JP4166416B2

JP4166416B2 - Method for forming heat shielding ceramic film and heat-resistant component having the film

Info

Publication number: JP4166416B2
Application number: JP2000156865A
Authority: JP
Inventors: 令也新宮; 満堂ヶ原; 直彦吉田; 茂吉竹; 泰治鳥越; 稔大原; 明大森; 秀則白沢; 展周; 二郎伊丹
Original assignee: Kansai Electric Power Co Inc; Mitsubishi Heavy Industries Ltd
Current assignee: Kansai Electric Power Co Inc; Mitsubishi Heavy Industries Ltd
Priority date: 2000-05-26
Filing date: 2000-05-26
Publication date: 2008-10-15
Anticipated expiration: 2020-05-26
Also published as: JP2001335915A

Description

【０００１】
【発明の属する技術分野】
本発明は、発電用ガスタービン等の高温域で使用される機器の部品に適用される熱遮蔽セラミック皮膜の形成方法と、該皮膜を有する耐熱部品に関する。
【０００２】
【従来の技術】
ガスタービンの翼や燃焼筒等の高温域で使用される耐熱部品として、Ｎｉ基耐熱合金基材の表面に、ＭＣｒＡｌＹ（ＭはＣｏ及び又はＮｉ）等の耐高温酸化性・耐高温腐食性に優れる下地合金層を介して、熱遮蔽セラミック皮膜を形成したものが汎用されている。一般的に、このセラミック皮膜は、ＺｒＯ₂にＭｇＯ、ＣａＯ、Ｙ₂Ｏ₃等を加えて安定化させたものであり、プラズマ溶射によって数百μｍ程度の厚みに形成されるのが普通である。
【０００３】
しかるに、上記のような熱遮蔽セラミック皮膜を設けた耐熱部品においても、熱衝撃（加熱−冷却の熱サイクル）の反復により、該セラミック皮膜が剥離し易く、苛酷な使用条件では充分な高温耐久性が得られないという問題があった。特にガスタービンの場合、発電効率の向上のために稼働温度をより高くする傾向にあり、これに伴って各部品の高温耐久性を改善して長寿命化を図ることが強く要望されている。なお、基材への熱影響を緩和するためにセラミック皮膜の膜厚を増加させた場合は、熱衝撃による内部応力が増大するため、上記の剥離はより発生し易くなる。
【０００４】
そこで、上記要望に対処する手段として、近年、熱遮蔽セラミック皮膜に厚み方向の割れ（縦割れ）による柱状組織を形成することが提案されている。これは、前記の界面剥離を生じる主因がセラミック皮膜と下地合金層及び耐熱合金基材との線膨張率の違い（線膨張率：安定化ＺｒＯ₂溶射皮膜…１０〜１１×１０^-6／Ｋ、Ｎｉ基耐熱合金及びＭＣｒＡｌＹ合金…１６×１０^-6／Ｋ）にあることから、予めセラミック皮膜側に割れを形成しておき、この割れによって熱サイクルに伴う膨張・収縮の差を吸収させるというものである。
【０００５】
しかして、従来の提案に係る熱遮蔽セラミック皮膜の前記柱状組織の形成方法としては、電子ビームによる蒸着と酸素イオン照射によって安定化ＺｒＯ₂層を成膜する方法（特開平９−６７６３２号公報）、プラズマ溶射にて成膜した安定化ＺｒＯ₂層の表面に後処理としてパルスレーザを照射する方法（特開平９−３２７７７９号公報）、プラズマ溶射にて安定化ＺｒＯ₂層を形成する際の溶射条件の制御によって溶射単層（１パス）毎に割れを生じさせてゆく方法（特許第２７１００７５号公報）等がある。
【０００６】
【発明が解決しようとする課題】
しかしながら、前記の電子ビームによる蒸着と酸素イオン照射にて成膜する方法は、高コストになると共に、成膜速度が遅いために非能率である上、処理雰囲気の調整等で膜厚を３００μｍ以上にすることが困難であるという難点があった。また前記の成膜後にパルスレーザ照射を行う方法では、後処理としての別工程を必要として作業効率が悪い上、皮膜表面へのパルスレーザ照射では割れが皮膜深部まで進行しにくく、熱衝撃による界面剥離に対する充分な防止効果を得るためにレーザのパワー密度を高めると、穴開き等で皮膜表面が著しく荒れて耐エロージョン性などが大幅に劣化されるという問題があった。更にプラズマ溶射時の条件を制御する方法では、一回の溶射毎に温度を変える等で煩雑な制御操作が必要となり、しかも割れが安定化ＺｒＯ₂層の厚み全体に及ぶため、この割れを通して下地合金層まで直接に腐食性高温雰囲気の影響を受けることになり、安定化ＺｒＯ₂層本来の熱遮蔽機能が充分に発揮されず、基材の熱劣化を生じ易くなるという欠点があった。
【０００７】
本発明は、上述の事情に鑑みて、苛酷な条件下で使用される耐熱部品の表面に、厚み方向の割れによる柱状組織を有する熱遮蔽セラミック皮膜を低コストで能率よく確実に形成し、熱衝撃による界面剥離に対する充分な防止効果を発揮させることを可能にすると共に、前記割れを通した下地への腐食性高温雰囲気の直接的影響を回避し得る手段を提供し、もって高温耐久性に優れて長寿命な耐熱部品を実現することを目的としている。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明に係る熱遮蔽セラミック皮膜の形成方法は、被加工物表面に２層又は３層構造のセラミック皮膜を形成する方法において、その２層構造の上層ならびに３層構造の中間層の形成に際し、溶射域の被加工物表面にレーザ照射しつつ該表面にセラミック材料をプラズマ溶射することにより、前記２層構造の上層ならびに３層構造の中間層に厚み方向の割れによる柱状組織を形成することを特徴としている。すなわち、この方法によれば、プラズマ溶射されたセラミック材料が同時に溶射面に照射されているレーザ光によって高温に加熱され、溶射粒子間の結合力が増して組織は緻密化すると共に、溶射面の移動によってレーザ照射域から外れて急速に冷却固化する際の収縮に伴って皮膜厚み方向の割れが網目状に生じ、この割れを生じた単層の積み重なりによって柱状組織が形成される。そして、この場合、２層構造の上層ならびに３層構造の中間層をレーザ照射下でのプラズマ溶射にて形成するから、熱遮蔽セラミック皮膜の柱状組織を構成する割れが下地面まで達していない状態になり、割れを通して腐食性高温雰囲気の影響が下地が直接に及ぶことはない。また、この柱状組織の形成においては、通常のプラズマ溶射による成膜工程で溶射面にレーザ照射を行うのであるから、別途に工程を追加する必要はなく、またレーザ照射を停止すれば、そのまま割れのない溶射皮膜が形成されることになるから、割れの深さや形成位置を任意に設定できることになる。
【００１０】
請求項２の発明では、上記請求項１の熱遮蔽セラミック皮膜の形成方法において、ＺｒＯ₂ を主成分とするセラミック材料を用いるものとしているから、形成される皮膜が優れた熱遮蔽機能を発揮するものとなる。
