JP3971479B2

JP3971479B2 - Multi-layer coated cemented carbide

Info

Publication number: JP3971479B2
Application number: JP03559097A
Authority: JP
Inventors: 順彦島; 広志植田
Original assignee: Hitachi Tool Engineering Ltd
Current assignee: Moldino Tool Engineering Ltd
Priority date: 1997-02-04
Filing date: 1997-02-04
Publication date: 2007-09-05
Anticipated expiration: 2017-02-04
Also published as: JPH10219452A

Description

【０００１】
【産業上の利用分野】
本発明は硬質被覆層が母材超硬合金との密着性に優れ重断続切削において安定した切削が可能であると共に、各硬質層間の層間密着性にも優れ層間剥離が発生せず、さらに優れた切削性能を発揮する多層被覆超硬合金製切削工具に関する。
【０００２】
【従来の技術】
従来、ＴｉＮ、ＴｉＣＮ、ＴｉＣ、Ａｌ_２Ｏ_３等の硬質皮膜を多層に被覆した被覆超硬合金工具は広く用いられている。多層化することにより、それぞれの皮膜の長所を取り入れる事が可能であるが、反面必然的に界面の数は増加する。一般にこれらの層間の密着性は強いものではなくしばしば層間剥離が発生しこの剥離が工具寿命の低下をもたらす。最近層間の密着性を改善するいくつかの提案（例えば、特開平８−１４１０号公報）もなされているがいまだ満足のいくものではない。また、切削の高率化のため切削送りが増加する傾向にあり、かかる場合、従来の提案では層間剥離も発生するが、さらに母材と多層膜界面での剥離も発生し工具寿命は短い結果であるのが現状である。
【０００３】
また柱状結晶を有するＴｉＣＮ皮膜は耐摩耗性に優れるとともに靱性にも優れ最近頻繁に用いられている。（例えば、特開平５−２６９６０６号，特開平８−１４１０号公報）一方、ＴｉＣなどの皮膜の結晶形態は粒子状であり、例えば、柱状結晶のＴｉＣＮの上に粒状結晶のＴｉＣを積層した場合その界面で結晶構造の不連続性が発生しさらに層間密着性が劣化する結果となる。
【０００４】
また皮膜の中でもＡｌ_２Ｏ_３は酸化物のため、特にＴｉＣやＴｉＮなどの炭化物、窒化物等の他成分皮膜との密着性は悪く従来これを改善すべく下地層とエピタキシャルの関係を保ち成膜する提案（特公平７−８８５８２号公報）や炭化物、窒化物と酸化物の中間的性質を有するＴｉの炭酸化物、窒酸化物、炭窒酸化物を下地に用いる提案（特公昭５５−４７１１０号，特公昭６２−４２２４号）もなされている。しかし今だ満足のいく密着性は得られるに至っていない。特にα型結晶構造を有するＡｌ_２Ｏ_３は下地との界面にピンホール等が発生し易く、今だ十分な密着性が得られるに至っていない。
【０００５】
【発明が解決しようとする課題】
本願発明は上述の層間並びに母材と皮膜の密着性における問題点の解決を目的とし、これに対し各硬質層間の密着性、とりわけ、柱状結晶を有するＴｉＣＮ層を多層の中の一つの層として用いた場合に発生する結晶形態の不連続性に起因する密着性の劣化の防止、さらに、α型結晶構造のＡｌ_２Ｏ_３酸化物層と下地との密着性を著しく改善するものである。さらに母材超硬合金と多層皮膜の密着性も合わせ改善するものである。
【０００６】
【課題を解決するための手段】
本発明者らは、上述の観点からまず一般的に用いられるＴｉＮ−柱状ＴｉＣＮ−粒子状ＴｉＣ、３層構造の多層皮膜を作製し層間剥離現象を調査した。ＴｉＣは一般的条件で成膜すると一番安定である（２００）面に最強のピークを有する粒子状の皮膜が成膜される。これは通常粉末のＴｉＣをＸ線回折した場合に得られ、ＡＳＴＭカードに記載されているものに等しいパターンである。（１１１）面と（２２０）面の強度は成膜条件により多少の変化は認められるが、（２００）＞（１１１）、（２２０）であることには変わりはない。切削試験結果によれば、この場合ＴｉＣＮ層（柱状結晶）とＴｉＣ層（粒子状結晶）の間でのみ剥離が多発し、前述のように結晶形態の不連続性が存在すると、密着性が著しく低下することが、確認された。すなわち、本願の第１の発明は、Ｔｉの窒化物、炭窒化物、炭化物、Ａｌの酸化物の内の少なくとも２種以上を被覆した多層被覆超硬合金において、該被覆層が母材超硬合金側より、第１層がＴｉの炭化物もしくは窒化物もしくは炭窒化物、第２層が柱状結晶を有するＴｉの炭窒化物、第３層がＴｉの炭化物で、Ｘ線回折におけるピークの高さが（１１１）面、（２００）面、（２２０）面において（２００）面のピーク高さが最小で、且つ、該第３層の粗さをＲｍａｘ１．２μｍを超え、Ｒｍａｘ２．０μｍの範囲に粗く設け、第４層がα型結晶構造を有するＡｌの酸化物であることを特徴とする多層被覆超硬合金である。
