JP4081305B2 - Coating material selection method and coating - Google Patents

Description

【００１１】
このようにして被膜が形成された複数（この試験例では２２枚）の試験片を、図２に概略図示する試験装置１０にそれぞれセットして試験を行った。同図において、１１はチャンバ１２を画定する試験槽、１３は試験槽１１内で回転可能に支持されていて、一方の表面（図２では左面）に試験片３ａ、３ｂ、３ｃが着脱可能に取り付けられるようになっている回転体、１４は回転体１３を回転させる電動モータ、１５及び１６は試験槽１１に取り付けられた圧力計及び温度計、１７はスラリータンク、１８はスラリータンク１７内のスラリーを導管１９を介してチャンバ１２内に送るスラリーポンプ、２０は水を導管２１を介して導管１９内に供給するポンプである。更に、２３ａないし２３ｅは導管に接続された開閉弁、２４は排出管２５に接続された開閉弁、２６はスラリータンク１７内を通って伸び水でスラリータンク内を冷却する熱交換管である。上記試験槽及び／又は回転板の試験片取り付け面は、回転ディスク１３が回転しているとき、スラリーが試験片の表面に所望の角度で当たるように作られている。
【００１２】
上記構成の試験装置において、回転ディスク１４の片面（図２で左面）に試験片３ａ、３ｂ、３ｃを取付け、これを試験槽１１内のスラリー中に没した状態でモータ１４により回転させる方法で実施した。試験槽内の圧力が０．１Ｍｐａ、温度が２５〜３０℃となるように調整した。実験条件は実際の河川濁水の状況に基づき、スラリー衝突速度が５５ｍ／ｓとなるように回転ディスクの回転速度を調節し、スラリー中の土砂濃度１ｗｔ．％とした。このような条件の実験を硬質の被膜が形成された上記各試験片につき試験を行い、損耗速度を求めた。その結果をグラフで表せば図３及び図４に示されるようになる。図３は被膜を構成する被膜のセラミックス硬質粒子の面積率と損耗速度との関係を示し、図４は被膜の硬質被膜の硬度と損耗速度との関係を示す。
本実験では硬質粒子であるセラミックス粒子の面積率が５〜５０％の範囲で実験を行った。その理由は、面積率が５０％を超えた場合には基材に対する被膜の接着力が低下して被膜に亀裂が多発するため、実用上無意味な範囲だからである。
【００１３】
図３から明らかなように、セラミックス硬質粒子面積率について着目すると、その値が２５〜５０％の範囲で、スラリーエロージョンによる損傷速度は小さくなり、ほぼ一定になる。従って、硬質粒子の面積率が好ましくは２５％ないし５０％の範囲となるように被膜を形成することによって、ポンプ部材の耐スラリーエロージョン性を向上させることができる。更に好ましくは３０％ないし４０％の範囲となる被膜を形成するとよい。
また、図４から明らかなように、被膜を構成する硬質被膜表面のビッカース硬度（測定荷重５００ｇ）について着目すると、その値が９００ｋｇ／ｍｍ²より小さいときはビッカース硬度が大きくなるにしたがって損耗速度が減少するが、略９００ｋｇ/ｍｍ²超えると損耗速度は略一定になることがわかる。このように、セラミックス硬質粒子面積率と硬質被膜硬度は、それぞれ耐スラリーエロージョン性にのみ影響を及ぼすことがわかる。
【００１４】
次に、耐キャビテーションエロージョン性に影響を及ぼす影響因子の評価について説明する。キャビテーションエロージョン試験は「エロージョン・コロージョンと利用技術、発行者：（株）ＩＰＣ」に記載されている回転円板法に準じて行った。ただし、円板、試験片等の寸法は異なる。
キャビテーションエロージョンについては、図５［Ａ］に示されるような円形（直径Ｄ＝２５ｍｍ、厚さＴ＝６ｍｍ）の平板状の試験片用の基板１′を多数作成し、前記図１の試験片と同じ種類の被膜材料を使用して同じように溶射し、図５［Ｂ］に示されるような、同じ被膜厚さを有する試験片３ａ′、３ｂ′及び３ｃ′をつくった。そしてそれらの試験片を図６及び図７に示す試験装置１０′にセットして行った。同図において、１１′はチャンバ１２′を画定する試験槽、１３′は試験槽１１′内で回転可能に支持されていて、一方の表面（図６では左面）に試験片３ａ、３ｂ、３ｃが着脱可能に取り付けられるようになっている回転体、１４′は回転体１３′を回転させる電動モータ、１７′は水タンク、１８′は水タンク１７′内の水を導管１９′を介して試験槽１１′内に送るポンプ、２０′は水を試験槽から水タンク１７′戻す導管である。回転体１３′には、試験片の取付け位置よりも回転体の回転方向に見て上流側に、所望の大きさ（本実施形態では直径１５ｍｍ）の円形穴１５′（非貫通穴）が形成されている。この穴１５′は、回転体が回転するときに回転体表面にキャビテーションを発生させるものである。