【００１１】
請求項３の発明では、上記請求項１又は２の熱遮蔽セラミック皮膜の形成方法において、プラズマ溶射を照射面でのレーザパワー密度が１００〜３５０Ｗ／ｍｍ² となるレーザ照射下で行うものとしている。この場合、レーザパワー密度が適度であるため、溶射皮膜に下地との界面剥離の防止に適した良好な状態の柱状組織を形成できる。
【００１２】
請求項４の発明では、上記請求項１〜３のいずれかの熱遮蔽セラミック皮膜の形成方法において、プラズマ溶射をＹＡＧレーザの連続発振によるレーザ照射下で行うものとしており、そのレーザービームの特性から、溶射皮膜に良好な柱状組織を形成し易い。
【００１３】
請求項５の発明に係る耐熱部品は、部品表面にプラズマ溶射層からなる２層又は３層構造の熱遮蔽セラミック皮膜を備え、該セラミック皮膜の２層構造の上層もしくは３層構造の中間層が請求項１〜４のいずれかに記載のレーザ照射下でのプラズマ溶射にて形成された皮膜厚み方向の割れによる柱状組織を有すると共に、前記２層構造の下層もしくは３層構造の上下層がプラズマ溶射のみで形成された連続組織を有してなるものとしている。この耐熱部品では、セラミック皮膜の柱状組織によって当該皮膜と下地との熱衝撃による界面剥離が防止されると共に、該柱状組織を構成する割れが下地面まで達しておらず、割れを通して腐食性高温雰囲気の影響が下地が直接に及ばないから、部品全体として高温耐久性に優れて長寿命となる。
【００１４】
請求項６の発明は、上記請求項５の耐熱部品において、Ｎｉ基耐熱合金基材の表面に、ＭＣｒＡｌＹ（ＭはＣｏ及び又はＮｉ）合金層を介してＺｒＯ₂ を主体とする前記熱遮蔽セラミック皮膜が形成されてなるものとしている。この耐熱部品では、基材、下地合金層、セラミック層の各材質より、耐高温腐食性、耐高温酸化性、高温耐久性等の熱的性質が特に優れたものとなる。
【００１５】
【発明の実施の形態】
以下、本発明に係る熱遮蔽セラミック皮膜の形成方法について、図面を参照して具体的に説明する。図１において、１は被加工物である耐熱合金よりなる基材、２は基材１上にプラズマ溶射にて形成された耐高温腐食性・耐高温酸化性の下地合金層、３は下地合金層２上に成膜中の熱遮蔽セラミック皮膜である。
【００１６】
図１に示すように、熱遮蔽セラミック皮膜３の成膜は、基材１を矢印ａの如く所定速度で進行させつつ、定位置にプラズマ溶射機（図示省略）からのプラズマスプレーＰを溶射して行うが、この溶射域Ｚに同時にレーザ照射装置（図示省略）から出射されるレーザービームＬのスポットを重畳させる。これにより、溶射ノズルから溶着面に辿り着く飛行過程で温度低下した溶射粒子が溶射域Ｚで再加熱されて溶融し、溶融粒子間の結合力が増して組織は緻密化すると共に、溶射域Ｚの移動によってレーザービームＬのスポットから外れて急速に冷却固化するが、この固化収縮に伴って皮膜厚み方向の割れ４…が図２に示すように皮膜表面から見て網目状に生じる。
【００１７】
しかして、溶射条件によって異なるが、溶射粒子の径は５０μｍ前後であり、一回の溶射（１パス）で成膜される単層の厚みは２０μｍ内外であるため、セラミック皮膜３が所要の厚さになるまで溶射を重ねることになるが、レーザ照射下でのプラズマ溶射を続けてゆくと、後から形成される単層の固化収縮に伴う割れ４…はその下の単層に生じている割れ４…のパターンに追従して発生し易いため、割れ４…の殆どが皮膜の厚み方向に延びてゆくことになる。
【００１８】
一方、このような皮膜形成機構においてレーザ照射のみを停止すれば、通常のプラズマ溶射となって割れ４…のない皮膜が形成される。そこで、下地合金層２上への成膜開始から溶射層の厚みがある程度になるまではレーザ照射を停止しておき、以降はレーザ照射を行いつつプラズマ溶射すれば、図３（Ａ）に示すように、割れ４…による柱状組織の上層３１ａと連続組織の下層３２ａとの二層構造をなす熱遮蔽セラミック皮膜３Ａが形成される。また、この二層構造上に更にレーザ照射を停止してプラズマ溶射すれば、図３（Ｂ）に示すように、連続組織の上下層３２ａ，３２ｂの間に柱状組織の中間層３１ｂを挟んだ三層構造をなす熱遮蔽セラミック皮膜３Ｂが形成される。
【００１９】
しかして、これら二層及び三層構造の熱遮蔽セラミック皮膜３Ａ，３Ｂを設けた耐熱部品では、前者の下層３２ａ並びに後者の中間層３１ｂが柱状組織を有するため、発電用ガスタービン等の部品として使用中に熱衝撃を受けた際、これら皮膜３Ａ，３Ｂと下地合金層２及び基材１との線膨張率の違いによる伸縮の差があっても、内部応力が該柱状組織を構成する割れ４…によって吸収緩和され、セラミック皮膜３Ａ，３Ｂと下地合金層２との間の界面剥離が効果的に抑えられる上、割れ４…は下地合金層２に達していないため、この下地合金層２が割れ４…を通して直接に腐食性高温雰囲気の影響を受けることはなく、またプラズマ溶射によってセラミック皮膜３Ａ，３Ｂを厚く形成して充分な熱遮蔽機能を付与でき、もって苛酷な使用条件でも充分な高温耐久性が得られる。
【００２０】
なお、熱遮蔽セラミック皮膜の充分な高温耐久性を確保する上で、レーザ照射下でのプラズマ溶射にて成膜される柱状組織の部分は、皮膜厚さの１０％以上となるように設定するのがよい。ただし、割れを通した下地への腐食性高温雰囲気の影響を回避するため、下地面から少なくとも皮膜厚さの７％まではプラズマ溶射のみで成膜される連続組織とすることが好ましい。
【００２１】
ここで、熱遮蔽セラミック皮膜３，３Ａ，３Ｂに用いられるセラミック材料としては、ＭｇＯ、ＣａＯ、Ｙ₂Ｏ₃等を加えて安定化させたＺｒＯ₂が好適に使用される。また基材１の耐熱合金としては、インコネル等のＮｉ基耐熱合金が好適である。下地合金層２としては、耐高温腐食性及び耐高温酸化性に優れるものであればよいが、特にＭＣｒＡｌＹ（ＭはＣｏ及び又はＮｉ）合金が推奨される。
【００２２】
レーザ照射は、照射面でのレーザパワー密度が１００〜３５０Ｗ／ｍｍ²となる範囲が好適であり、同パワー密度が１００Ｗ／ｍｍ²未満では割れ４…が形成されにくく、逆に３５０Ｗ／ｍｍ²を越えると皮膜の表面荒れが生じ易くなる。また、使用するレーザの種類は特に制約されないが、小型で取扱い性のよいＹＡＧレーザの連続発振によるレーザビームによれば、その特性から溶射皮膜に良好な柱状組織を形成し易い。しかして、図１で示すようにプラズマスプレーＰの溶射域ＺにレーザービームＬのスポットを重畳させて、且つレーザパワー密度を適度に設定する上で、レーザービームＬは焦点から深浅いずれかに外れた位置で照射面に当て、もって照射スポットが溶射域Ｚに略一致するように設定することが望ましい。
【００２３】
【実施例】
以下に、本発明の実施例を参考例と共に具体的に説明する。これら実施例及び参考例では、インコネル合金からなる発電用ガスタービン翼を基材とし、この基材上に減圧プラズマ溶射によって成膜した１００μｍ厚のＣｏＮｉＣｒＡｌＹ合金層を下地とし、この上に熱遮蔽セラミック皮膜３を大気中プラズマ溶射もしくはレーザ照射下での大気中プラズマ溶射によって成膜する。そのプラズマ溶射条件とレーザ照射条件を表１及び表２に示す。
【００２４】
【表１】