本願の第２の発明は、前記第１の発明の、第３層を、Ｘ線回折における最強のピークを有する面がその下地層である前記第２層のＸ線回折における最強のピークを有する面と一致させた多層被覆超硬合金である。
【０００７】
【作用】
本発明者らは、柱状結晶を有するＴｉＣＮ状の上に成膜するＴｉＣの成膜条件を鋭意検討した結果、成膜速度を著しく低くした条件下、例えば、反応ガス濃度を著しく低くした条件下で成膜された場合、下地ＴｉＣＮの結晶形態にエピタキシャルに成膜する傾向が発生するという驚くべき事実を確認した。この場合ＴｉＣの結晶形態は一番安定である（２００）面に最強ピークを有するパターンから逸脱し、エピタキシャル成膜の発生頻度を支配するＴｉＣの成膜速度の変化に対し種種の配向パターンを有する結果となる。また、この配向パターンを成膜速度により制御することが可能であるという新しい知見も得られた。
【０００８】
反応ガス濃度を非常に低くすると８０％以上のＴｉＣは下地柱状ＴｉＣＮにエピタキシャルに成膜し、驚くべきことに同じく柱状結晶形態を呈する結果となる。結果、Ｘ線回折における下地ＴｉＣＮの最強ピーク面とＴｉＣの最強ピークは一致する。この場合のＴｉＣＮとＴｉＣ層間の密着力は最も強いことは、結晶構造に不連続性がないことより容易に理解されるところである。反応ガス濃度の多少の増加に伴い、ＴｉＣはエピタキシャルに成膜する頻度は低下し、次に（１１１）面もしくは、（２２０）面に配向する傾向を有するようになる。この場合もＴｉＣは柱状結晶形態を有する傾向にあるため、ＴｉＣＮとこのＴｉＣ層間の密着性は通常の（２００）面に配向した粒子状結晶を有するＴｉＣの場合に較べ著しく良好な結果となることはいうまでもない。また、反応ガス濃度の調整以外では、例えば、成膜温度を非常に低くすることによっても同様に成膜速度を抑え、同様のＴｉＣ皮膜を成膜することが可能である。
【０００９】
ＴｉＣとα型Ａｌ_２Ｏ_３の密着性においてはＴｉＮおよびＴｉＣＮとα型Ａｌ_２Ｏ_３の密着性よりは優れるものの、通常のＴｉＣとの密着性は十分なものではない。その理由は通常の（２００）面に配向したＴｉＣつまり（２００）面に最強のピークを有するＴｉＣにおいては、前述のように、結晶形態は粒子状であり結晶は粒子状に成長する。この場合、結晶粒の大きさはせいぜい０．５μから１．２μであり従ってＴｉＣ表面の面粗さは最大でも１．２Ｓ程度の極めて平坦なものである。この様な平坦な界面においてはアンカー効果が全くなく結果ＴｉＣとＡｌ_２Ｏ_３の密着力は十分なものではない。特に炭化物と酸化物といった全く異種の層間においては、アンカー効果は密着性に対し極めて重要な因子である。この問題を解決すべくＴｉＣとα型Ａｌ_２Ｏ_３の間に中間的性質を有するＴｉＣＯやＴｉＣＮＯを介在させる提案もなされてはいるが、アンカー効果がないことは同様であり密着性を十分に改善するには至っていない。
【００１０】
一方、（１１１）面もしくは（２２０）面に配向したＴｉＣは下地ＴｉＣＮの柱状結晶成長をそのまま引継、柱状に連続成長するため表面粗さは２．０Ｓにもなる。従って、Ａｌ_２Ｏ_３層に対し十分なアンカー効果を発揮し密着性は格段に改善される結果となる。特に下地層と全く同じ配向を有する場合、つまり下地ＴｉＣＮの最強ピークとＴｉＣの最強ピークが一致する場合に表面粗さは最大となり密着性は最大のものとなる。これらＴｉＣとα型Ａｌ_２Ｏ_３の間に中間的性質を有するＴｉＣＯやＴｉＣＮＯを介在させると密着性は更に改善されα型Ａｌ_２Ｏ_３に十分な密着性を付与することは言うまでもない。
【００１１】
母材超硬合金と多層皮膜との密着性においてはＴｉＣを第１層とすることが最も好ましい。これは、母材のＷＣに対してはＴｉＣが最も密着性に優れることによる。この場合は母材成分のＣｏが皮膜中に拡散し第２層の柱状結晶を有するＴｉＣＮ皮膜の特性を多少劣化させる場合もあるため、第１層のＴｉＣと第２層のＴｉＣＮとの間にこの拡散を抑制するため、ＴｉＮを介在させるとより良い結果となる。また第１層はＴｉＣの代わりにＴｉＮであっても母材との密着性は十分である。また必要に応じ最外層はＴｉＮ層とすることにより装飾的意味あいを持たせても良い。以下、実施例に基ずき本発明多層被覆超硬合金を説明する。
【００１２】
【実施例】
母材超硬合金は７．５Ｃｏ−２．５ＴｉＣ−０．５ＴｉＮ−３．０ＴａＣ−残ＷＣ組成（単位は重量％）に統一し、ＷＣ原料は２．８μの市販原料を用いた。この場合母材表面部にはＣｏに富化した１０μの厚さのＷＣ−Ｃｏよりなる、強靱表面層が形成される。また母材の硬さはＨＲＡにおいて９０．０に統一した。ＩＳＯのＣＮＭＧ１２０４０８なるインサートを製作しこれを母材とし、表１に示される各コーティング条件にて各種皮膜を成膜した。本発明多層被覆超硬合金並びに比較被覆超硬合金のコーティング条件については、各表の中に表１中のｃｏａｔ条件番号を記す。尚、圧力は７０〜８０Ｔｏｒｒとした。またｊ条件のＡｌ_２Ｏ_３は８０型結晶構造を有し、ｋ条件においては１００％がα型結晶構造を有するものである。
【００１３】
【表１】