【００１５】
試験は、回転ディスク１３′の片面に前記試験片を取付け、これを水中に没した状態でモータ１４′により回転させ、回転体の回転によって発生したキャビテーションが試験片側に向かって流れるようにして行った。試験槽内の水圧は０．１Ｍｐａ、水温は１５℃に調整した。
【００１６】
上記試験により得た結果をグラフで表せば図８及び図９に示されるようになる。図８は単位面積あたりの空孔（平均径１μｍ以上）の周囲長合計と損耗速度の関係を示し、図９は空孔面積率と損耗速度の関係を示す。単位面積当りの空孔面積率及び周囲長合計は、硬質被膜表面の拡大写真をコンピュータに取り込み、デジタル画像処理を行い求めた。なお、硬質被膜表面の拡大写真をコンピュータに取り込むに先だって、表面を平坦面に沿って研磨して空孔部分（凹み部分）を分かり易くし、空孔の面積は硬質被膜表面の単位面積についてその凹み部分の面積及び凹み部分の周囲長を測定することによって求めた。
図８から明らかなように、硬質被膜表面の単位面積当りの空孔（平均径１μｍ以上）の周囲長合計増加するにしたがって被膜の損耗速度が増加することが明らかである。本発明では損耗速度が０．５ｍｍ³／ｈ以内に収まるように選定すると、周囲長合計が６００００μｍ／ｍｍ²以下となる。また、図９から明らかなように、硬質被膜表面の空孔面積率が増加すると被膜の損耗速度がそれに応じて増加することも明らかである。本発明では、空孔の周囲長合計の場合と同じように損耗速度が０．５ｍｍ³／ｈ以内に収まるように選定すると、空孔面積率は３％以下となる。このように、単位面積あたりの空孔（平均径１μｍ以上）の周囲長合計と空孔面積率は、それぞれ耐キャビテーションエロージョン性にのみ影響を及ぼす。なお、損耗速度の上限を０．５ｍｍ³／ｈより小さい値（例えば０．２ｍｍ³／ｈ）にしようとすれば、空孔面積率も小さな値（例えば２％）となる。
【００１７】
本発明による被膜で耐スラリーエロージョン化及び耐キャビテーションエロジョン化を図った流体機械用の構成部材の一例としてポンプのランナすなわち羽根車３０が図１０で断面図で示されている。
図１０において、羽根車３０は、回転軸を受ける軸穴３１が形成されたハブ３２と、そのハブ３２から半径方向外側に放射上に広がる円板状の主板３３と、主板３３から軸方向（図２において上下方向）に隔てられた環状の側板３４と、主板３３と側板３４との間において円周方向（軸穴の軸線Ｏ−Ｏ回りの円周方向）に等間隔に隔てて配置され所望の曲面に沿って湾曲して側板及び主板と一体的に形成された複数の翼３５とで構成されていて、主板３３、側板３４及び翼３５により流体の流れる流路３６を画定している。流路３６の半径方向内側の部分３７が入口部となり、半径方向外側の部分３８が出口部となる。また、環状の側板３４は、円周方向内側の軸方向に伸びる部分３４ａと、半径方向外側に伸びる部分３４ｂとを有し、軸方向伸長部分３４ａによって羽根車３０の入口３９を画定している。このような羽根車３０を回転させて流体を送り出す場合、例えば、羽根車を土砂を含む水中で回転させると、水中の土砂の粒子が羽根車３０の表面、特に羽根車３０内の流路３６を画定する主板３３の内面４１、側板３４の内面４２及び翼３５の両面、すなわち圧力面４３、負圧面４４に当たってこれを擦り、それらの表面が摩擦により極端に摩耗することになる。
【００１８】
そこで、羽根車３０の上記流路３６を画成する内面４１及び４２、圧力面４３及び負圧面４４、入口３９の内面４５、側板３４の外側面４６及び主板３３の裏面４７のうち所望する面に、上記溶射法ＡないしＣのうち適当な溶射法を適宜選んで前述の耐スラリーエロージョン溶射被膜を形成する。この場合、溶射を行う面の条件、溶射法の施工条件等を考慮して一つの羽根車に対して溶射する場所により異なる溶射方法を採用することも可能である。
【００１９】