【００２５】
【表２】

【００２６】
実施例１
前記ＣｏＮｉＣｒＡｌＹ合金層を形成した基材をロボットに持たせる一方、プラズマ溶射機とレーザ照射装置とを図１の如くプラズマスプレーＰの溶射域ＺにレーザービームＬのスポットが重畳するように固定し、図１の矢印ａの如く基材１側を移動させながら、８重量％のＹ₂Ｏ₃を添加したＺｒＯ₂を溶射材料として、溶射開始からプラズマ溶射のみで１５パスの成膜を行い、以降についてはレーザビームＬを焦点より１５ｍｍ下の位置（照射面でのパワー密度＝２８３Ｗ／ｍｍ²）で照射しつつ６パスの成膜を行うことにより、３００μｍ厚の熱遮蔽セラミック皮膜を形成した。
【００２７】
参考例１
レーザビームＬの照射を焦点より２５ｍｍ下の位置（照射面でのパワー密度＝１０２Ｗ／ｍｍ²）で行った以外は、実施例１と同様にして３００μｍ厚の熱遮蔽セラミック皮膜を形成した。
【００２８】
実施例２
溶射開始からプラズマ溶射のみで８パスの成膜を行い、次いでレーザビームＬを実施例１と同位置で照射しつつ６パスの成膜を行い、更にプラズマ溶射のみで４パスの成膜を行うことにより、３００μｍ厚の熱遮蔽セラミック皮膜を形成した。
【００２９】
参考例２
溶射開始から終了までをプラズマ溶射のみで成膜し、３００μｍ厚の熱遮蔽セラミック皮膜を形成した。
【００３０】
上記実施例１，２と参考例１で形成した熱遮蔽セラミック皮膜の断面組織の電子顕微鏡写真（×１５０）を、実施例１は図４、参考例１は図５、実施例２は図６にそれぞれ示す。図４から明らかなように、実施例１にて形成されたセラミック皮膜は、厚み方向に綺麗に揃った割れによる明瞭な柱状組織の上層と、割れのない連続組織の下層との二層構造をなしている。これに対し、参考例１にて形成されたセラミック皮膜は、図５に示すように上部に明瞭な割れが殆ど認められず、柱状組織を形成するためのレーザービームの強度が不足していることが判る。一方、図６より、実施例２にて形成されたセラミック皮膜は、連続組織の上下層の間に柱状組織の中間層を挟んだ三層構造をなすことが判る。
【００３１】
〔熱衝撃試験〕
次に、実施例１，２及び参考例１，２で熱遮蔽セラミック皮膜を形成したガスタービン翼について、加熱炉を用い、図７に示すように４．５分で９９０℃まで加熱後に４．５分で６０℃まで冷却する熱サイクルを１回の熱衝撃として、この熱衝撃を繰り返し与え、該セラミック皮膜が剥離するまでの熱衝撃回数を調べた。その結果を次の表３に示す。
【００３２】
【表３】