【００１４】
表２に示す本発明多層被覆超硬合金と比較被覆合金を試作し、以下の切削条件にて切削評価を行った。本切削条件下においては、断続的に衝撃が加わるため、母材と皮膜の界面もしくは第２層のＴｉＣＮと第３層のＴｉＣ界面で剥離が発生する。切削後、切削に関与する切れ刃部分の面積と剥離部分の面積の比により剥離率を求めた。切削は１０コーナーにおいて切削を行った。本発明例および比較例の詳細と剥離率の測定結果を表２に併記する。尚、表２中（）で示される面は最大ピークを有する面を、［］で示される面は最小ピークを有する面を示す。
切削条件切削速度２００ｍ／ｍｉｎ
送り０．４ｍｍ／ｒｅｖ
切り込み２ｍｍ
被削材Ｓ５３Ｃ４つ溝
乾式・湿式ｗｅｔ切削
衝撃回数２０００回
尚、膜厚は第１層は０．５μ第２層ＴｉＣＮは５μ、第３層のＴｉＣは４μ、第４層のＡｌ_２Ｏ_３は２μとし、必要に応じ間に介在させるＴｉＮ，ＴｉＣＯ等の層は０．５μとした。また、表２のＴｉＣＮ，ＴｉＣに記載された面は前述の通りである。
【００１５】
【表２】

【００１６】
表２に示される通り本発明多層被覆超硬合金は密着性に優れ取り分け柱状結晶のＴｉＣＮとＴｉＣ層間の密着性に優れることが明らかである。
【００１７】
表２に示した本発明例と比較例を用い、以下の切削条件にて切削試験を実施した。本切削条件はＡｌ_２Ｏ_３の密着性が十分でないと、Ａｌ_２Ｏ_３と下地の間で剥離が発生する条件である。１０分切削後、実施例１と同様に剥離を観察し剥離率を算出した。その結果を表３に示す。
切削条件切削速度３００ｍ／ｍｉｎ
送り０．３ｍｍ／ｒｅｖ
切り込み２．０ｍｍ
被削材ＦＣ２５０
乾式・湿式ｗｅｔ
【００１８】
【表３】