上記のように耐スラリーエロージョン溶射被膜形成された本発明の羽根車３０は、水車或いはポンプのような流体機械に使用される。図１１において、このような流体機械の一例として立形ポンプ５０が断面で示されている。同図において、ポンプ５０は、本発明による羽根車３０を収容するポンプ室５２を画成するケーシング５１と、軸線を鉛直にして配置されていて下端に羽根車３０が固定された主軸５７と、ケーシングの上方に取り付けられたていて主軸５７をケーシングに関して回転自在に支持する主軸受け５８と、ケーシング５１と主軸５７との間からの流体の漏れを防止するシール装置５９と、を備えている。ケーシング５１は管状の支持台６０の上に公知の方法で固定されている。ケーシング５１は、上側の円盤状の端板５３と、渦巻き状の出口室５５を画成するケーシング本体５４と、管状のカバー５６とを備えている。カバー５６の下端には筒状の吸出し管６１が接続されている。
上記ポンプにおいて、主軸３７を回転させることによってその下端に固定された羽根車３０を回転させると、流体が吸出し管６１内で矢印Ｘで示されるように羽根車の入口３９に吸い込まれ、羽根車３０の流路３６を通って出口３８側から半径方向に押し出され、出口室５５内に流入する。出口室内の流体は、図示しない出口から吐き出される。
【００２０】
【発明の効果】
本発明によれば次のような効果を奏することが可能である。
（イ）耐スラリーエロージョン性のみ、あるいは耐キャビテーションエロージョン性のみに、影響をおよぼす材料因子を明らかにし、各々の因子に実質的に従属関係がないことを見出したことで、各硬質被膜ごとの試験片などによる評価試験が不要となり、被膜の材料選定に時間とコストの大幅な節約となる。
（ロ）河川水等に代表される、土砂と水が主成分であるスラリーによるエロージョンに対して、硬質被膜の表面の硬質粒子の面積率又はビッカース硬さを所望の範囲にし、かつ被膜表面の単位面積当りの空孔の周囲長合計又は空孔面積率を所望の範囲にすることによって、高い耐スラリーエロージョン性及び耐キャビテーションエロージョン性を有する被膜の被膜を溶射法により容易に形成できる。
（ハ）土砂を含む水を扱う流体機械の構成部材の耐スラリーエロージョン特性及び耐キャビテーションエロージョン特性を向上でき、流体機械の寿命を長くすることが可能である。
【図面の簡単な説明】
【図１】スラリーエロージョン試験用の試験片及び試験片用の基板の斜視図である。
【図２】本実施例で使用する耐スラリーエロージョン性を評価する試験装置の概略構成図である。
【図３】試験結果を示すグラフ図である。
【図４】試験結果を示すグラフ図である。
【図５】キャビテーションエロージョン試験用の試験片及び試験片用の基板の斜視図である。
【図６】本実施例で使用する耐キャビテーションエロージョン性を評価する試験装置の概略構成図である。
【図７】図６に示される装置の回転体の一部分の平面図である。
【図８】試験結果を示すグラフ図である。
【図９】試験結果を示すグラフ図である。
【図１０】本発明の被膜が形成される羽根車の一例を示す断面図である。
【図１１】図１０の羽根車を備えるポンプの断面図である。
【符号の説明】
１、１′ 基板 ２ａ、２ｂ、２ｃ 被膜
２ａ′、２ｂ′、２ｃ′ 被膜 ３ａ、３ｂ、３ｃ 試験片
３ａ′、３ｂ′、３ｃ′ 試験片
３０ 羽根車 ３２ ハブ
３５ 翼 ５０ ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an erosion-resistant coating and a method for selecting the material thereof, and more specifically, a method for selecting a material for an erosion-resistant coating having both slurry erosion resistance and cavitation erosion resistance and the selection method. More particularly, the present invention relates to an impeller coated with such a coating and a fluid machine having the impeller.