【００３３】
表３の結果から、プラズマ溶射のみで形成した参考例２のセラミック皮膜は僅か４回の熱衝撃で剥離したのに対し、参考例１のセラミック皮膜はある程度まで熱衝撃に耐えても不充分であり、実施例１，２のセラミック皮膜では１０００回以上の熱衝撃によっても剥離が起こらず、本発明によるセラミック皮膜は極めて高温耐久性に優れていることが判る。
【００３４】
【発明の効果】
請求項１の発明によれば、被加工物表面に２層又は３層構造のセラミック皮膜を形成する方法において、その２層構造の上層ならびに３層構造の中間層の形成に際し、溶射域の被加工物表面にレーザ照射しつつ該表面にセラミック材料をプラズマ溶射することから、前記２層構造の上層ならびに３層構造の中間層として、熱衝撃による剥離を生じにくい柱状組織を有する当該皮膜を確実に且つ容易に低コストで形成でき、この皮膜を苛酷な高温域で使用される耐熱部品の表面に設けて高温耐久性を大きく改善することができる。また、この方法では、柱状組織を構成する割れが下地面まで達せず、この割れを通して腐食性高温雰囲気が下地へ直接に及ぶのを防止できるものを形成できる。しかも、前記柱状組織の形成においては、通常のプラズマ溶射による成膜工程で溶射面にレーザ照射を行えばよいから、前記柱状組織の形成のために別途に工程を追加する必要はなく、それだけ加工能率がよい上、レーザの照射と停止を行うだけで皮膜内の任意の部位ならびに任意の面領域に柱状組織を形成して、他をプラズマ溶射のみによる連続組織とすることができる。
【００３６】
請求項２の発明によれば、上記の熱遮蔽セラミック皮膜として、特に熱遮蔽機能に優れるものを形成できる。
【００３７】
請求項３の発明によれば、上記の熱遮蔽セラミック皮膜として、下地との界面剥離の防止に適した良好な状態の柱状組織を有するものを形成できる。
【００３８】
請求項４の発明によれば、上記の熱遮蔽セラミック皮膜の形成方法において、当該皮膜に良好な柱状組織を容易に形成できるという利点がある。
【００３９】
請求項５の発明によれば、耐熱部品として、その表面に設けた熱遮蔽セラミック皮膜の熱衝撃による界面剥離を生じにくく、且つ腐食性高温雰囲気の影響が下地に直接に及ぶことがなく、もって全体として高温耐久性に優れて長寿命なものが提供される。
【００４０】
請求項６の発明によれば、上記の耐熱部品として、耐高温腐食性、耐高温酸化性、高温耐久性等の熱的性質に特に優れたものが提供される。
【図面の簡単な説明】
【図１】本発明に係る熱遮蔽セラミック皮膜の形成方法を模式的に示す斜視図である。
【図２】同形成方法による一回のプラズマ溶射で成膜される熱遮蔽セラミック皮膜の単層の斜視図である。
【図３】同形成方法による熱遮蔽セラミック皮膜を備えた耐熱部品を示し、（Ａ）は二層構造の該皮膜を有する耐熱部品の断面図、（Ｂ）は三層構造の該皮膜を有する耐熱部品の断面図である。
【図４】実施例１で形成した熱遮蔽セラミック皮膜の断面組織を示す電子顕微鏡写真図である。
【図５】参考例１で形成した熱遮蔽セラミック皮膜の断面組織を示す電子顕微鏡写真図である。
【図６】実施例２で形成した熱遮蔽セラミック皮膜の断面組織を示す電子顕微鏡写真図である。
【図７】熱衝撃試験の熱サイクル図である。
【符号の説明】
１基材（被加工物）
２下地合金層
３，３Ａ，３Ｂ熱遮蔽セラミック皮膜
３１ａ柱状組織の上層
３１ｂ連続組織の下層
３２ａ連続組織の上層
３２ｂ柱状組織の中間層
３２ｃ連続組織の下層
４割れ
Ｐプラズマスプレー
Ｌレーザービーム
Ｚ溶射域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a heat-shielding ceramic coating applied to parts of equipment used in a high temperature region such as a gas turbine for power generation, and a heat-resistant component having the coating.
[0002]
[Prior art]
As heat-resistant parts used in high-temperature areas such as gas turbine blades and combustion cylinders, it has high-temperature oxidation resistance and high-temperature corrosion resistance such as MCrAlY (M is Co and / or Ni) on the surface of Ni-base heat-resistant alloy base materials A material in which a heat-shielding ceramic film is formed through an excellent base alloy layer is widely used. Generally, this ceramic film is stabilized by adding MgO, CaO, Y ₂ O ₃ or the like to ZrO ₂ and is usually formed to a thickness of about several hundred μm by plasma spraying. .
[0003]
However, even in heat-resistant parts provided with a heat-shielding ceramic coating as described above, the ceramic coating is easy to peel off due to repeated thermal shocks (heating-cooling thermal cycle), and sufficient high-temperature durability under severe conditions There was a problem that could not be obtained. In particular, in the case of a gas turbine, there is a tendency to increase the operating temperature in order to improve the power generation efficiency, and accordingly, there is a strong demand for improving the high temperature durability of each component and extending the life. In addition, when the film thickness of the ceramic film is increased in order to mitigate the thermal influence on the base material, the internal stress due to thermal shock increases, so that the above-described peeling is more likely to occur.
[0004]
Therefore, in recent years, it has been proposed to form a columnar structure due to cracks in the thickness direction (longitudinal cracks) in the heat-shielding ceramic film as a means for coping with the above demand. This is due to the difference in linear expansion coefficient between the ceramic film, the base alloy layer and the heat-resistant alloy substrate (linear expansion coefficient: stabilized ZrO ₂ sprayed coating ... 10 to 11 × 10 ^-6 / K). , Ni-base heat-resistant alloy and MCrAlY alloy ... 16 × 10 ⁻⁶ / K), cracks are formed in advance on the ceramic film side, and this crack absorbs the difference in expansion and contraction associated with the thermal cycle. Is.
[0005]
Therefore, as a method of forming the columnar structure of the heat-shielding ceramic film according to the conventional proposal, a method of forming a stabilized ZrO ₂ layer by electron beam deposition and oxygen ion irradiation (Japanese Patent Laid-Open No. 9-67632). , A method of irradiating a surface of a stabilized ZrO ₂ layer formed by plasma spraying with a pulsed laser as post-processing (Japanese Patent Laid-Open No. 9-327779), thermal spraying when forming a stabilized ZrO ₂ layer by plasma spraying There is a method (Japanese Patent No. 2710075) or the like of generating cracks for each sprayed single layer (one pass) by controlling the conditions.
[0006]
[Problems to be solved by the invention]
