100 SCCM, RF input is 2.8 to 3.8 kW, Ar gas as sputtering conditions. The pressure is set to 1.0 to 3.0 Pa, and the target thickness is variously set to 20 μm or less from the upper limit thickness at which reading and writing of the magnetic head can be performed.
[0036]
In general, as the inorganic component of the coating layer, a sputtering method using high-purity alumina (Al ₂ O ₃ ) as a target in an Ar gas atmosphere can be employed, but oxygen or an inert material containing oxygen A reactive sputtering method using aluminum (Al) as a target in a gas atmosphere and a film forming method using CVD or the like are also effective.
[0037]
Next, the weight per unit area of the coating layer made of the inorganic component of the obtained standard sample is measured by fluorescent X-ray analysis, which is generated from the elements contained in the ceramic sintered body constituting the base material. The detected fluorescent X-ray is absorbed by the coating layer formed on the surface of the ceramic sintered body, so that the intensity is attenuated. The detected Kα-ray intensity is expressed by the following formula:
[Expression 1]

[0039]
Therefore, the weight w (g / cm ² ) per unit area of the coating layer is calculated from the above formula.
[0040]
Further, when the weight per unit area of the coating layer of the standard sample is measured by the fluorescent X-ray analysis method, an atmospheric gas may be taken into the coating layer. It is necessary to confirm the composition in advance by fluorescent X-ray analysis.
[0041]
Furthermore, the measurement area in the fluorescent X-ray analysis method needs to be appropriately selected according to the size of the measurement sample and the purpose. For example, when obtaining an average value of the sample, the measurement area is enlarged, When checking the density distribution in the sample, it is necessary to devise measures such as reducing the measurement area and measuring several points in the same sample.
[0042]
The weight per unit area of the coating layer is determined by a nondestructive method. For the standard sample, if the accuracy can be ensured, the base material and the coating layer can be separated and directly measured. It is also possible to adopt a method such as directly determining the specific gravity based on the floating and sinking of the sample.
[0043]
Next, the thickness of the coating layer can be measured by optical methods such as optical interference method, ellipsometry method, multiple beam interference method, and differential interference method. In both cases, it is possible to determine the thickness of the coating layer using the stylus method or cross-sectional scanning electron microscope. However, when measuring a sample of unknown hardness by the nondestructive method, the standard sample is also measured by the nondestructive method. This is preferable from the viewpoint of measurement accuracy.
[0044]
From the weight w per unit area of the coating layer thus obtained and the thickness d of the coating layer, the density ρ is calculated based on the formula ρ = w / d.
[0045]
On the other hand, the hardness of the coating layer with various thicknesses is measured with an ultra-micro hardness measuring device, but disturbance due to convection in the atmosphere, vibration of the device, etc. is reduced as much as possible, and the indentation depth is determined by the coating layer. It is important to adjust the measurement so that the thickness is 10% or less.
[0046]
Based on the above results, the correlation between hardness and density is obtained, and the weight and thickness per unit area of the coating layer of the ceramic sintered body having a coating layer made of an inorganic component whose hardness is unknown are analyzed by fluorescent X-ray analysis. The density is calculated by measuring by the non-destructive method and the optical method, and the hardness is specified by the correlation. It becomes possible to obtain the hardness of the coating layer of 10 μm or less with high accuracy.
[0047]
【Example】
The invention was then evaluated as detailed below.
[0048]
An Al ₂ O ₃ —TiO ₂ sintered body having a diameter of 4 inches, a thickness of 5 mm, a relative density of 98%, and a surface roughness (Ra) of 0.2 nm is used as a base material. On the surface of the material, alumina of 99.5% purity (Al ₂ O ₃ ) is targeted, the Ar gas flow rate is 50 to 100 SCCM, the RF input is 2.8 to 3.8 kW, and the Ar gas pressure is 1.0 to 3. A sample prepared by depositing an alumina coating layer having a thickness of 20 μm or less under a sputtering condition of 0 Pa was used as a standard sample.
[0049]
Using the standard sample thus obtained, the measurement area is 1 mmφ with an X-ray fluorescence analyzer, the X-ray tube is Rh, and the voltage-current is 50 kV-50 mA. Measured the intensity I of fluorescent X-rays absorbed and attenuated by Al ₂ O ₃ of the alumina coating layer,
[0050]
[Expression 1]

[0051]
The weight w per unit area of the alumina coating layer is calculated from the mathematical formula represented by the following formula. On the other hand, the thickness d of the alumina coating layer is measured by an optical interference method, and the weight w per unit area of the alumina coating layer is calculated. The density ρ was calculated by dividing by the thickness d.
[0052]
The composition of the alumina coating layer coated under the sputtering conditions was analyzed by fluorescent X-ray analysis. As a result, Ar was detected, and quantitative analysis of Ar was performed by the calibration curve method. It was found that 9.6 wt% Ar was incorporated.
[0053]
Therefore, the composition of the alumina coating layer was calculated as 90.4% by weight of Al ₂ O ₃ and 9.6% by weight of Ar, and the coating layer weight per unit area was obtained.
[0054]
On the other hand, the hardness of the alumina coating layer of the same standard sample is measured using an ultra-micro hardness measuring device, using a triangular pyramid indenter and the indentation depth of the indenter is 10% of the thickness of the alumina coating layer. In order to measure the indentation hardness and minimize the influence of disturbance, 15 points were measured per sample, and the average value was taken as the hardness of the alumina coating layer of the standard sample.
[0055]
From the above measurement results, the hardness of the alumina coating layer of the standard sample was plotted on the vertical axis and the density on the horizontal axis, and the correlation shown in FIG. 2 was obtained.
[0056]
Next, among the standard samples, the alumina coating layer having a thickness of 8 μm was measured for 15 points using a conventional scratch test as a comparative example, and the accuracy of the hardness measurement was compared.
[0057]
[Table 1]