[0002]
[Prior art]
In a fluid machine such as a pump or a water wheel for handling liquid such as water containing granular earth and sand, a rotating member such as a runner that operates in the fluid, that is, an impeller, or a component that forms a fluid flow path has a surface in contact with the fluid. Therefore, it is necessary to use a material excellent in slurry erosion resistance in order to prevent abrasion of the steel. However, such a material excellent in slurry erosion resistance is not only expensive, but also has other problems of lacking mechanical strength when used alone, usually considering performance, cost, repair, etc. A hard spray coating is deposited to a desired thickness on the surface of the base material constituting the constituent member, and such a base material is protected from abrasion. As a material for such a hard sprayed coating, a cermet material which is a composite material of ceramics and metal is often used conventionally.
On the other hand, it is necessary to take into account cavitation erosion generated by rotation in a rotating member of a fluid machine that rotates in water, for example, an impeller, and a coating that covers the surface of such a rotating member includes a material that can withstand cavitation erosion. Required.
[0003]
[Problems to be solved by the invention]
By the way, until now, it is difficult to say that the selection of materials for hard coatings used for such purposes has been performed according to clear selection criteria for slurry erosion resistance and cavitation erosion resistance. At present, materials are selected based on this.
Conventionally, since harder materials generally have better slurry erosion resistance, materials have been developed in the direction of improving hardness by incorporating ceramic hard particles as much as possible. However, when the content of the ceramic hard particles is increased, the content of the metal portion that acts as a binder is decreased, so that the workability is deteriorated and cracks are easily generated. In addition, hard coatings may have uneven ceramic hard particles depending on the type of material, making it difficult to accurately measure the hardness.
[0004]
Furthermore, regarding the influencing factors related to materials that affect slurry erosion resistance and influencing factors related to materials that affect cavitation erosion resistance, it has not been confirmed how they relate to each other. No way has been sought.
[0005]
Accordingly, an object of the present invention is to clarify the influencing factors relating to the material affecting the slurry erosion resistance and the influencing factors relating to the material affecting the cavitation erosion resistance, and to provide a rational material selection method for the erosion resistant coating. Is to provide.
Another object of the present invention is to use the ceramic particle area ratio or Vickers hardness of the coating surface for slurry erosion resistance, and for the cavitation erosion resistance, the total perimeter of pores per unit area of the coating surface or The object of the present invention is to provide a method for selecting a material for a coating film to be evaluated using a void area ratio.
Another object of the present invention is to provide a coating for thermal spraying composed of a material selected by the above selection method.
Still another object of the present invention is to provide an impeller coated with the coating and a fluid machine having such an impeller.
[0006]
[Means for Solving the Problems]
One invention of the present application is a method for selecting a coating material containing ceramics and a metal for coating a substrate surface using a thermal spraying method,
It is characterized in that a material factor affecting only the slurry erosion resistance and a material factor affecting only the cavitation erosion resistance are independently evaluated and selected.
In the method of selecting a coating material according to the above invention, the ceramic particle area ratio on the coating surface is used for the slurry erosion resistance, and the perimeter of the pores (average diameter of 1 μm or more) per unit area on the coating surface is used for the cavitation erosion resistance. Even if the total is evaluated, the Vickers hardness of the coating surface is used for the slurry erosion resistance, and the total perimeter of pores (average diameter of 1 μm or more) per unit area of the coating surface is used for the cavitation erosion resistance. Even if it is evaluated, the ceramic particle area ratio on the coating surface is used for the slurry erosion resistance, and the void area ratio on the coating surface is used for the cavitation erosion resistance, or the slurry erosion resistance is Using the Vickers hardness of the coating surface, the cavitation erosion resistance is the void area ratio of the coating surface. You may evaluate using.
[0007]
Another invention of the present application is a coating composed of ceramic particles containing at least one of a metal carbide and a metal oxide, and a metal, the ceramic particle area ratio of the coating surface being 25 to 50%, and the coating surface This is characterized in that the total perimeter of pores (average diameter of 1 μm or more) per unit area is 60000 μm / mm ² or less.
Another invention of the present application is a coating composed of ceramic particles containing at least one of a metal carbide and a metal oxide, and a metal, wherein the Vickers hardness of the coating surface is 900 kg / mm ² or more, and It is characterized in that the total perimeter of pores (average diameter 1 μm or more) per unit area is 60000 μm / mm ² or less.