【００１９】
表３より本発明に基ずくα型結晶のＡｌ_２Ｏ_３皮膜の密着性は極めて優れるものであることが確認される。
【００２０】
表１に示すコーティング条件を用い表４に示す本発明例と比較例を製作した。この場合膜厚は第１層は１．０μ、第２層は７．０μ、第３層は２．５μ、第４層は３．５μ、とし、間に介在させるＴｉＮ、ＴｉＣＯ等は０．５μとした。以下に示す切削条件にて、２０分間切削試験を行い境界部の摩耗量を切削開始５分後および２０分後において測定した。この切削条件においては、境界摩耗はまずＡｌ_２Ｏ_３の密着性が十分でないとその剥離が初期に発生し初期より酸化により境界摩耗が発生する。次いで境界部分は黒皮の切削による衝撃により皮膜の層間剥離あるいは母材と皮膜間の剥離が発生する。剥離が発生することにより、境界部の摩耗が著しく発生する。表４に測定した境界摩耗量を併記する。尚、表４中の（）、［］で示す面は表２中と同様である。
切削条件切削速度２５０ｍ／ｍｉｎ
送り０．３５ｍｍ／ｒｅｖ
切り込み２．０ｍｍ
被削材Ｓ５３Ｃ黒皮材
乾式・湿式Ｄｒｙ
【００２１】
【表４】