[0058]
As is apparent from the table, it can be understood that the hardness measurement method of the alumina coating layer according to the non-destructive method of the present invention can be measured with higher accuracy than the conventional method.
[0059]
From the correlation obtained in this way, using a ceramic sintered body sample on which an alumina coating layer of unknown hardness was formed, the density was determined by the non-destructive method in the same manner as the standard sample, and the hardness of the alumina coating layer was specified. .
[0060]
In addition, in order to evaluate the workability of the ceramic sintered body sample on which the alumina coating layer of unknown hardness was deposited, the sample was cut with a No. 200 diamond wheel perpendicular to the surface of the alumina coating layer of the sample, Those in which defects such as chipping were observed in the alumina coating layer were determined to be defective.
[0061]
Further, the cut surface is polished by using a No. 2000 diamond paste for about 10 μm, and then a step difference between the base material and the alumina coating layer is measured by a stylus method on the lapped surface, and a step difference of 10 nm or more is recognized. The product was judged to have poor wear resistance.
[0062]
[Table 2]

[0063]
As a result, the

specimen

number 1,6, the hardness of the alumina coating layer has become out of the range of 400~620kgf / mm ^2, the processability and / or abrasion resistance is poor, the alumina coating layer is easily Although it is not suitable as a protective layer or insulating layer, such as being worn out or protruding from the base material due to polishing, it can be confirmed that sample numbers 2 to 5 have good workability and wear resistance. It was.
[0064]
In addition, this invention is not limited to the said Example, If it is a range which does not deviate from the summary of this invention, it can change variously.
[0065]
【The invention's effect】
As the ordination, according to the hardness measurement method of the covered layer of the present invention, based on a standard sample deposited a coating layer made of a high-purity inorganic components by sputtering the ceramic sintered body surface mirror-finished In addition, the weight and thickness per unit area of the coating layer are measured by fluorescent X-ray analysis and an optical technique to calculate the density, and the hardness of the coating layer of the standard sample is measured using an ultra-micro hardness measuring device. Then, by determining the correlation between the density and the hardness, and calculating the density of the ceramic sintered body having the coating layer made of an inorganic component whose hardness is unknown by the nondestructive method, the coating layer having an extremely thin thickness was specified. Since a ceramic sintered body having a hardness of 400 to 620 kgf / mm ² can be obtained, the density of the coating layer is nondestructive regardless of the surface roughness of the ceramic sintered body that is the base material provided with the coating layer. To the law It is possible to specify the hardness easily and accurately as a non-destructive inspection of products having an extremely thin coating layer with a thickness of 10 μm or less, without adversely affecting the base material just by finding more. Various types of coating layers obtained It functions as a protective film, insulating layer, and wear-resistant layer without damaging the mating member, improving reliability.
[Brief description of the drawings]
FIG. 1 is a perspective view of an embodiment in which a ceramic sintered body having a coating layer of the present invention is applied to a magnetic head slider.
FIG. 2 is a correlation diagram showing an example of the relationship between density and hardness calculated by the nondestructive method in the coating layer hardness measurement method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ceramic sintered compact which has a coating layer 2 The coating layer which consists of an inorganic component

Claims

A coating layer comprising a ceramic sintered body surface having a relative density of 95% or more and a surface roughness (Ra) of 0.3 nm or less, and an inorganic material as a target and the inorganic material component having a thickness of 20 μm or less by sputtering. To prepare a standard sample, and measure the intensity I of X-rays generated from the ceramic sintered body of the standard sample through the coating layer by fluorescent X-ray analysis,

And calculating the weight per unit area of the coating layer of the standard sample, measuring the thickness of the coating layer by an optical method, and then measuring the unit area of the coating layer of the standard sample. After calculating the density from the weight and thickness per unit, and determining the correlation between the density and the hardness of the coating layer composed of the inorganic component of the standard sample measured by the ultra-micro hardness measuring device, from the inorganic component of unknown hardness Calculate the density of the ceramic sintered body with the coating layer formed by measuring the weight and thickness per unit area of the coating layer by the fluorescent X-ray analysis method and the optical method in the same manner as the standard sample. And determining the hardness based on the correlation based on the density.

The method for measuring the hardness of a coating layer according to claim 1 , wherein the inorganic material is alumina (Al ₂ O ₃ ) having a purity of 99.5% or more.

The ceramic sintered _body, Al _{2 O} 3 -TiC claim 1 or hardness measurement method of the coating layer according to claim 2 characterized in that it is a sintered body.