Still another invention of the present application is a coating composed of ceramic particles containing at least one kind of metal carbide and metal oxide, and a metal, wherein the ceramic particle area ratio on the coating surface is 25 to 50%, and the coating It is characterized in that the surface pore area ratio is 3% or less.
Still another invention of the present application is a coating composed of ceramic particles containing at least one of a metal carbide and a metal oxide, and a metal, wherein the Vickers hardness of the coating surface is 900 kg / mm ² or more, and the coating surface It is characterized in that the hole area ratio is 3% or less.
[0008]
Yet another invention of the present application is an impeller comprising a hub and a plurality of wings attached circumferentially around the hub.
It is characterized in that at least a part of the surface of the impeller is coated with the coating according to any one of claims 6 to 9 by a thermal spraying method.
A fluid machine according to still another invention of the present application includes an impeller comprising a hub and a plurality of blades attached to the circumference of the hub in a circumferential direction;
A casing defining a chamber for rotatably housing the impeller;
And at least a part of the surface of the impeller is characterized in that the coating according to any one of claims 6 to 9 is coated by a thermal spraying method.
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
First, the evaluation of influential factors affecting the slurry erosion resistance will be described. First, a large number of substrates 1 for flat test pieces having a sector shape (radius R = 180 mm, thickness T = 6 mm) as shown in FIG. On the other hand, (A) Seven types of coating materials are prepared as materials for high-speed flame spraying, and each of the seven types of coating materials is sprayed separately on each substrate 1 and has a thickness t = 500 μm. A coating 2a having seven types of compositions A1 to A7 shown in Table 1 was formed, and a test piece 3a (FIG. 1 [B]) was formed. In addition, (B) 10 types of coating materials are prepared as materials for flame spraying, and the 10 types of coating materials are sprayed separately on each substrate 1, and the thickness t = 500 μm is shown in Table 1. Each of the coatings 2b having 10 kinds of compositions B1 to B10 shown in the drawing was formed, and a test piece 3b (FIG. 1 [B]) was produced. Then, the coating film was heat-treated to attempt densification of the coating structure. Further, (C) five types of coating materials are prepared as materials for arc spraying, and each of the five types of coating materials is sprayed separately on each substrate 1, and the thickness t = 500 μm is shown in Table 1. Films 2c having five types of compositions C1 to C5 shown in Fig. 1 were formed, respectively, to produce a test piece 3c (Fig. 1 [B]). In addition, even if it is the same composition in a table | surface, a carbide | carbonized_material average particle diameter, spraying conditions, etc. differ, and it is a film from which all characteristics differ. Moreover, the notation of Cr _m C _n in the table represents a mixture of chromium carbides such as Cr ₃ C ₂ , Cr ₇ C ₃ , and Cr ₂₃ C ₆ .
[0010]
[Table 1]

[0011]
A plurality of test pieces (22 in this test example) on which the coating film was formed in this way were set in the test apparatus 10 schematically shown in FIG. In the figure, 11 is a test tank that defines a chamber 12, 13 is rotatably supported in the test tank 11, and test pieces 3a, 3b, and 3c can be attached to and detached from one surface (left side in FIG. 2). Rotating body to be attached, 14 is an electric motor for rotating the rotating body 13, 15 and 16 are pressure gauges and thermometers attached to the test tank 11, 17 is a slurry tank, 18 is a slurry tank 17 A slurry pump 20 for feeding the slurry into the chamber 12 through the conduit 19, and 20 is a pump for supplying water into the conduit 19 through the conduit 21. Further, 23a to 23e are open / close valves connected to the conduit, 24 is an open / close valve connected to the discharge pipe 25, and 26 is a heat exchange pipe extending through the slurry tank 17 and cooling the slurry tank with water. The test piece mounting surface of the test tank and / or the rotating plate is formed so that the slurry hits the surface of the test piece at a desired angle when the rotating disk 13 is rotating.