【００２２】
表４の結果から明らかなように本発明多層被覆超硬合金は各皮膜の層間ならびに母材との密着性に優れ極めて境界摩耗量が少なく長寿命であることが認められる。
【００２３】
【発明の効果】
以上の結果からも明らかなように、本発明による多層被覆超硬合金は、各被覆層間特に、柱状結晶構造を有するＴｉＣＮとその上地層であるＴｉＣ、並びにＴｉＣとα型Ａｌ_２Ｏ_３の密着性に著しく優れ送り量の高い重断続切削、温度衝撃の高い高速切削において、皮膜に剥離が発生する確率が低く、安定した切削並びに長寿命を実現するものである。[0001]
[Industrial application fields]
In the present invention, the hard coating layer has excellent adhesion to the base cemented carbide, and stable cutting is possible in heavy interrupted cutting. Further, the hard coating layer is excellent in interlayer adhesion between hard layers, and delamination does not occur. The present invention relates to a multilayer coated cemented carbide cutting tool that exhibits excellent cutting performance.
[0002]
[Prior art]
Conventionally, a coated cemented carbide tool in which hard coatings such as TiN, TiCN, TiC, and Al ₂ O ₃ are coated in multiple layers has been widely used. By making it multilayer, it is possible to incorporate the advantages of each film, but the number of interfaces inevitably increases. In general, the adhesion between these layers is not strong, and delamination often occurs, and this delamination results in a reduction in tool life. Some proposals (for example, JP-A-8-1410) for improving the adhesion between the layers have been made recently, but they are not yet satisfactory. In addition, the cutting feed tends to increase due to the higher cutting rate. In such a case, the conventional proposal also causes delamination, but also causes delamination at the interface between the base material and the multilayer film, resulting in a short tool life. This is the current situation.
[0003]
Further, TiCN films having columnar crystals are excellent in wear resistance and toughness, and are frequently used recently. (For example, JP-A-5-269606, JP-A-8-1410) On the other hand, the crystal form of the film such as TiC is in the form of particles. For example, when TiC of granular crystals is stacked on TiCN of columnar crystals As a result, discontinuity of the crystal structure occurs at the interface, resulting in deterioration of interlayer adhesion.
[0004]
In addition, Al ₂ O ₃ is an oxide among the films, and in particular, adhesion to other component films such as carbides and nitrides such as TiC and TiN is poor. A proposal for forming a film (Japanese Patent Publication No. 7-88582) and a proposal using Ti carbonate, nitride oxide, or carbonitride having an intermediate property between carbide, nitride and oxide (Japanese Patent Publication No. 55-47110) No., Japanese Examined Patent Publication No. 62-4224). However, satisfactory adhesion has not yet been obtained. In particular, Al ₂ O ₃ having an α-type crystal structure is liable to generate pinholes at the interface with the base, and sufficient adhesion has not yet been obtained.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve the problems in the above-mentioned interlayer and adhesion between the base material and the film. On the other hand, the adhesion between the hard layers, in particular, the TiCN layer having columnar crystals is used as one layer in the multilayer. This prevents the deterioration of the adhesion due to the discontinuity of the crystal form that occurs when used, and remarkably improves the adhesion between the Al ₂ O ₃ oxide layer having an α-type crystal structure and the base. Furthermore, the adhesion between the base cemented carbide and the multilayer coating is also improved.
[0006]
[Means for Solving the Problems]
From the above viewpoint, the present inventors first prepared a commonly used TiN-columnar TiCN-particulate TiC, three-layer multilayer coating and investigated the delamination phenomenon. When TiC is formed under general conditions, a particulate film having the strongest peak on the (200) plane is formed. This is usually obtained when X-ray diffraction of powdered TiC is a pattern equivalent to that described on the ASTM card. Although the intensity of the (111) plane and the (220) plane varies slightly depending on the film forming conditions, it does not change that (200)> (111), (220). According to the cutting test results, in this case, peeling frequently occurs only between the TiCN layer (columnar crystals) and the TiC layer (particulate crystals). It was confirmed that it decreased. That is, the first invention of the present application is a multilayer coated cemented carbide coated with at least two of Ti nitride, carbonitride, carbide, and Al oxide, wherein the coating layer is made of a cemented carbide. From the alloy side, the first layer is Ti carbide or nitride or carbonitride, the second layer is Ti carbonitride with columnar crystals, the third layer is Ti carbide, and the peak height in X-ray diffraction In the (111) plane, (200) plane, and (220) plane, the peak height of the (200) plane is the minimum, and the roughness of the third layer exceeds Rmax 1.2 μm and falls within the range of Rmax 2.0 μm. A multilayer coated cemented carbide characterized in that it is provided roughly and the fourth layer is an oxide of Al having an α-type crystal structure.
The second invention of the present application is the third layer of the first invention, wherein the surface having the strongest peak in X-ray diffraction has the strongest peak in X-ray diffraction of the second layer, which is the underlayer. It is a multi-layer coated cemented carbide matched to the surface.
[0007]
[Action]
As a result of intensive studies on the film formation conditions of TiC formed on the TiCN structure having columnar crystals, the present inventors have found that the film formation rate is extremely low, for example, the reaction gas concentration is extremely low. It was confirmed by the surprising fact that the film formed epitaxially tends to be formed epitaxially in the crystal form of the underlying TiCN. In this case, the crystal form of TiC deviates from the pattern having the strongest peak on the (200) plane, and results in having various orientation patterns with respect to changes in the deposition rate of TiC that govern the frequency of epitaxial deposition. It becomes. Moreover, the new knowledge that this orientation pattern can be controlled by the film formation rate was also obtained.
[0008]
If the reaction gas concentration is very low, 80% or more of TiC is epitaxially deposited on the underlying columnar TiCN, surprisingly resulting in the same columnar crystal morphology. As a result, the strongest peak surface of the base TiCN and the strongest peak of TiC coincide with each other in X-ray diffraction. In this case, the strongest adhesion between TiCN and TiC layers is easily understood from the fact that there is no discontinuity in the crystal structure. With a slight increase in the reaction gas concentration, the frequency of TiC epitaxial deposition decreases, and then tends to be oriented in the (111) plane or the (220) plane. In this case as well, TiC tends to have a columnar crystal form, so that the adhesion between TiCN and this TiC layer is significantly better than that of TiC having particulate crystals oriented in the normal (200) plane. Needless to say. In addition to the adjustment of the reaction gas concentration, for example, it is possible to form the same TiC film by suppressing the film formation rate by making the film formation temperature very low.
[0009]
Although the adhesion between TiC and α-type Al ₂ O ₃ is superior to that between TiN and TiCN and α-type Al ₂ O ₃ , the adhesion with ordinary TiC is not sufficient. The reason is that, as described above, in TiC oriented in the normal (200) plane, that is, TiC having the strongest peak in the (200) plane, the crystal form is grainy and the crystal grows in grain form. In this case, the size of the crystal grains is at most 0.5 μ to 1.2 μ, and therefore the surface roughness of the TiC surface is extremely flat at about 1.2 S at the maximum. At such a flat interface, there is no anchor effect, and as a result, the adhesion between TiC and Al ₂ O ₃ is not sufficient. Especially in completely different layers such as carbide and oxide, the anchor effect is a very important factor for adhesion. In order to solve this problem, proposals have been made to interpose TiCO or TiCNO having intermediate properties between TiC and α-type Al ₂ O ₃ , but it is the same that there is no anchor effect and sufficient adhesion is achieved. It has not yet improved.
[0010]
On the other hand, TiC oriented in the (111) plane or the (220) plane inherits the columnar crystal growth of the underlying TiCN as it is and continuously grows in a columnar shape, so that the surface roughness becomes 2.0S. Therefore, a sufficient anchor effect is exhibited with respect to the Al ₂ O ₃ layer, and the adhesiveness is remarkably improved. In particular, when the base layer has exactly the same orientation, that is, when the strongest peak of the base TiCN coincides with the strongest peak of TiC, the surface roughness is maximum and the adhesion is maximum. Needless to say, when TiCO or TiCNO having intermediate properties is interposed between TiC and α-type Al ₂ O ₃ , the adhesion is further improved and sufficient adhesion is imparted to α-type Al ₂ O ₃ .
[0011]
In terms of adhesion between the base metal cemented carbide and the multilayer coating, it is most preferable to use TiC as the first layer. This is because TiC has the best adhesion to WC as a base material. In this case, the characteristics of the TiCN film having the columnar crystals of the second layer may be slightly deteriorated due to diffusion of the base material component Co into the film, and therefore, between the TiC of the first layer and the TiCN of the second layer. In order to suppress this diffusion, better results are obtained when TiN is interposed. Further, even if the first layer is TiN instead of TiC, the adhesion with the base material is sufficient. If necessary, the outermost layer may be a TiN layer to give a decorative meaning. Hereinafter, the multilayer coated cemented carbide of the present invention will be described based on examples.
[0012]
【Example】
The base cemented carbide was unified to 7.5Co-2.5TiC-0.5TiN-3.0TaC-residual WC composition (unit: wt%), and a commercially available raw material of 2.8 μm was used as the WC raw material. In this case, a tough surface layer made of WC—Co having a thickness of 10 μm enriched with Co is formed on the surface of the base material. The hardness of the base material was unified to 90.0 in HRA. An ISO CNMG120408 insert was manufactured and used as a base material, and various films were formed under each coating condition shown in Table 1. Regarding the coating conditions of the multilayer coated cemented carbide of the present invention and the comparative coated cemented carbide, the coat condition numbers in Table 1 are shown in each table. The pressure was 70 to 80 Torr. In addition, Al ₂ O _{3 in the} j condition has an 80-type crystal structure, and 100% has an α-type crystal structure in the k condition.
[00 13 ]
[Table 1]

