JP5083857B2 - Covering member and manufacturing method thereof - Google Patents

Covering member and manufacturing method thereof Download PDF

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JP5083857B2
JP5083857B2 JP2006206456A JP2006206456A JP5083857B2 JP 5083857 B2 JP5083857 B2 JP 5083857B2 JP 2006206456 A JP2006206456 A JP 2006206456A JP 2006206456 A JP2006206456 A JP 2006206456A JP 5083857 B2 JP5083857 B2 JP 5083857B2
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nitriding
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stainless steel
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富美男 清水
新太郎 五十嵐
憲一 鈴木
英男 太刀川
和之 中西
義雄 加藤
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Toyota Central R&D Labs Inc
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Description

本発明は、ステンレス鋼からなる基材の表面に被膜をもつ被覆部材およびその製造方法に関し、特に、オーステナイト系ステンレス鋼からなる基材の表面処理に関する。   The present invention relates to a covering member having a coating on the surface of a base material made of stainless steel and a method for producing the same, and more particularly to surface treatment of a base material made of austenitic stainless steel.

ステンレス鋼は、Crを約12mass%以上含む低炭素の鉄基合金である。ステンレス鋼は、表面に安定な不動態被膜を形成して安定化するため、優れた耐食性を示す。不動態被膜の形成に深く関わる合金元素はクロム(Cr)であり、Cr濃度が12mass%を超えると急激に耐食性が向上し、環境によってはほとんど腐食しなくなる。ステンレス鋼のなかでも、オーステナイト系ステンレス鋼は、高温および低温における化学的・機械的性質が安定であるため、建築内外装材、車両、各種化学プラント等、極めて広範囲に用いられている。しかしながら、オーステナイト系ステンレス鋼であっても、使用する環境によっては腐食するため、さらなる耐食性の向上が求められている。ステンレス鋼の耐食性を向上させる方法の一例として、ステンレス鋼の表面に耐食性の高い非晶質炭素(ダイヤモンドライクカーボン:DLC)膜等の被膜を形成することが挙げられる。   Stainless steel is a low-carbon iron-based alloy containing about 12 mass% or more of Cr. Stainless steel exhibits excellent corrosion resistance because it stabilizes by forming a stable passive film on the surface. The alloy element deeply involved in the formation of the passive film is chromium (Cr), and when the Cr concentration exceeds 12 mass%, the corrosion resistance is rapidly improved, and it hardly corrodes depending on the environment. Among stainless steels, austenitic stainless steels are used in a very wide range of materials such as interior and exterior materials for buildings, vehicles, and various chemical plants because of their stable chemical and mechanical properties at high and low temperatures. However, even austenitic stainless steel corrodes depending on the environment in which it is used, and therefore further improvement in corrosion resistance is required. One example of a method for improving the corrosion resistance of stainless steel is to form a coating such as an amorphous carbon (diamond-like carbon: DLC) film having high corrosion resistance on the surface of stainless steel.

ステンレス鋼からなる基材の表面に被膜を形成する場合には、基材と被膜との密着性を高めるために、基材に窒化処理が行われる。たとえば、特許文献1には、オーステナイト系ステンレス鋼製の基材を転造加工してから窒化処理を行い、その表面にDLC膜を形成した塗工用ロッドが開示されている。ところが、このロッドを腐食が発生しやすい環境下で使用すると、未処理のオーステナイト系ステンレス鋼が腐食しないような使用環境であっても、DLC膜が剥離する。これは、窒化された基材に腐食が発生し、基材とDLC膜との界面で錆が体積膨張してDLC膜を浮き上がらせたためである。すなわち、基材を窒化する条件によっては、オーステナイト系ステンレス鋼の耐食性は低下する。   When forming a film on the surface of a base material made of stainless steel, the base material is subjected to nitriding treatment in order to improve the adhesion between the base material and the film. For example, Patent Document 1 discloses a coating rod in which a base material made of austenitic stainless steel is rolled and then subjected to nitriding to form a DLC film on the surface thereof. However, when this rod is used in an environment where corrosion is likely to occur, the DLC film peels even in an environment where untreated austenitic stainless steel does not corrode. This is because corrosion occurred in the nitrided base material, and rust volume-expanded at the interface between the base material and the DLC film to lift the DLC film. That is, depending on the conditions for nitriding the substrate, the corrosion resistance of the austenitic stainless steel decreases.

そこで、特許文献2には、耐食性を向上させるために、オーステナイト系ステンレス鋼を固溶化熱処理した後、表面を研削し、被処理面にオーステナイト組織が現れるようにした状態で浸炭処理および窒化処理して得られるオーステナイト系ステンレス鋼の表面構造が開示されている。また、非特許文献1には、オーステナイト系ステンレス鋼を窒化処理して、耐食性に優れる「S相」を表面に生成させる条件として、S相中にCrの化合物が析出しないように、450℃以下の低温で窒化を行うことが記載されている。
特開2004−344759号公報 特開2005−272978号公報 市井、外3名,「オーステナイト系ステンレス鋼の低温窒化」,表面技術,2003年,第54巻,第3号,p.28−31
Therefore, in Patent Document 2, in order to improve corrosion resistance, after austenitic stainless steel is subjected to solution heat treatment, the surface is ground, and carburizing treatment and nitriding treatment are performed in a state where the austenite structure appears on the surface to be treated. The surface structure of the austenitic stainless steel obtained in this way is disclosed. Further, Non-Patent Document 1 describes that as a condition for nitriding austenitic stainless steel to generate an “S phase” having excellent corrosion resistance on the surface, 450 ° C. or lower so that a Cr compound does not precipitate in the S phase. It is described that nitriding is performed at a low temperature.
JP 2004-344759 A JP 2005-272978 A Ichii, et al., “Low-temperature nitriding of austenitic stainless steel”, Surface Technology, 2003, Vol. 54, No. 3, p. 28-31

本発明者等は、オーステナイト系ステンレス鋼を加工する際に生成する加工誘起マルテンサイトに注目した。特許文献1および特許文献2では、オーステナイト系ステンレス鋼を転造加工したり研削したりすることで、加工誘起マルテンサイトが生成される。本発明者等は、後に詳説するように、マルテンサイト組織の存在により窒化処理後のステンレス鋼の耐食性が低下すると考えた。そのため、非特許文献1に記載のように、450℃以下の低温で窒化を行ったとしても、窒化されるオーステナイト系ステンレス鋼の状態によっては、窒化処理後の耐食性は低下するという問題がある。   The present inventors have paid attention to the processing-induced martensite generated when processing austenitic stainless steel. In Patent Document 1 and Patent Document 2, work-induced martensite is generated by rolling or grinding austenitic stainless steel. As will be described in detail later, the present inventors thought that the corrosion resistance of the stainless steel after nitriding treatment is reduced due to the presence of the martensite structure. Therefore, as described in Non-Patent Document 1, even if nitriding is performed at a low temperature of 450 ° C. or lower, depending on the state of the austenitic stainless steel to be nitrided, there is a problem that the corrosion resistance after nitriding treatment is lowered.