[0012]
In the test apparatus having the above configuration, the test pieces 3a, 3b, and 3c are attached to one side (left side in FIG. 2) of the rotating disk 14, and this is rotated by the motor 14 while being immersed in the slurry in the test tank 11. Carried out. It adjusted so that the pressure in a test tank might be 0.1 Mpa and temperature might be 25-30 degreeC. The experimental conditions were based on the actual situation of river muddy water. The rotational speed of the rotating disk was adjusted so that the slurry collision speed was 55 m / s, and the sediment concentration in the slurry was 1 wt. %. An experiment under such conditions was performed on each of the above test pieces on which a hard film was formed, and the wear rate was obtained. The results are shown in graphs as shown in FIG. 3 and FIG. FIG. 3 shows the relationship between the area ratio of the ceramic hard particles of the coating film and the wear rate, and FIG. 4 shows the relationship between the hardness of the hard coating film and the wear rate.
In this experiment, the experiment was performed in a range where the area ratio of ceramic particles as hard particles was 5 to 50%. The reason is that when the area ratio exceeds 50%, the adhesive strength of the coating film to the substrate is reduced and the coating film is frequently cracked, which is a practically meaningless range.
[0013]
As is apparent from FIG. 3, when attention is paid to the ceramic hard particle area ratio, the damage rate due to slurry erosion decreases and becomes almost constant in the range of 25 to 50%. Therefore, the slurry erosion resistance of the pump member can be improved by forming the coating so that the area ratio of the hard particles is preferably in the range of 25% to 50%. More preferably, a film having a range of 30% to 40% may be formed.
As is apparent from FIG. 4, when attention is paid to the Vickers hardness (measurement load 500 g) of the hard coating surface constituting the coating, when the value is smaller than 900 kg / mm ^{2, the} wear rate increases as the Vickers hardness increases. Although it decreases, it can be seen that the wear rate becomes substantially constant when it exceeds approximately 900 kg / mm ² . Thus, it can be seen that the ceramic hard particle area ratio and the hard coating hardness only affect the slurry erosion resistance.
[0014]
Next, evaluation of influential factors that affect cavitation erosion resistance will be described. The cavitation erosion test was performed according to the rotating disk method described in “Erosion Corrosion and Utilization Technology, Issuer: IPC Co., Ltd.”. However, the dimensions of the discs and test pieces are different.
For cavitation erosion, a large number of circular plate (diameter D = 25 mm, thickness T = 6 mm) flat plate-like test pieces 1 ′ as shown in FIG. The same kind of coating material was used for the same thermal spraying to produce test pieces 3a ′, 3b ′ and 3c ′ having the same film thickness as shown in FIG. 5B. These test pieces were set in a test apparatus 10 'shown in FIGS. In this figure, 11 'is a test tank defining a chamber 12', 13 'is rotatably supported in the test tank 11', and test pieces 3a, 3b, 3c are mounted on one surface (left side in FIG. 6). Rotating body 14 is removably mounted, 14 'is an electric motor for rotating the rotating body 13', 17 'is a water tank, 18' is water in the water tank 17 'via a conduit 19'. A pump 20 'for feeding water into the test tank 11' is a conduit for returning water from the test tank to the water tank 17 '. A circular hole 15 ′ (non-through hole) having a desired size (a diameter of 15 mm in the present embodiment) is formed in the rotating body 13 ′ on the upstream side in the rotation direction of the rotating body from the mounting position of the test piece. Has been. This hole 15 'is for generating cavitation on the surface of the rotating body when the rotating body rotates.
[0015]
The test was performed by attaching the test piece to one side of the rotating disk 13 'and rotating it with the motor 14' while immersed in water so that cavitation generated by the rotation of the rotating body flows toward the test piece side. It was. The water pressure in the test tank was adjusted to 0.1 MPa and the water temperature to 15 ° C.
[0016]
If the result obtained by the said test is represented with a graph, it will come to be shown by FIG.8 and FIG.9. FIG. 8 shows the relationship between the total perimeter of holes (average diameter of 1 μm or more) per unit area and the wear rate, and FIG. 9 shows the relationship between the hole area ratio and the wear rate. The hole area ratio per unit area and the total perimeter were obtained by taking an enlarged photograph of the hard coating surface into a computer and performing digital image processing. Before taking an enlarged photograph of the hard coating surface into the computer, the surface is polished along a flat surface to make the pores (dents) easy to understand. It calculated | required by measuring the area of a dent part, and the perimeter of a dent part.