However, the method of forming a film by electron beam evaporation and oxygen ion irradiation is expensive and inefficient because the film forming speed is slow, and the film thickness is 300 μm or more by adjusting the processing atmosphere. There was a difficulty that it was difficult to make. In addition, the method of performing pulse laser irradiation after the film formation described above requires a separate process as post-processing, and the work efficiency is poor. Further, the pulse laser irradiation on the film surface is difficult to progress to the deep part of the film, and the interface caused by thermal shock If the power density of the laser is increased in order to obtain a sufficient prevention effect against peeling, there is a problem that the surface of the coating is remarkably rough due to perforations and the erosion resistance and the like are greatly deteriorated. Further, the method for controlling the conditions during plasma spraying requires complicated control operations such as changing the temperature for each spraying, and the crack extends to the entire thickness of the stabilized ZrO ₂ layer. The alloy layer is directly affected by the corrosive high temperature atmosphere, so that the heat shielding function inherent to the stabilized ZrO ₂ layer is not sufficiently exhibited, and the base material is likely to be thermally deteriorated.
[0007]
In view of the above circumstances, the present invention efficiently and reliably forms a heat-shielding ceramic film having a columnar structure due to cracks in the thickness direction on the surface of a heat-resistant component used under severe conditions, It is possible to exert a sufficient preventive effect against interfacial peeling due to impact, and provides a means that can avoid the direct influence of corrosive high temperature atmosphere to the base through the crack, and has excellent high temperature durability The purpose is to achieve long-life heat-resistant parts.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a method for forming a heat-shielding ceramic film according to the invention of claim 1 is a method for forming a ceramic film having a two-layer or three-layer structure on the surface of a workpiece. and upon form of an intermediate layer of a three-layer structure, by a ceramic material flop plasma sprayed on the surface while the laser irradiated to the workpiece surface of the spray zone, the intermediate layer of the upper layer and 3-layer structure of the two-layer structure A columnar structure is formed by cracking in the thickness direction . That is, according to this method, the plasma-sprayed ceramic material is heated to a high temperature by the laser beam simultaneously applied to the sprayed surface, the bonding force between the sprayed particles is increased, and the structure is densified. Along with the contraction when rapidly moving out of the laser irradiation area due to the movement, the film thickness direction cracks are formed in a mesh shape, and a columnar structure is formed by the stacking of the single layers in which the cracks are generated. In this case, since the upper layer of the two-layer structure and the intermediate layer of the three-layer structure are formed by plasma spraying under laser irradiation, the cracks constituting the columnar structure of the heat shielding ceramic film do not reach the ground surface. Thus, the base is not directly affected by the corrosive high temperature atmosphere through the cracks. Further, in the formation of this columnar structure , since laser irradiation is performed on the sprayed surface in a film forming process by normal plasma spraying, it is not necessary to add a separate process, and if laser irradiation is stopped, it is cracked as it is. Therefore, the crack depth and formation position can be arbitrarily set.
[0010]
In the invention of claim 2, in the method for forming a heat shielding ceramic film of claim 1, the ceramic material mainly composed of ZrO ₂ is used, so that the formed film exhibits an excellent heat shielding function. It will be a thing.
[0011]
According to a third aspect of the present invention, in the method for forming a heat-shielding ceramic film according to the first or second aspect, the plasma spraying is performed under laser irradiation with a laser power density of 100 to 350 W / mm ² on the irradiated surface. . In this case, since the laser power density is moderate, it is possible to form a columnar structure in a good state suitable for preventing interfacial peeling from the base on the thermal spray coating.
[0012]
According to a fourth aspect of the present invention, in the method for forming a heat-shielding ceramic film according to any one of the first to third aspects, plasma spraying is performed under laser irradiation by continuous oscillation of a YAG laser. It is easy to form a good columnar structure on the sprayed coating.
[0013]
The heat-resistant component according to the invention of claim 5 is provided with a heat-shielding ceramic coating having a two-layer or three-layer structure composed of a plasma sprayed layer on the surface of the component, and an upper layer of the two-layer structure or an intermediate layer of the three-layer structure of the ceramic coating. and it has a columnar structure by coating thickness direction of the crack formed by plasma spraying under laser irradiation of any of claims 1-4, the upper and lower layers of the lower layer or three-layer structure of the two-layer structure is plasma It is assumed to have a continuous structure formed only by thermal spraying. In this heat-resistant component, the columnar structure of the ceramic film prevents interfacial peeling due to thermal shock between the film and the base, and the cracks constituting the columnar structure do not reach the base surface. As a result, the entire substrate is excellent in high temperature durability and has a long life.