本発明は、上記問題点に鑑み、オーステナイト組織を有するステンレス鋼からなる母材を加工後、窒化処理を施しても母材と同程度の耐食性を示す基材をもつ被覆部材およびその製造方法を提供することを目的とする。   In view of the above problems, the present invention provides a covering member having a base material that exhibits the same degree of corrosion resistance as a base material even after being subjected to nitriding after processing a base material made of stainless steel having an austenitic structure, and a method for manufacturing the covering member. The purpose is to provide.

本発明の被覆部材は、オーステナイト組織を有するステンレス鋼からなる母材を加工した加工材の表層部を窒化してなり、40℃に保持した5mass%塩化ナトリウム水溶液中で塩化銀からなる参照電極を用いて測定した自然浸漬電位測定で−200mVより貴の自然浸漬電位を示す基材と、該表層部の表面の少なくとも一部に被覆された被膜と、を備え、前記被膜は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上であることを特徴とする。 The covering member of the present invention is formed by nitriding a surface layer portion of a processed material obtained by processing a base material made of stainless steel having an austenitic structure, and a reference electrode made of silver chloride in a 5 mass% sodium chloride aqueous solution kept at 40 ° C. a substrate showing the natural immersion potential of nobler than -200mV the natural immersion potential measurement measured using, e Bei and a coating formed on at least a portion of the surface of said surface layer portion, wherein the coating is amorphous It is characterized by being one or more of a carbon film, a chromium nitride film, a titanium nitride film, and a metal film .

本発明の被覆部材の製造方法は、オーステナイト組織を有するステンレス鋼からなる母材を加工することで加工誘起マルテンサイトが生成した加工材から加工誘起マルテンサイトを減少させる前処理工程と、該加工材に窒化処理を行い窒化層を形成する窒化処理工程と、該窒化層の表面に被膜を形成する被膜形成工程と、よりなり、前記被膜形成工程は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上を形成する工程であることを特徴とする。 The method for producing a coated member of the present invention includes a pretreatment step for reducing work-induced martensite from a work material generated by work-induced martensite by processing a base material made of stainless steel having an austenite structure, and the work material. and the nitriding treatment step of forming a nitride layer performs a nitriding treatment, and a coating formation step of forming a film on the surface of the nitride layer, Ri more name the film formation step, an amorphous carbon film, a chromium nitride film, It is a step of forming one or more of a titanium nitride film and a metal coating .

本発明の被覆部材の製造方法において、前記前処理工程は、加工誘起マルテンサイトが表面側で濃化して生成した前記加工材の表面部を除去する工程であるのが望ましい。もしくは、前記前処理工程は、前記加工材を固溶化熱処理することで加工誘起マルテンサイトをオーステナイト化する工程であるのが望ましい。   In the manufacturing method of the covering member of the present invention, it is desirable that the pretreatment step is a step of removing a surface portion of the processed material generated by concentration of processing-induced martensite on the surface side. Alternatively, the pretreatment step is preferably a step of austenitizing the work-induced martensite by performing a solution heat treatment on the processed material.

また、本発明の被覆部材の製造方法は、オーステナイト組織を有するステンレス鋼からなる母材をステンレス鋼のMd30よりも30℃以上高い温度で温間加工または熱間加工して加工材とする加工工程と、該加工材に窒化処理を行い窒化層を形成する窒化処理工程と、該窒化層の表面に被膜を形成する被膜形成工程と、よりなり、前記被膜形成工程は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上を形成する工程であることを特徴とする。 Moreover, the manufacturing method of the coating | coated member of this invention is a processing process which makes the base material which consists of stainless steel which has an austenitic structure warm-working or hot-working at 30 degreeC or more higher temperature than stainless steel Md30, and making it into a processed material When the nitriding treatment step of forming a nitride layer performs a nitriding treatment on the workpiece, and the film formation step of forming a film on the surface of the nitride layer, Ri more name the film forming step, the amorphous carbon film And a step of forming one or more of a chromium nitride film, a titanium nitride film, and a metal film .

本発明の被覆部材は、上記の条件で測定した自然浸漬電位が−200mVより貴の電位を示す基材の表面に被膜が被覆された高耐食性の被覆部材である。すなわち、基材は、母材を加工してから窒化しても、耐食性が高く保たれる。本発明の被覆部材は、基材の耐食性が高いため、基材の腐食に伴う被膜の剥離も低減され、その結果、高い耐食性が維持される。 The covering member of the present invention is a highly corrosion-resistant covering member in which a coating is coated on the surface of a base material having a natural immersion potential measured no less than −200 mV measured under the above conditions. That is, even when the base material is nitrided after the base material is processed, the corrosion resistance is kept high. Since the covering member of the present invention has high corrosion resistance of the base material, peeling of the coating film accompanying corrosion of the base material is also reduced, and as a result, high corrosion resistance is maintained.

なお、基材の耐食性は、後に詳説するように、主として、上記の加工材の表層部(すなわち窒化される部位)に存在するマルテンサイトの量に影響される。本発明の被覆部材では、加工材の表層部に存在するマルテンサイトの量を示す指標として、基材の自然浸漬電位を用いる。   The corrosion resistance of the base material is mainly influenced by the amount of martensite present in the surface layer portion (that is, the portion to be nitrided) of the processed material, as will be described in detail later. In the covering member of the present invention, the natural immersion potential of the substrate is used as an index indicating the amount of martensite present in the surface layer portion of the processed material.

また、本発明の被覆部材の製造方法によれば、窒化処理工程の前に、加工誘起マルテンサイトが生成した加工材から加工誘起マルテンサイトを減少させる(前処理工程)、もしくは、オーステナイト組織を有するステンレス鋼からなる母材をステンレス鋼のMd30よりも30℃以上高い温度で温間加工または熱間加工する(加工工程)。前処理工程または加工工程により、窒化層が形成される部位に存在する加工誘起マルテンサイトを低減することで、窒化処理後の基材の耐食性の低下が抑制される。   Moreover, according to the manufacturing method of the covering member of the present invention, before the nitriding treatment step, the processing-induced martensite is reduced from the processed material generated by the processing-induced martensite (pretreatment step) or has an austenite structure. A base material made of stainless steel is warm-worked or hot-worked at a temperature 30 ° C. higher than the stainless steel Md30 (machining process). By reducing the processing-induced martensite existing at the site where the nitrided layer is formed by the pretreatment process or the processing process, a decrease in the corrosion resistance of the base material after the nitriding process is suppressed.

以下、本発明の被覆部材およびその製造方法について詳細に説明する。   Hereinafter, the covering member of the present invention and the manufacturing method thereof will be described in detail.