[00 14 ]
The multi-layer coated cemented carbide and comparative coated alloy of the present invention shown in Table 2 were prototyped and the cutting evaluation was performed under the following cutting conditions. Under this cutting condition, since impact is applied intermittently, peeling occurs at the interface between the base material and the film or at the interface between the second layer TiCN and the third layer TiC. After cutting, the peeling rate was determined by the ratio of the area of the cutting edge part involved in cutting and the area of the peeling part. Cutting was performed at 10 corners. The details of the examples of the present invention and comparative examples and the measurement results of the peeling rate are shown in Table 2. In Table 2, the surface indicated by () indicates the surface having the maximum peak, and the surface indicated by [] indicates the surface having the minimum peak.
Cutting conditions Cutting speed 200m / min
Feed 0.4mm / rev
Notch 2mm
Work Material S53C 4 Grooves
Dry / wet wet cutting
The number of impacts is 2000 times. The film thickness is 0.5 μm for the first layer, 5 μm for the second layer TiCN, 4 μm for the TiC of the third layer, and 2 μm for the Al ₂ O ₃ of the fourth layer, and intervene as necessary. The layer of TiN, TiCO, etc. was 0.5 μm. The surfaces described in TiCN and TiC in Table 2 are as described above.
[00 15 ]
[Table 2]