[0014]
According to a sixth aspect of the present invention, in the heat resistant component of the fifth aspect , the heat-shielding ceramic mainly comprising ZrO ₂ via a MCrAlY (M is Co and / or Ni) alloy layer on the surface of the Ni-base heat-resistant alloy base material. It is assumed that a film is formed. In this heat-resistant component, thermal properties such as high-temperature corrosion resistance, high-temperature oxidation resistance, and high-temperature durability are particularly superior to those of the base material, the base alloy layer, and the ceramic layer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for forming a heat-shielding ceramic film according to the present invention will be specifically described with reference to the drawings. In FIG. 1, 1 is a base material made of a heat-resistant alloy as a workpiece, 2 is a base alloy layer of high temperature corrosion resistance / high temperature oxidation resistance formed by plasma spraying on the base material 1, and 3 is a base alloy It is a heat shielding ceramic film being formed on the layer 2.
[0016]
As shown in FIG. 1, the heat shielding ceramic film 3 is formed by spraying a plasma spray P from a plasma spraying machine (not shown) at a fixed position while the base material 1 is advanced at a predetermined speed as indicated by an arrow a. However, a spot of a laser beam L emitted from a laser irradiation device (not shown) is simultaneously superimposed on the sprayed zone Z. As a result, the spray particles whose temperature has decreased during the flight process from the spray nozzle to the weld surface are reheated and melted in the spray zone Z, the bonding force between the melt particles increases, the structure becomes dense, and the spray zone Z As a result of this movement, the laser beam L is removed from the spot and rapidly cooled and solidified. As this solidification shrinkage occurs, cracks 4 in the film thickness direction are formed in a mesh shape as seen from the film surface as shown in FIG.
[0017]
However, although it depends on the spraying conditions, the diameter of the sprayed particles is around 50 μm, and the thickness of the single layer formed by one spraying (one pass) is 20 μm inside or outside, so that the ceramic coating 3 has the required thickness. However, if plasma spraying is continued under laser irradiation, cracks 4 due to solidification shrinkage of the single layer formed later will occur in the single layer underneath. Since it is easy to follow the pattern of the cracks 4..., Most of the cracks 4 extend in the thickness direction of the film.
[0018]
On the other hand, if only the laser irradiation is stopped in such a film forming mechanism, a film without cracks 4... Is formed by normal plasma spraying. Therefore, if the laser irradiation is stopped from the start of film formation on the base alloy layer 2 until the thickness of the sprayed layer reaches a certain level, and then the plasma spraying is performed while performing laser irradiation, FIG. Thus, the heat shielding ceramic film 3A having a two-layer structure of the upper layer 31a of the columnar structure and the lower layer 32a of the continuous structure is formed by the cracks 4. Further, if laser irradiation is further stopped on this two-layer structure and plasma spraying is performed, an intermediate layer 31b having a columnar structure is sandwiched between upper and lower layers 32a and 32b of the continuous structure as shown in FIG. 3B. A heat shielding ceramic coating 3B having a three-layer structure is formed.
[0019]
Thus, in the heat-resistant parts provided with the heat shielding ceramic coatings 3A and 3B having the two-layer structure and the three-layer structure, the former lower layer 32a and the latter intermediate layer 31b have a columnar structure. When subjected to thermal shock during use, even if there is a difference in expansion and contraction due to the difference in linear expansion coefficient between these coatings 3A and 3B, the base alloy layer 2 and the substrate 1, internal stress constitutes a crack that forms the columnar structure. 4 is absorbed and relaxed, and the interfacial delamination between the ceramic films 3A and 3B and the base alloy layer 2 is effectively suppressed, and the cracks 4 ... do not reach the base alloy layer 2, so that the base alloy layer 2 Is not directly affected by the corrosive high temperature atmosphere through the cracks 4 ..., and the ceramic coatings 3A and 3B can be formed thickly by plasma spraying to provide a sufficient heat shielding function. But sufficient high-temperature durability can be obtained.
[0020]
In order to ensure sufficient high-temperature durability of the heat-shielding ceramic film, the portion of the columnar structure formed by plasma spraying under laser irradiation is set to be 10% or more of the film thickness. It is good. However, in order to avoid the influence of the corrosive high temperature atmosphere on the base through the crack, it is preferable to form a continuous structure formed only by plasma spraying up to at least 7% of the film thickness from the base surface.
[0021]
Here, ZrO ₂ stabilized by adding MgO, CaO, Y ₂ O ₃ or the like is preferably used as the ceramic material used for the heat shielding