図1は、オーステナイト系ステンレス鋼からなる母材を加工した加工材を窒化して得られる従来の基材を模式的に示す断面図である。オーステナイト系ステンレス鋼からなる母材を加工することで、剪断変形を助けるような応力が母材に作用すると、オーステナイト組織からなる母材の一部がマルテンサイト組織へと変態する「応力誘起変態」(「歪誘起変態」「加工誘起変態」ともいう)が起こることが知られている。加工材に窒化処理を施すと加工材の表層部が窒化され、窒化層10が形成されるが、加工材の表層部には応力誘起変態により誘起したマルテンサイト(加工誘起マルテンサイト)が存在する。マルテンサイト組織では、窒素原子が浸入しやすく窒化の進行が速いため、表層部に拡散した窒素はステンレス鋼の合金元素であるクロムと結合し、クロム、窒素、炭素の複合化合物15を形成しやすい。そのため、複合化合物15の周囲は、クロムが減少した低クロム層16となる。低クロム層16では、母材のステンレス鋼よりもクロム濃度が低下し、クロム濃度が12mass%に満たない部分は、もはやステンレス鋼ではないため、安定な不動態被膜は形成されず腐食が進行する起点となる。その結果、基材1の耐食性は、母材や加工材の耐食性よりも低下する。   FIG. 1 is a cross-sectional view schematically showing a conventional base material obtained by nitriding a processed material obtained by processing a base material made of austenitic stainless steel. By processing a base material made of austenitic stainless steel, when stress that helps shear deformation acts on the base material, a part of the base material made of austenitic structure transforms into a martensite structure. (It is also known as “strain-induced transformation” or “machining-induced transformation”). When the workpiece is subjected to nitriding treatment, the surface layer portion of the workpiece is nitrided and the nitride layer 10 is formed, but the surface layer portion of the workpiece has martensite (work-induced martensite) induced by stress-induced transformation. . In the martensite structure, nitrogen atoms easily enter and the nitriding progresses quickly. Therefore, the nitrogen diffused in the surface layer portion is easily combined with chromium, which is an alloy element of stainless steel, and easily forms a composite compound 15 of chromium, nitrogen, and carbon. . Therefore, the periphery of the composite compound 15 becomes a low chromium layer 16 in which chromium is reduced. In the low chromium layer 16, the chromium concentration is lower than that of the stainless steel of the base material, and the portion where the chromium concentration is less than 12 mass% is no longer stainless steel, so that a stable passive film is not formed and corrosion proceeds. The starting point. As a result, the corrosion resistance of the base material 1 is lower than the corrosion resistance of the base material and the processed material.

一方、本発明の被覆部材は、オーステナイト組織を有するステンレス鋼からなる母材を加工した加工材の表層部を窒化してなる基材を備えるが、基材は、40℃に保持した5mass%塩化ナトリウム水溶液中で塩化銀からなる参照電極を用いて測定した自然浸漬電位測定で−200mVより貴の自然浸漬電位を示す。すなわち、本発明の被覆部材を構成する基材は、優れた耐食性を示す。基材が−200mVより貴の自然浸漬電位を示すのは、基材の表層部に存在するクロム濃度の低い部位(低クロム層)が少ないためである。クロム濃度の低い部位は、窒化される加工材の表層部に存在するマルテンサイトの量が低減するほど形成され難くなる。加工材の表層部に存在するマルテンサイトの量が低減された基材は−200mVより貴の自然浸漬電位を示し、好ましくは−150mVよりも貴、さらに好ましくは−100mVよりも貴の自然浸漬電位を示す。なお、基材の作製方法および自然浸漬電位の測定方法は、後述する。   On the other hand, the covering member of the present invention includes a base material formed by nitriding a surface layer portion of a processed material obtained by processing a base material made of stainless steel having an austenitic structure, and the base material is 5 mass% chloride held at 40 ° C. A natural immersion potential measured from a reference electrode made of silver chloride in an aqueous sodium solution and a noble natural immersion potential from -200 mV is shown. That is, the base material constituting the covering member of the present invention exhibits excellent corrosion resistance. The reason why the base material exhibits a noble natural immersion potential of −200 mV is because there are few sites with low chromium concentration (low chromium layer) present in the surface layer portion of the base material. A portion with a low chromium concentration is less likely to be formed as the amount of martensite present in the surface layer portion of the workpiece to be nitrided is reduced. A substrate with a reduced amount of martensite present in the surface layer of the processed material exhibits a natural immersion potential nobler than -200 mV, preferably nobler than -150 mV, more preferably noble natural dip potential more than -100 mV. Indicates. In addition, the preparation method of a base material and the measuring method of natural immersion potential are mentioned later.

母材は、オーステナイト組織を有するステンレス鋼からなる。母材を構成するステンレス鋼としては、冷間加工により加工誘起マルテンサイトを生成するステンレス鋼であってもよいが、加工誘起マルテンサイトの生成量をできるだけ抑制したいため、オーステナイト組織の相安定性が高いステンレス鋼であるのが好ましい。オーステナイト組織の相安定性は、たとえば、Ms点やMd30で表される。なお、Ms点は、マルテンサイト変態の開始する温度、Md30は、加工誘起マルテンサイトの生成され易さを推定する指標であって引張真歪0.3に対して50%の加工誘起マルテンサイトが生じる温度、である。Ms点およびMd30は、ステンレス鋼の組成から以下の数式を用いてそれぞれ求めることができる。   The base material is made of stainless steel having an austenite structure. The stainless steel that forms the base material may be stainless steel that generates work-induced martensite by cold working, but because it wants to suppress the amount of work-induced martensite generated as much as possible, the phase stability of the austenite structure is low. High stainless steel is preferred. The phase stability of the austenite structure is expressed by, for example, Ms point or Md30. The Ms point is the temperature at which martensitic transformation starts, Md30 is an index for estimating the ease with which work-induced martensite is generated, and 50% of work-induced martensite is 0.3% of the true tensile strain 0.3. The resulting temperature. The Ms point and Md30 can be obtained from the composition of stainless steel using the following mathematical formulas.

Figure 0005083857
Figure 0005083857

Figure 0005083857
Figure 0005083857

なお、上記の数式において、たとえば「%C」と表されるのはステンレス鋼を100mass%としたときのステンレス鋼に含まれる炭素の割合(単位:mass%)であって、他の元素も同様である。ここで、組成の異なるA、BおよびCの3種類のオーステナイト系ステンレス鋼板(厚さ0.15mm)を固溶化熱処理した後、室温で20%板厚減少の圧延を施した加工材の加工誘起マルテンサイトの量を測定すると、表1の結果が得られる。   In the above formula, for example, “% C” is the ratio of carbon contained in the stainless steel when the stainless steel is 100 mass% (unit: mass%), and other elements are the same. It is. Here, three types of austenitic stainless steel plates (thickness 0.15 mm) A, B, and C having different compositions were subjected to solution heat treatment, and then processing induction of a workpiece subjected to rolling with a reduction in sheet thickness of 20% at room temperature. When the amount of martensite is measured, the results shown in Table 1 are obtained.