As is apparent from FIG. 8, it is clear that the wear rate of the coating increases as the total perimeter of the pores (average diameter of 1 μm or more) per unit area of the hard coating surface increases. In the present invention, if the wear rate is selected to be within 0.5 mm ³ / h, the total perimeter becomes 60000 μm / mm ² or less. Further, as is clear from FIG. 9, it is clear that the wear rate of the coating increases correspondingly when the pore area ratio on the surface of the hard coating increases. In the present invention, when the wear rate is selected to be within 0.5 mm ³ / h as in the case of the total perimeter of the holes, the hole area ratio is 3% or less. As described above, the total perimeter of the pores per unit area (average diameter of 1 μm or more) and the pore area ratio affect only the cavitation erosion resistance. If the upper limit of the wear rate is set to a value smaller than 0.5 mm ³ / h (for example, 0.2 mm ³ / h), the hole area ratio also becomes a small value (for example, 2%).
[0017]
FIG. 10 is a cross-sectional view of a pump runner or impeller 30 as an example of a component for a fluid machine that is made to have slurry erosion resistance and cavitation erosion resistance with the coating according to the present invention.
In FIG. 10, the impeller 30 includes a hub 32 having a shaft hole 31 for receiving a rotation shaft, a disk-shaped main plate 33 radiating radially outward from the hub 32, and an axial direction from the main plate 33 ( 2 are arranged at equal intervals in the circumferential direction (circumferential direction around the axis OO of the shaft hole) between the annular side plate 34 and the main plate 33 and the side plate 34 separated in the vertical direction in FIG. It comprises a plurality of blades 35 that are curved along a desired curved surface and are integrally formed with the side plate and the main plate. The main plate 33, the side plate 34, and the blades 35 define a flow path 36 through which fluid flows. . A radially inner portion 37 of the flow path 36 serves as an inlet portion, and a radially outer portion 38 serves as an outlet portion. The annular side plate 34 has a portion 34a extending in the axial direction on the inner side in the circumferential direction and a portion 34b extending outward in the radial direction, and an inlet 39 of the impeller 30 is defined by the axially extending portion 34a. . When the impeller 30 is rotated and the fluid is sent out, for example, when the impeller is rotated in water containing earth and sand, particles of the earth and sand in the water, the flow path 36 in the impeller 30, particularly the impeller 30. The inner surface 41 of the main plate 33, the inner surface 42 of the side plate 34, and both surfaces of the blades 35, that is, the pressure surface 43 and the negative pressure surface 44 are rubbed against each other, and these surfaces are extremely worn by friction.
[0018]
Therefore, a desired surface among the inner surfaces 41 and 42, the pressure surface 43 and the negative pressure surface 44, the inner surface 45 of the inlet 39, the outer surface 46 of the side plate 34, and the rear surface 47 of the main plate 33 that define the flow path 36 of the impeller 30. Further, an appropriate thermal spraying method is appropriately selected from the thermal spraying methods A to C to form the above-mentioned slurry erosion-resistant thermal spray coating. In this case, it is also possible to adopt different spraying methods depending on the location of spraying on one impeller in consideration of the conditions of the surface to be sprayed, the construction conditions of the spraying method, and the like.
[0019]
The impeller 30 of the present invention having the slurry erosion sprayed coating formed thereon as described above is used in a fluid machine such as a water wheel or a pump. In FIG. 11, a vertical pump 50 is shown in cross section as an example of such a fluid machine. In the figure, a pump 50 includes a casing 51 that defines a pump chamber 52 that houses the impeller 30 according to the present invention, a main shaft 57 that is arranged with the axis line vertical and the impeller 30 is fixed to the lower end, A main bearing 58 attached above the casing and rotatably supporting the main shaft 57 with respect to the casing, and a seal device 59 for preventing leakage of fluid from between the casing 51 and the main shaft 57 are provided. The casing 51 is fixed on the tubular support base 60 by a known method. The casing 51 includes an upper disk-shaped end plate 53, a casing body 54 that defines a spiral outlet chamber 55, and a tubular cover 56. A cylindrical suction pipe 61 is connected to the lower end of the cover 56.
In the pump, when the impeller 30 fixed to the lower end of the main shaft 37 is rotated, the fluid is sucked into the inlet 39 of the impeller as indicated by the arrow X in the suction pipe 61, and the impeller It is pushed out from the outlet 38 side through the 30 flow paths 36 in the radial direction and flows into the outlet chamber 55. The fluid in the outlet chamber is discharged from an outlet (not shown).
[0020]
【The invention's effect】
According to the present invention, the following effects can be obtained.