ceramic films

3, 3A, 3B. Further, as the heat-resistant alloy of the substrate 1, a Ni-based heat-resistant alloy such as Inconel is suitable. The base alloy layer 2 may be any material that is excellent in high-temperature corrosion resistance and high-temperature oxidation resistance, but an MCrAlY (M is Co and / or Ni) alloy is particularly recommended.
[0022]
Laser irradiation is suitably range laser power density on the irradiated surface is 100~350W / mm ^2, difficult to break 4 ... are formed at the same power density is less than ^{100W / mm 2, 350W / mm} 2 in the opposite If it exceeds, surface roughness of the film tends to occur. Further, the type of laser to be used is not particularly limited, but according to the laser beam by continuous oscillation of a YAG laser that is small and easy to handle, it is easy to form a good columnar structure on the sprayed coating due to its characteristics. Therefore, as shown in FIG. 1, when the laser beam L is overlapped on the sprayed area Z of the plasma spray P and the laser power density is set appropriately, the laser beam L deviates from the focal point to either deep or shallow. It is desirable to set the irradiation spot so that the irradiation spot substantially coincides with the sprayed area Z by being applied to the irradiation surface at a certain position.
[0023]
【Example】
Examples of the present invention will be specifically described below with reference examples. In these examples and reference examples, a gas turbine blade for power generation made of an Inconel alloy is used as a base material, and a CoNiCrAlY alloy layer having a thickness of 100 μm formed on the base material by low-pressure plasma spraying is used as a base, and a heat shielding ceramic is provided thereon. The coating 3 is formed by atmospheric plasma spraying or atmospheric plasma spraying under laser irradiation. Tables 1 and 2 show the plasma spraying conditions and laser irradiation conditions.
[0024]
[Table 1]

[0025]
[Table 2]

[0026]
Example 1
While holding the substrate having the CoNiCrAlY alloy layer formed on the robot, the plasma spraying machine and the laser irradiation device are fixed so that the spot of the laser beam L is superimposed on the spraying zone Z of the plasma spray P as shown in FIG. As the arrow a in FIG. 1 moves, the substrate 1 side is moved, and ZrO ₂ added with 8% by weight of Y ₂ O ₃ is used as a thermal spraying material, and 15-pass film formation is performed only by plasma spraying from the start of thermal spraying. With respect to, a 300 μm thick heat-shielding ceramic film was formed by performing 6-pass film formation while irradiating the laser beam L at a position 15 mm below the focal point (power density on the irradiated surface = 283 W / mm ² ).
[0027]
Reference example 1
A 300 μm thick heat-shielding ceramic film was formed in the same manner as in Example 1 except that the laser beam L was irradiated at a position 25 mm below the focal point (power density on the irradiated surface = 102 W / mm ² ).
[0028]
Example 2
From the start of thermal spraying, film formation of 8 passes is performed only by plasma spraying, then film formation of 6 passes is performed while irradiating the laser beam L at the same position as in Example 1, and film formation of 4 passes is performed only by plasma spraying. As a result, a 300 μm thick heat shielding ceramic film was formed.
[0029]
Reference example 2
From the start to the end of thermal spraying, the film was formed only by plasma spraying to form a 300 μm thick heat shielding ceramic film.
[0030]
Electron micrographs (× 150) of the cross-sectional structures of the heat-shielding ceramic coatings formed in Examples 1 and 2 and Reference Example 1, Example 1 is FIG. 4, Reference Example 1 is FIG. 5, and Example 2 is FIG. Respectively. As is clear from FIG. 4, the ceramic film formed in Example 1 has a two-layer structure of a clear columnar structure upper layer by cracks that are neatly aligned in the thickness direction and a lower layer of a continuous structure without cracks. There is no. On the other hand, the ceramic film formed in Reference Example 1 has almost no clear cracks at the top as shown in FIG. 5, and the intensity of the laser beam for forming the columnar structure is insufficient. I understand. On the other hand, FIG. 6 shows that the ceramic film formed in Example 2 has a three-layer structure in which an intermediate layer of a columnar structure is sandwiched between upper and lower layers of a continuous structure.
[0031]
[Thermal shock test]
Next, the gas turbine blades on which the heat shielding ceramic coating was formed in Examples 1 and 2 and Reference Examples 1 and 2 were heated to 990 ° C. in 4.5 minutes as shown in FIG. A thermal cycle of cooling to 60 ° C. in 5 minutes was regarded as one thermal shock, and this thermal shock was repeatedly applied, and the number of thermal shocks until the ceramic film was peeled was examined. The results are shown in Table 3 below.
[0032]
[Table 3]