加工誘起マルテンサイトの量の測定には、SUS304の100%加工誘起マルテンサイトの飽和磁化を150emu/gとし、印加磁場18.8kOe(15MA/m)での被測定物(加工材)の磁化の値との比から推定する方法を用いることができる。被測定物の飽和磁化σs[emu/g]は、振動試料型磁力計(本測定では東英工業株式会社製VSM−3S−15)を用い、印加磁場を最大18.8kOe(15MA/m)で掃印して測定できる。マルテンサイト量は、以下の式より算出される。
マルテンサイト量[%]=(σs/150)×100
たとえば、被測定物のσsが30emu/gであれば、マルテンサイト量は20%となる。
For the measurement of the amount of processing-induced martensite, the saturation magnetization of 100% processing-induced martensite of SUS304 is 150 emu / g, and the magnetization of the object to be measured (working material) with an applied magnetic field of 18.8 kOe (15 MA / m) is used. A method of estimating from a ratio with a value can be used. The saturation magnetization σs [emu / g] of the object to be measured is a vibration sample type magnetometer (VSM-3S-15 manufactured by Toei Kogyo Co., Ltd. in this measurement), and the applied magnetic field is 18.8 kOe (15 MA / m) at maximum. You can sweep and measure. The amount of martensite is calculated from the following equation.
Martensite amount [%] = (σs / 150) × 100
For example, if σs of the object to be measured is 30 emu / g, the martensite amount is 20%.

Figure 0005083857
Figure 0005083857

なお、表1には、上記の数式を用いて算出したMs点およびMd30の値を合わせて示す。Ms点とMd30は、その値が小さい程、加工誘起マルテンサイトの生成量が抑制される。すなわち、母材は、Ms点であれば0℃以下さらには−100℃以下、Md30であれば90℃以下さらには50℃以下であるオーステナイト系ステンレス鋼であるのが好ましい。具体的には、JISに規格化されている18%Cr−8%Niを基本組成とするオーステナイト系ステンレス鋼であるのが好ましく、SUS301、SUS304、SUS316等が挙げられる。   Table 1 also shows the Ms point and Md30 values calculated using the above formula. As the values of Ms point and Md30 are smaller, the amount of processing-induced martensite generated is suppressed. That is, the base material is preferably austenitic stainless steel having an Ms point of 0 ° C. or lower, further −100 ° C. or lower, and an Md30 of 90 ° C. or lower, further 50 ° C. or lower. Specifically, austenitic stainless steel having a basic composition of 18% Cr-8% Ni standardized by JIS is preferable, and examples thereof include SUS301, SUS304, and SUS316.

また、Crは、基材の耐食性に関わる合金元素である。基材を構成するステンレス鋼のCr量は、加工材に生成されるマルテンサイト組織の量にもよるが、ステンレス鋼を100mass%としたときに12mass%以上、さらには15mass%以上、17mass%以上であるのが好ましい。Cr量が上記の範囲であれば、−200mVより貴の自然浸漬電位を示す耐食性に優れた基材が得られる。   Cr is an alloy element related to the corrosion resistance of the substrate. The amount of Cr in the stainless steel constituting the base material depends on the amount of martensite structure produced in the processed material, but when the stainless steel is 100 mass%, it is 12 mass% or more, and further 15 mass% or more, 17 mass% or more. Is preferred. When the amount of Cr is in the above range, a substrate excellent in corrosion resistance showing a noble natural immersion potential from -200 mV can be obtained.

本発明の被覆部材は、上記基材と、基材の表層部の表面の少なくとも一部に被覆された被膜と、を備える。被膜は、基材の表層部すなわち窒化により形成された窒化層の表面の少なくとも一部に被覆される。被膜は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上であるのが好ましい。被膜は、無機被膜やCrやNi等の金属被膜などであればよいが、少なくとも耐食性を有する被膜であるのが好ましい。特に好ましくは、非晶質炭素膜(DLC膜)、窒化クロム膜、窒化チタン膜などが挙げられる。これらの被膜であれば、基材の耐食性が高く維持される。特にDLC膜は、耐摩耗性、固体潤滑性などの機械的特性に優れ、耐食性のほか、絶縁性、可視光/赤外光透過率、酸素バリア性などを合わせもつため、DLC膜を被覆した本発明の被覆部材には、耐食性に加えて他の特性も付与される。 Covering member of the present invention is provided with the substrate, a coating formed on at least a portion of the surface of the surface layer portion of the substrate, the. The coating is applied to at least a part of the surface of the substrate, that is, the surface of the nitride layer formed by nitriding. The coating is preferably one or more of an amorphous carbon film, a chromium nitride film, a titanium nitride film, and a metal coating. The film may be an inorganic film or a metal film such as Cr or Ni, but is preferably a film having at least corrosion resistance. Particularly preferred are an amorphous carbon film (DLC film), a chromium nitride film, a titanium nitride film, and the like. With these coatings, the corrosion resistance of the substrate is maintained high. In particular, the DLC film is excellent in mechanical properties such as wear resistance and solid lubricity, and in addition to corrosion resistance, it also has insulation, visible / infrared light transmittance, oxygen barrier properties, etc., so the DLC film is coated. In addition to corrosion resistance, other characteristics are also imparted to the covering member of the present invention.

被膜の膜厚に特に限定はないが、たとえばDLC膜であれば、0.05〜50μmであるのが好ましい。DLC膜の膜厚がこの範囲にあれば、優れた耐食性を発揮するとともに、基材との密着性にも優れる。 Although there is no particular limitation on the film thickness of the coating , for example, in the case of a DLC film, it is preferably 0.05 to 50 μm. If the film thickness of the DLC film is within this range, it exhibits excellent corrosion resistance and excellent adhesion to the substrate.

本発明の被覆部材の製造方法は、前処理工程または加工工程と、窒化処理工程と、被膜形成工程と、よりなる。本発明の被覆部材の製造方法は、表層部を窒化する前の加工材を、加工誘起マルテンサイトが無いあるいは少ない状態とすることで、窒化処理による耐食性の低下を抑制するものである。そのため、オーステナイト組織を有するステンレス鋼からなる母材を加工することで加工誘起マルテンサイトが生成した加工材から加工誘起マルテンサイトを減少させる前処理工程、あるいは、オーステナイト組織を有するステンレス鋼からなる母材をステンレス鋼のMd30よりも30℃以上高い温度で温間加工または熱間加工して加工材とする加工工程、を行う。   The manufacturing method of the covering member of the present invention includes a pretreatment process or a processing process, a nitriding process, and a film forming process. The manufacturing method of the covering member of the present invention suppresses a decrease in corrosion resistance due to nitriding treatment by setting the processed material before nitriding the surface layer to a state in which there is little or no processing-induced martensite. Therefore, a pretreatment step for reducing the processing-induced martensite from the processing material generated by processing-induced martensite by processing a base material made of stainless steel having an austenitic structure, or a base material consisting of stainless steel having an austenitic structure Is processed at a temperature higher by 30 ° C. or higher than Md30 of stainless steel to obtain a processed material by hot working or hot working.