[00 16 ]
As shown in Table 2, it is clear that the multilayer coated cemented carbide of the present invention is excellent in adhesion and particularly excellent in adhesion between columnar crystal TiCN and TiC layers.
[00 17 ]
Using the present invention examples and comparative examples shown in Table 2, cutting tests were performed under the following cutting conditions. This cutting conditions when the adhesion of Al ₂ O ₃ is not sufficient, the condition is peeling occurs between the Al ₂ O ₃ and the base. After cutting for 10 minutes, peeling was observed in the same manner as in Example 1 to calculate the peeling rate. The results are shown in Table 3.
Cutting conditions Cutting speed 300m / min
Feed 0.3mm / rev
Notch 2.0mm
Work material FC250
Dry / wet wet
[00 18 ]
[Table 3]

[00 19 ]
From Table 3, it is confirmed that the adhesion of the Al ₂ O ₃ film of α-type crystal based on the present invention is extremely excellent.
[00 20 ]
Using the coating conditions shown in Table 1, inventive examples and comparative examples shown in Table 4 were produced. In this case, the film thickness is 1.0 μm for the first layer, 7.0 μm for the second layer, 2.5 μm for the third layer, and 3.5 μm for the fourth layer. The thickness was 5μ. Under the cutting conditions shown below, a cutting test was performed for 20 minutes, and the amount of wear at the boundary was measured 5 minutes and 20 minutes after the start of cutting. Under these cutting conditions, boundary wear first occurs when the adhesion of Al ₂ O ₃ is not sufficient, and the peeling occurs at an early stage, and boundary wear occurs due to oxidation from the beginning. Next, at the boundary portion, delamination of the film or delamination between the base material and the film occurs due to the impact of cutting the black skin. Due to the occurrence of peeling, the wear of the boundary portion is remarkably generated. Table 4 shows the measured amount of boundary wear. The surfaces indicated by () and [] in Table 4 are the same as those in Table 2.
Cutting conditions Cutting speed 250m / min
Feed 0.35mm / rev
Notch 2.0mm
Work material S53C Black skin material
Dry / Wet Dry
[00 21 ]
[Table 4]

[00 22 ]
As is apparent from the results in Table 4, it can be seen that the multilayer coated cemented carbide of the present invention is excellent in adhesion between the layers of the respective coatings and the base metal and has a very small amount of boundary wear and a long life.
[00 23 ]
【The invention's effect】
As can be seen from the above results, the multilayer coated cemented carbide according to the present invention has an adhesion between TiCN having a columnar crystal structure and TiC as the upper layer, and TiC and α-type Al ₂ O ₃ . In heavy interrupted cutting with excellent feedability and high feed rate, and high-speed cutting with high temperature impact, the probability of delamination on the film is low, and stable cutting and long life are realized.

Claims

In a multilayer coated cemented carbide coated with at least two of Ti nitride, carbonitride, carbide, and Al oxide, the coating layer is from the base cemented carbide side, and the first layer is Ti. Carbide or nitride or carbonitride, second layer is Ti carbonitride having columnar crystals, third layer is Ti carbide, peak height in X-ray diffraction is (111) plane, (200) plane , The (200) plane has a minimum peak height in the (220) plane, and the roughness of the third layer is more than Rmax 1.2 μm and is provided in a range of Rmax 2.0 μm , and the fourth layer is an α-type crystal. A multilayer coated cemented carbide characterized by being an oxide of Al having a structure.

In a multilayer coated cemented carbide coated with at least two of Ti nitride, carbonitride, carbide, and Al oxide, the coating layer is from the base cemented carbide side, and the first layer is Ti. The carbide or nitride or carbonitride, the second layer is Ti carbonitride having columnar crystals, the third layer is Ti carbide, and the surface having the strongest peak in X-ray diffraction is the underlayer. It coincides with the plane having the strongest peak in X-ray diffraction of two layers, and the roughness of the third layer exceeds Rmax 1.2 μm and is roughly provided in the range of Rmax 2.0 μm , and the fourth layer has an α-type crystal structure A multilayer coated cemented carbide characterized by being an oxide of Al having the following:

3. The multilayer coated cemented carbide according to claim 1, wherein a Ti carbonate or carbonitride is interposed between the third layer and the fourth layer.

4. The multilayer coated cemented carbide according to claim 1, wherein a Ti nitride is interposed between the Ti carbide of the first layer and the Ti carbonitride of the second layer. Multi-layer coated cemented carbide.

5. The multilayer coated cemented carbide according to claim 1, wherein the outermost layer is Ti nitride.