(B) By clarifying material factors that affect only slurry erosion resistance or only cavitation erosion resistance, and finding that there is virtually no dependency on each factor, testing for each hard coating An evaluation test with a piece or the like becomes unnecessary, and the time and cost can be saved greatly in selecting the material of the coating.
(B) With respect to erosion caused by slurry consisting mainly of sediment and water, such as river water, the hard particle surface area ratio or Vickers hardness of the hard coating surface is set to a desired range, and the coating surface By setting the total perimeter of the pores per unit area or the pore area ratio within a desired range, a coating film having high slurry erosion resistance and cavitation erosion resistance can be easily formed by a thermal spraying method.
(C) It is possible to improve the slurry erosion resistance and cavitation erosion characteristics of components of a fluid machine that handles water containing earth and sand, and to extend the life of the fluid machine.
[Brief description of the drawings]
FIG. 1 is a perspective view of a test piece for a slurry erosion test and a substrate for the test piece.
FIG. 2 is a schematic configuration diagram of a test apparatus for evaluating slurry erosion resistance used in this example.
FIG. 3 is a graph showing test results.
FIG. 4 is a graph showing test results.
FIG. 5 is a perspective view of a test piece for a cavitation erosion test and a substrate for the test piece.
FIG. 6 is a schematic configuration diagram of a test apparatus for evaluating cavitation erosion resistance used in this example.
7 is a plan view of a part of the rotating body of the apparatus shown in FIG. 6. FIG.
FIG. 8 is a graph showing test results.
FIG. 9 is a graph showing test results.
FIG. 10 is a cross-sectional view showing an example of an impeller on which a coating film of the present invention is formed.
11 is a cross-sectional view of a pump including the impeller of FIG.
[Explanation of symbols]
1, 1 'substrate 2a, 2b, 2c coating 2a', 2b ', 2c' coating 3a, 3b, 3c test piece 3a ', 3b', 3c 'test piece 30 impeller 32 hub 35 blade 50 pump

Claims (6)

In the method of selecting a coating material containing ceramics and metal for coating the substrate surface using a thermal spraying method,
Only the slurry erosion resistance is evaluated based on whether the ceramic particle area ratio on the coating surface is 25 to 50%,
Only the cavitation erosion resistance was evaluated based on whether or not the total peripheral length of the pores on the coating surface was 60000 μm / mm ² or less ,
A method for selecting a material for a film, comprising selecting a material having a ceramic particle area ratio of 25 to 50% on the surface of the film and a total perimeter of pores on the surface of the film being 60000 μm / mm ² or less . In the method of selecting a coating material containing ceramics and metal for coating the substrate surface using a thermal spraying method,
Only the slurry erosion resistance is evaluated based on whether the Vickers hardness of the coating surface is 900 kg / mm ² or more,
Only the cavitation erosion resistance was evaluated based on whether or not the total peripheral length of the pores on the coating surface was 60000 μm / mm ² or less ,
A method for selecting a material for a film, wherein a material having a Vickers hardness of 900 kg / mm ² or more on the surface of the film and a total perimeter of pores on the surface of the film being 60000 μm / mm ² or less is selected. In a coating composed of ceramic particles containing at least one of metal carbide and metal oxide, and a metal,
The ceramic particle area ratio on the surface of the coating is 25 to 50%, and the wear rate due to slurry erosion is 1 μm / h or less,
A coating for thermal spraying, characterized in that the total perimeter of pores on the surface of the coating is 60000 μm / mm ² or less and the wear rate due to cavitation erosion is 0.5 mm ³ / h or less. In a coating composed of ceramic particles containing at least one of metal carbide and metal oxide, and a metal,
The Vickers hardness of the coating surface is 900 kg / mm ² or more, and the wear rate due to slurry erosion is 1 μm / h or less,
A coating for thermal spraying, characterized in that the total perimeter of pores on the surface of the coating is 60000 μm / mm ² or less and the wear rate due to cavitation erosion is 0.5 mm ³ / h or less. In an impeller comprising a hub and a plurality of wings circumferentially spaced around the hub,
An impeller wherein at least part of the surface of the impeller is coated with the coating according to claim 3 or 4 by a thermal spraying method. An impeller comprising a hub and a plurality of wings circumferentially spaced around the hub;
A casing defining a chamber for rotatably housing the impeller;
With
5. A fluid machine, wherein at least a part of a surface of the impeller is coated with the coating according to claim 3 or 4 by a thermal spraying method.

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