前処理工程は、母材を加工することで加工誘起マルテンサイトが生成した加工材から加工誘起マルテンサイトを減少させる工程である。母材は、転造加工、プレス加工などの塑性加工、切削加工、研削加工、剪断加工などの一般的な加工法で加工されればよいが、加工誘起マルテンサイトの生成量は、加工条件によっても変化する。そのため、加工誘起マルテンサイトが生成されにくい条件で加工を行うのが望ましい。得られる加工材には、加工誘起マルテンサイトが生成するが、加工材の表面側で濃化して存在するのが一般的である。   The pretreatment step is a step of reducing the processing induced martensite from the processed material generated by the processing induced martensite by processing the base material. The base material may be processed by general processing methods such as plastic processing such as rolling and press processing, cutting processing, grinding processing, and shear processing, but the amount of processing-induced martensite generated depends on processing conditions. Also changes. For this reason, it is desirable to perform processing under conditions in which processing-induced martensite is difficult to be generated. In the obtained processed material, processing-induced martensite is generated, but is generally concentrated on the surface side of the processed material.

加工材から加工誘起マルテンサイトを減少させる方法としては、加工材の表面部を除去する方法がある。たとえば、切削加工のような表面加工の場合には、加工誘起マルテンサイトは加工材の表面側で濃化して生成するため、加工材の表面部を除去することで、後の窒化処理工程で窒化される表層部の加工誘起マルテンサイトを減少させることができる。加工材の表面部を除去する際には、加工材の表面から数μmまでを除去すればよいため、基材に大きな寸法変化が生じることがない。また、表面部のみを除去すればよく、加工材全体を処理する必要がないため加工材の変形も抑制される。   As a method of reducing the processing-induced martensite from the processed material, there is a method of removing the surface portion of the processed material. For example, in the case of surface processing such as cutting, work-induced martensite is concentrated and generated on the surface side of the work material. Therefore, the surface portion of the work material is removed, so that nitriding is performed in a subsequent nitriding process. It is possible to reduce the processing-induced martensite in the surface layer portion. When removing the surface portion of the processed material, it is only necessary to remove several μm from the surface of the processed material, so that a large dimensional change does not occur in the base material. Further, only the surface portion needs to be removed, and since it is not necessary to process the entire processed material, deformation of the processed material is also suppressed.

加工材の表面部を除去するには、酸を用いて表面部を溶解するとよい。具体的には、電解溶解または化学溶解により表面部を溶解して除去する方法が挙げられる。特に、電解研磨または化学研磨であれば、研磨により加工材に応力が作用することがなく、加工誘起マルテンサイトが生成されることがないため望ましい。また、表面粗さも小さく抑えられる(十点平均粗さRzjisで0.1〜3μm)。電解研磨や化学研磨は、ステンレス鋼の表面処理として通常行われている条件で行えばよい。   In order to remove the surface portion of the workpiece, the surface portion may be dissolved using an acid. Specifically, a method of dissolving and removing the surface portion by electrolytic dissolution or chemical dissolution can be mentioned. In particular, electrolytic polishing or chemical polishing is desirable because stress does not act on the workpiece due to polishing and processing-induced martensite is not generated. Further, the surface roughness can be kept small (10-point average roughness Rzjis is 0.1 to 3 μm). Electropolishing and chemical polishing may be performed under the conditions normally used for surface treatment of stainless steel.

前処理工程で除去される表面部は、0.1〜20μmさらには1〜20μmの厚みで除去されるのが望ましい。また、加工材から加工誘起マルテンサイトを減少させる方法として、加工材を固溶化熱処理することで加工誘起マルテンサイトをオーステナイト化する方法を用いてもよい。固溶化熱処理は、たとえば、950〜1150℃で1分以上保持した後、低温に急冷するとよい。   It is desirable that the surface portion removed in the pretreatment step is removed with a thickness of 0.1 to 20 μm, or further 1 to 20 μm. Further, as a method of reducing the work-induced martensite from the work material, a method of converting the work-induced martensite to austenite by subjecting the work material to a solution heat treatment may be used. In the solution heat treatment, for example, after being held at 950 to 1150 ° C. for 1 minute or longer, it may be rapidly cooled to a low temperature.

本発明の被覆部材の製造方法では、上記の前処理工程を、母材をステンレス鋼のMd30よりも30℃以上高い温度で温間加工または熱間加工して加工材とする加工工程とすることもできる。加工工程では、加工誘起マルテンサイトが生成され難い温度条件で母材が加工される。温間加工または熱間加工の温度は、加工される母材の合金組成にもよるが、Md30よりも30℃以上さらには60℃以上高い温度で加工するのが望ましい。加工方法に特に限定はなく、転造加工、プレス加工などの塑性加工、切削加工、研削加工、剪断加工などが挙げられる。   In the manufacturing method of the covering member of the present invention, the pretreatment step is a processing step in which the base material is warm-worked or hot-worked at a temperature higher by 30 ° C. than Md30 of stainless steel to obtain a work material. You can also. In the processing step, the base material is processed under a temperature condition in which processing-induced martensite is difficult to be generated. Although the temperature of warm working or hot working depends on the alloy composition of the base material to be worked, it is desirable to work at a temperature higher by 30 ° C. or more by 60 ° C. than Md30. The processing method is not particularly limited, and examples thereof include plastic processing such as rolling processing and press processing, cutting processing, grinding processing, and shearing processing.

なお、前処理工程および加工工程において用いられる母材に関しては、既に述べた通りである。   The base material used in the pretreatment process and the processing process is as described above.

窒化処理工程は、加工材に窒化処理を行い窒化層を形成する工程である。前処理工程または加工工程を経た加工材では、窒化される表層部のほとんどをオーステナイト組織が占める。オーステナイト組織には窒化により窒素原子が固溶するが、上記の複合化合物は形成されにくい。そのため、前処理工程または加工工程を経た加工材を窒化処理して得られる基材は、Cr濃度の低い部分が形成されにくく、高い耐食性を示す。具体的には、基材は、40℃に保持した5mass%塩化ナトリウム水溶液中で塩化銀からなる参照電極を用いて測定した自然浸漬電位測定で−200mVより貴の自然浸漬電位、さらには、−150mV、−100mVよりも貴の自然浸漬電位を示すのが望ましい。   The nitriding step is a step of forming a nitrided layer by nitriding the workpiece. In the processed material that has undergone the pretreatment step or the processing step, the austenite structure occupies most of the surface layer portion to be nitrided. Nitrogen atoms are dissolved in the austenite structure by nitriding, but the above complex compound is hardly formed. Therefore, the base material obtained by nitriding the processed material that has undergone the pretreatment process or the processing process is difficult to form a portion with a low Cr concentration and exhibits high corrosion resistance. Specifically, the base material has a natural soaking potential nobler than -200 mV as measured by a natural soaking potential measured using a reference electrode made of silver chloride in a 5 mass% sodium chloride aqueous solution kept at 40 ° C., It is desirable to show a noble natural immersion potential more than 150 mV and -100 mV.