[0033]
From the results in Table 3, the ceramic film of Reference Example 2 formed only by plasma spraying peeled off with only four thermal shocks, whereas the ceramic film of Reference Example 1 was insufficient to withstand thermal shock to some extent. In addition, it can be seen that the ceramic coatings of Examples 1 and 2 do not peel even by thermal shock of 1000 times or more, and the ceramic coating according to the present invention is extremely excellent in high temperature durability.
[0034]
【The invention's effect】
According to inventions of claims 1, a method of forming a ceramic coating having a two-layer or three-layer structure in the surface of the workpiece, upon formation of the intermediate layer of the upper layer and 3-layer structure of the two-layer structure, the spraying zone Since the ceramic material is plasma sprayed on the surface of the workpiece while irradiating the surface of the workpiece, the coating having a columnar structure that is unlikely to be peeled off by thermal shock is used as the upper layer of the two-layer structure and the intermediate layer of the three-layer structure. It can be reliably and easily formed at a low cost, and this coating can be provided on the surface of a heat-resistant component used in severe high temperature range to greatly improve high temperature durability. Further, in this method, it is possible to form a structure in which the cracks constituting the columnar structure do not reach the base surface and the corrosive high temperature atmosphere is prevented from reaching the base directly through the crack. Moreover, in the formation of the columnar structure, it is only necessary to irradiate the sprayed surface with a laser in a film forming process by normal plasma spraying, so there is no need to add a separate process for the formation of the columnar structure. In addition to high efficiency, it is possible to form a columnar structure at an arbitrary site and an arbitrary surface area in the film only by irradiating and stopping the laser, and to make the other a continuous structure only by plasma spraying.
[0036]
According to the invention of claim 2 , as the above-mentioned heat shielding ceramic film, one having particularly excellent heat shielding function can be formed.
[0037]
According to invention of Claim 3 , what has a columnar structure | tissue of the favorable state suitable for prevention of interface peeling with a foundation | substrate can be formed as said heat shielding ceramic membrane | film | coat.
[0038]
According to invention of Claim 4 , in the formation method of said heat shielding ceramic membrane | film | coat, there exists an advantage that a favorable columnar structure | tissue can be easily formed in the said membrane | film | coat.
[0039]
According to the invention of claim 5, as a heat-resistant parts, hardly occurs interfacial peeling due to thermal shock of the heat shield ceramic coating provided on the surface thereof, and the influence of the corrosive high temperature atmosphere without reaching directly to the substrate, it has been As a whole, a product having excellent durability at high temperature and long life is provided.
[0040]
According to the sixth aspect of the present invention, the heat-resistant component is particularly excellent in thermal properties such as high-temperature corrosion resistance, high-temperature oxidation resistance, and high-temperature durability.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing a method for forming a heat shielding ceramic film according to the present invention.
FIG. 2 is a perspective view of a single layer of a heat shielding ceramic film formed by a single plasma spraying process according to the same forming method.
FIGS. 3A and 3B show a heat-resistant component provided with a heat-shielding ceramic film formed by the same forming method, wherein FIG. 3A is a cross-sectional view of the heat-resistant component having the two-layer structure and FIG. 3B has the three-layer structure. It is sectional drawing of a heat-resistant component.
4 is an electron micrograph showing the cross-sectional structure of the heat-shielding ceramic film formed in Example 1. FIG.
5 is an electron micrograph showing the cross-sectional structure of the heat-shielding ceramic film formed in Reference Example 1. FIG.
6 is an electron micrograph showing the cross-sectional structure of the heat-shielding ceramic film formed in Example 2. FIG.
FIG. 7 is a thermal cycle diagram of a thermal shock test.
[Explanation of symbols]
1 Base material (workpiece)
2 Underlying alloy layers 3, 3A, 3B Heat shielding ceramic coating 31a Columnar structure upper layer 31b Continuous structure lower layer 32a Continuous structure upper layer 32b Columnar structure intermediate layer 32c Continuous structure lower layer 4 Crack P Plasma spray L Laser beam Z Thermal spray region

Claims

In the method of forming a ceramic film having a two-layer or three-layer structure on the surface of the workpiece, when forming the upper layer of the two-layer structure and the intermediate layer of the three-layer structure, the surface of the workpiece in the thermal spray region is irradiated with laser. by flop plasma spraying a ceramic material onto the surface, a method of forming the heat shield ceramic coating and forming a columnar structure by cracks in a thickness direction in the intermediate layer of the upper layer and 3-layer structure of the two-layer structure.

The method for forming a heat-shielding ceramic film according to claim 1, wherein a ceramic material mainly composed of ZrO ₂ is used.

Method of forming a heat shield ceramic coating according to claim 1 or 2 plasma spraying laser power density on the irradiated surface is performed by the laser irradiation under which the 100~350W / mm ^2.

The method for forming a heat shielding ceramic film according to any one of claims 1 to 3 , wherein the plasma spraying is performed under laser irradiation by continuous oscillation of a YAG laser.

The heat shielding ceramic coating of 2 layer or 3 layer structure which consists of a plasma sprayed layer is provided on the component surface, The upper layer of the 2 layer structure of this ceramic coating, or the intermediate | middle layer of 3 layer structure is any one of Claims 1-4 It has a columnar structure caused by cracks in the thickness direction of the film formed by plasma spraying under laser irradiation, and has a continuous structure in which the lower layer of the two-layer structure or the upper and lower layers of the three-layer structure is formed only by plasma spraying. Heat resistant parts.

6. The heat-resistant component according to claim 5, wherein the heat-shielding ceramic film mainly composed of ZrO ₂ is formed on the surface of a Ni-based heat-resistant alloy base material through an MCrAlY (M is Co and / or Ni) alloy layer.