窒化処理工程は、イオン窒化法、ガス窒化法または溶融塩窒化法により窒化処理する工程であるのが望ましく、ステンレス鋼の表面処理として通常行われている条件で行えば、いずれの方法を用いても所望の基材を作製することができる。たとえば、ガス窒化法であれば、アンモニアガスとともに不動態被膜を破壊する腐食性ガスを導入することで、低い処理温度でも加工材の表面に窒素が固溶する。また、溶融塩窒化法では、窒化物イオン(N3−)を含有する溶融塩を用いるが、この際、溶融塩を電解質として電気化学的に窒化処理を行うことで、ステンレス鋼の表面に不動態被膜があっても、非処理材の表層部に容易に窒化層を形成することができる。 The nitriding treatment step is preferably a nitriding treatment by an ion nitriding method, a gas nitriding method or a molten salt nitriding method, and any method can be used as long as it is performed under the conditions normally used for the surface treatment of stainless steel. Can also produce a desired substrate. For example, in the case of a gas nitriding method, nitrogen is dissolved on the surface of the workpiece even at a low processing temperature by introducing a corrosive gas that destroys the passive film together with ammonia gas. In the molten salt nitriding method, a molten salt containing nitride ions (N 3− ) is used. At this time, an electrochemical nitriding treatment is performed on the surface of the stainless steel by using the molten salt as an electrolyte. Even if there is a dynamic film, a nitride layer can be easily formed on the surface layer of the non-treated material.

なお、窒化処理の処理温度に特に限定はないが、350〜600℃さらには370〜470℃で行われるのが望ましい。また、窒化深さにも特に限定はないが、0.1〜200μmさらには1〜50μmであるのが望ましい。窒化処理温度や窒化深さが上記の範囲であれば、基材の表面を十分な硬度にできるとともに、基材と被膜との密着性の点で望ましい。 The nitriding treatment temperature is not particularly limited, but is preferably 350 to 600 ° C., more preferably 370 to 470 ° C. The nitriding depth is not particularly limited, but is preferably 0.1 to 200 μm, more preferably 1 to 50 μm. When the nitriding temperature and the nitriding depth are in the above ranges, the surface of the substrate can be made sufficiently hard, and it is desirable in terms of adhesion between the substrate and the coating .

被膜形成工程は、窒化層の表面に被膜を形成する工程である。被膜は、プラズマCVD法、イオンプレーティング法、スパッタリング法など、既に公知のCVD法、PVD法により形成することができる。しかし、スパッタリング法に代表されるように、PVD法は指向性の成膜方法である。よって、PVD法で均一に成膜するためには、装置内に複数のターゲットを配置したり成膜する基材を回転させたりすることが必要となる。その結果、成膜装置の構造が複雑化し、高価になる。また、PVD法では、複雑な形状の基材、たとえば、円筒形状の基材の内周面への成膜は容易ではない。 The film forming step is a step of forming a film on the surface of the nitride layer. The coating can be formed by a known CVD method or PVD method such as a plasma CVD method, an ion plating method, or a sputtering method. However, as represented by the sputtering method, the PVD method is a directional film forming method. Therefore, in order to form a film uniformly by the PVD method, it is necessary to dispose a plurality of targets in the apparatus or to rotate a substrate on which the film is formed. As a result, the structure of the film forming apparatus becomes complicated and expensive. In addition, in the PVD method, it is not easy to form a film on an inner peripheral surface of a base material having a complicated shape, for example, a cylindrical base material.

一方、プラズマCVD法は、反応ガスにより成膜するため、複雑な形状のものにでも容易に成膜することができる。また、成膜装置の構造も単純で安価である。プラズマCVD法には、たとえば、高周波放電を利用する高周波プラズマCVD法や、直流放電を利用する直流プラズマCVD法等がある。特に、直流プラズマCVD法は、真空炉と直流電源とからなるシンプルな構成の成膜装置で実施できるため好適である。また、窒化処理工程がプラズマ窒化処理法により窒化処理する工程であれば、真空炉内に導入するガスの種類を変更するのみで、同じ装置を用いて窒化処理工程と被膜形成工程とを行うことができる。   On the other hand, since the plasma CVD method forms a film with a reactive gas, it can be easily formed even in a complicated shape. Further, the structure of the film forming apparatus is simple and inexpensive. Examples of the plasma CVD method include a high-frequency plasma CVD method using high-frequency discharge and a direct-current plasma CVD method using direct-current discharge. In particular, the direct-current plasma CVD method is preferable because it can be performed by a film forming apparatus having a simple configuration including a vacuum furnace and a direct-current power source. In addition, if the nitriding process is a nitriding process using a plasma nitriding process, the nitriding process and the film forming process are performed using the same apparatus only by changing the type of gas introduced into the vacuum furnace. Can do.

たとえば、非晶質炭素膜を、直流プラズマCVD法により成膜する場合には、まず、真空容器内に基材を配置して、反応ガスおよびキャリアガスを導入する。そして、放電により反応ガス中のプラズマイオンを基材に付着させればよい。反応ガスには、メタン(CH)、アセチレン(C)等の炭化水素ガス、珪素を含む非晶質炭素膜(DLC−Si膜)を成膜するのであれば、TMS[Si(CH]、SiH、SiCl、SiH等の珪素化合物ガスを用い、キャリアガスには水素ガス、アルゴンガス等を用いればよい。 For example, when an amorphous carbon film is formed by a direct-current plasma CVD method, first, a base material is placed in a vacuum vessel, and a reaction gas and a carrier gas are introduced. Then, plasma ions in the reaction gas may be attached to the substrate by discharge. If an amorphous carbon film (DLC-Si film) containing hydrocarbon gas such as methane (CH 4 ) or acetylene (C 2 H 2 ) or silicon is formed as the reaction gas, TMS [Si ( A silicon compound gas such as CH 3 ) 4 ], SiH 4 , SiCl 4 , or SiH 2 F 4 may be used, and hydrogen gas, argon gas, or the like may be used as the carrier gas.

なお、被膜の成膜温度に特に限定はないが、600℃以下が望ましい。また、被膜の成膜時間は、所望の膜厚に応じて適宜選択すればよい。 The film forming temperature is not particularly limited, but is preferably 600 ° C. or lower. The film formation time may be appropriately selected according to the desired film thickness.

以上、本発明の被覆部材およびその製造方法の実施形態を説明したが、本発明の被覆部材およびその製造方法は、上記実施形態に限定されるものではない。本発明の被覆部材およびその製造方法は、本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。   As mentioned above, although embodiment of the coating | coated member of this invention and its manufacturing method was described, the coating | coated member of this invention and its manufacturing method are not limited to the said embodiment. The covering member and the manufacturing method thereof according to the present invention can be implemented in various forms with modifications, improvements, etc. that can be made by those skilled in the art without departing from the gist of the present invention.

次に、実施例を挙げて本発明をより具体的に説明する。   Next, the present invention will be described more specifically with reference to examples.

[基材の作製]
母材として、オーステナイト系ステンレス鋼SUS304製の丸棒状母材(直径6.5mm、長さ60mm、表面粗さRzjis1.5μm)を準備した。上記の数式から算出したSUS304のMs点は−150℃、Md30は30℃であった。丸棒状母材の表面には、母材に生じる剪断変形を極力抑えた条件で切削加工を施し(加工工程)、#A0の基材を作製した。
[Production of substrate]
As a base material, a round bar base material (diameter 6.5 mm, length 60 mm, surface roughness Rzjis 1.5 μm) made of austenitic stainless steel SUS304 was prepared. The Ms point of SUS304 calculated from the above formula was −150 ° C., and Md30 was 30 ° C. On the surface of the round bar-shaped base material, cutting was performed under the condition that the shear deformation generated in the base material was suppressed as much as possible (processing step), and a # A0 base material was produced.

また、#A0と同様な加工を施した後、後述のプラズマ窒化処理法により窒化処理を施し(窒化処理工程)、#A0−1および#A0−2の基材を作製した。なお、#A0−1は500℃、#A0−2は400℃、で窒化を行った。   Further, after performing the same processing as # A0, nitriding treatment was performed by a plasma nitriding treatment method described later (nitriding treatment step), and # A0-1 and # A0-2 substrates were produced. Note that nitriding was performed at 500 ° C. for # A0-1 and 400 ° C. for # A0-2.

また、#A0と同様な加工を施した後、市販の化学研磨処理液を所定の条件にて用い、最表面から5μmまでの表面部を除去した(前処理工程)。その後、後述のプラズマ窒化処理法により窒化処理を施し(窒化処理工程)、#A1−2の基材を得た。なお、#A1−2は400℃で窒化を行った。   Further, after the same processing as # A0, a commercially available chemical polishing solution was used under predetermined conditions, and the surface portion from the outermost surface to 5 μm was removed (pretreatment step). Thereafter, nitriding treatment was performed by a plasma nitriding treatment method described later (nitriding treatment step) to obtain a base material of # A1-2. In addition, # A1-2 was nitrided at 400 ° C.

[実施例1]
#A1−2の基材の表面に後述のプラズマCVD法によりDLC−Si膜を成膜し(被膜形成工程)、実施例1の被覆部材を作製した。
[Example 1]
A DLC-Si film was formed on the surface of the base material of # A1-2 by the plasma CVD method described later (film formation process), and the covering member of Example 1 was produced.

[比較例1]
#A0−1の基材の表面に後述のプラズマCVD法によりDLC−Si膜を成膜し、比較例1の被覆部材を作製した。
[Comparative Example 1]
A DLC-Si film was formed on the surface of the base material of # A0-1 by the plasma CVD method described later, and a covering member of Comparative Example 1 was produced.

[比較例2]
#A0−2の基材の表面に後述のプラズマCVD法によりDLC−Si膜を成膜し、比較例2の被覆部材を作製した。
[Comparative Example 2]
A DLC-Si film was formed on the surface of the base material of # A0-2 by the plasma CVD method described later, and a covering member of Comparative Example 2 was produced.

<窒化処理工程および被膜形成工程>
窒化処理およびDLC−Si膜の成膜は、図2に示す直流プラズマCVD装置を用いて行った。図2に示すように、直流プラズマCVD装置2は、ステンレス製の容器20と、基台21と、ガス導入管22と、ガス導出管23とを備える。ガス導入管22は、バルブ(図略)を介して各種ガスボンベ(図略)に接続される。ガス導出管23は、バルブ(図略)を介してロータリーポンプ(図略)および拡散ポンプ(図略)に接続される。
<Nitriding process and film formation process>
The nitriding treatment and the formation of the DLC-Si film were performed using a DC plasma CVD apparatus shown in FIG. As shown in FIG. 2, the direct-current plasma CVD apparatus 2 includes a stainless steel container 20, a base 21, a gas introduction pipe 22, and a gas outlet pipe 23. The gas introduction pipe 22 is connected to various gas cylinders (not shown) through valves (not shown). The gas outlet pipe 23 is connected to a rotary pump (not shown) and a diffusion pump (not shown) via a valve (not shown).

<プラズマ窒化処理>
容器20内に設置された基台21の上に、加工材3を配置した。次に、容器20を密閉し、ガス導出管23に接続されたロータリーポンプおよび拡散ポンプにより、容器20内のガスを排気した。容器20内にガス導入管22から水素ガスを14sccm(standard cc/min)導入し、ガス圧を約133Paとした。その後、容器20の内側に設けたステンレス製陽極板24と基台21との間に200Vの直流電圧を印加して、放電を開始した。そして、加工材3の表面温度が窒化処理温度になるまで、イオン衝撃による昇温を行った。次に、ガス導入管22から、窒素ガス500sccmおよび水素ガス40sccmを導入し、圧力約425Pa、電圧300V(電流1〜2A)、400℃または500℃でプラズマ窒化処理を1時間行った。得られた基材の断面組織を観察したところ、窒化深さは約10μmであった。
<Plasma nitriding treatment>
The workpiece 3 was placed on the base 21 installed in the container 20. Next, the container 20 was sealed, and the gas in the container 20 was exhausted by a rotary pump and a diffusion pump connected to the gas outlet pipe 23. Hydrogen gas was introduced into the container 20 through the gas introduction pipe 22 at 14 sccm (standard cc / min), and the gas pressure was set to about 133 Pa. Thereafter, a DC voltage of 200 V was applied between the stainless steel anode plate 24 and the base 21 provided inside the container 20 to start discharging. Then, the temperature was raised by ion bombardment until the surface temperature of the workpiece 3 reached the nitriding temperature. Next, nitrogen gas 500 sccm and hydrogen gas 40 sccm were introduced from the gas introduction tube 22, and plasma nitriding was performed at a pressure of about 425 Pa, a voltage of 300 V (current 1 to 2 A), 400 ° C. or 500 ° C. for 1 hour. When the cross-sectional structure of the obtained base material was observed, the nitriding depth was about 10 μm.

プラズマ窒化処理後、ガス導入管22から水素ガスとアルゴンガスとを30sccmずつ導入し、圧力約500Pa、電圧250V(電流1〜2A)とし、プラズマ窒化処理と同じ温度でスパッタリングし、基材の表面に微細な凹凸を形成した。   After the plasma nitriding treatment, hydrogen gas and argon gas are introduced through the gas introduction tube 22 by 30 sccm at a pressure of about 500 Pa and a voltage of 250 V (current 1 to 2 A), and sputtering is performed at the same temperature as the plasma nitriding treatment. Fine irregularities were formed on the surface.

<DLC−Si膜の成膜>
プラズマ窒化処理に引き続き基材の表面にDLC−Si膜を成膜する際には、ガス導入管22から原料ガスであるメタンとTMSを供給し、各ガスを、メタン:50sccm、TMS:1sccm、水素ガス:30sccm、アルゴンガス:30sccmの流量で導入し、圧力約400Pa、電圧300V(電流1〜2A)とし、プラズマ窒化処理と同じ温度で40分間成膜して、膜厚が約3μmのDLC−Si膜を得た。
<DLC-Si film deposition>
When the DLC-Si film is formed on the surface of the base material following the plasma nitriding treatment, methane and TMS, which are raw material gases, are supplied from the gas introduction pipe 22, and each gas is supplied with methane: 50 sccm, TMS: 1 sccm, Hydrogen gas: 30 sccm, argon gas: introduced at a flow rate of 30 sccm, a pressure of about 400 Pa, a voltage of 300 V (current 1 to 2 A), a film formed for 40 minutes at the same temperature as the plasma nitriding treatment, and a DLC film thickness of about 3 μm A Si film was obtained.

[基材の評価]
以上の手順により得られた4種類の基材に対して、自然浸漬電位および腐食速度を測定した。測定方法を図3および図4を用いて説明する。
[Evaluation of substrate]
The natural immersion potential and the corrosion rate were measured for the four types of substrates obtained by the above procedure. The measurement method will be described with reference to FIGS.

自然浸漬電位測定には、上記4種類の基材のいずれかを用いて作製した試料電極E1と、塩化銀からなる参照電極E2と、電位計(図示せず)と、容器Cと、からなる測定装置を用いた(図3)。容器Cに、試験液Lとして5mass%塩化ナトリウム水溶液を満たし、試験液Lの温度を40℃とした後、試料電極E1および参照電極E2を挿入した。この状態で、試料電極E1と参照電極E2との間の電位差ΔE(自然浸漬電位)を電位計で測定した。結果を表2に示す。   The natural immersion potential measurement includes a sample electrode E1 produced using any of the above four types of base materials, a reference electrode E2 made of silver chloride, an electrometer (not shown), and a container C. A measuring device was used (FIG. 3). The container C was filled with a 5 mass% sodium chloride aqueous solution as the test liquid L, and the temperature of the test liquid L was set to 40 ° C., and then the sample electrode E1 and the reference electrode E2 were inserted. In this state, the potential difference ΔE (natural immersion potential) between the sample electrode E1 and the reference electrode E2 was measured with an electrometer. The results are shown in Table 2.

また、腐食速度は、分極抵抗法により測定した。腐食速度の測定には、上記4種類の基材のいずれかを用いて作製した試料電極E1と、塩化銀からなる参照電極E2と、白金電極(対極)E3と、電位計(図示せず)と、容器Cと、からなる測定装置を用いた(図4)。容器Cに、試験液Lとして5mass%塩化ナトリウム水溶液を満たし、試験液Lの温度を40℃とした後、電極E1、E2およびE3を挿入した。試料電極E1と白金電極E3との間に微少電流ΔI(ΔEが10mVを超えないように調整する。本測定では0.1〜10μAの任意の値。)を流して分極させたときの電位の変化量を、試料電極E1と参照電極E2との間の電位差ΔEを電位計で測定することにより求めた。腐食速度は、ΔI/ΔEに比例するため、それぞれの基材についてΔI/ΔE値を求めることで、相対的な腐食速度を得た。結果を表2に示すが、表2において腐食速度は、#A0の基材の腐食速度を1としたときの相対値とした。なお、本測定では、上記の測定装置として北斗電工株式会社製腐食速度計HK−103を用いた。   The corrosion rate was measured by the polarization resistance method. For the measurement of the corrosion rate, a sample electrode E1 produced using any of the above four types of base materials, a reference electrode E2 made of silver chloride, a platinum electrode (counter electrode) E3, and an electrometer (not shown) And a measuring device comprising the container C (FIG. 4). The container C was filled with a 5 mass% sodium chloride aqueous solution as the test liquid L, and the temperature of the test liquid L was set to 40 ° C., and then the electrodes E1, E2, and E3 were inserted. A potential of the electric potential when polarized by flowing a minute current ΔI (adjusted so that ΔE does not exceed 10 mV. In this measurement, an arbitrary value of 0.1 to 10 μA) is passed between the sample electrode E1 and the platinum electrode E3. The amount of change was determined by measuring the potential difference ΔE between the sample electrode E1 and the reference electrode E2 with an electrometer. Since the corrosion rate is proportional to ΔI / ΔE, the relative corrosion rate was obtained by obtaining the ΔI / ΔE value for each substrate. The results are shown in Table 2. In Table 2, the corrosion rate is a relative value when the corrosion rate of the # A0 substrate is 1. In this measurement, a corrosion rate meter HK-103 manufactured by Hokuto Denko Corporation was used as the above measuring device.

Figure 0005083857
Figure 0005083857

切削加工のみを施した加工材の状態である#A0の基材は、+30mVで貴な自然浸漬電位を示した。すなわち、#A0の基材は耐食性に優れる。   The base material of # A0, which is a state of a processed material that has been subjected only to cutting, showed a noble natural immersion potential at +30 mV. That is, the # A0 base material is excellent in corrosion resistance.

次に、切削加工後に窒化処理を施した#A0−1および#A0−2の基材では、自然浸漬電位はそれぞれ−400mV、−210mV、腐食速度はそれぞれ#A0の基材の70倍、10倍以上であった。つまり、#A0の基材には切削加工により生成された加工誘起マルテンサイトが存在したため、この基材に窒化処理を施すことで、耐食性が低下した。また、窒化処理温度を低温の400℃とした#A0−2の基材では、500℃で窒化処理した#A0−1の基材よりも貴の自然浸漬電位を示したが、加工誘起マルテンサイトが存在する基材に対しては低温処理をしても耐食性の低下を抑制することはできなかった。   Next, in the # A0-1 and # A0-2 base materials that were subjected to nitriding after cutting, the natural immersion potentials were -400 mV and -210 mV, respectively, and the corrosion rates were 70 times that of the # A0 base material. It was more than twice. That is, since the processing-induced martensite generated by the cutting process was present in the # A0 base material, the corrosion resistance was lowered by nitriding the base material. In addition, the # A0-2 base material having a low nitriding temperature of 400 ° C. showed a higher natural immersion potential than the # A0-1 base material nitrided at 500 ° C., but the processing-induced martensite Even if the base material containing slag was subjected to a low temperature treatment, it was not possible to suppress a decrease in corrosion resistance.

窒化処理を施す前に表面を化学研磨した#A1−2の基材の自然浸漬電位は+30mV、腐食速度は(#0の基材を1としたとき)0.6であった。すなわち、#A1−2の基材は、窒化処理後の耐食性の低下が表れなかった。これは、表面部を化学研磨したことで、切削加工で生成された加工誘起マルテンサイトが濃化して存在する部分が除去されたからである。   The natural immersion potential of the # A1-2 base material whose surface was chemically polished before the nitriding treatment was +30 mV, and the corrosion rate was 0.6 (when the base material of # 0 was 1). That is, the # A1-2 base material showed no reduction in corrosion resistance after nitriding. This is because the portion where the work-induced martensite produced by cutting is concentrated and present is removed by chemically polishing the surface portion.

[被覆部材の評価]
実施例1、比較例1および2の被覆部材に対して、塩水噴霧試験を行った。塩水噴霧試験は、40℃に保った試験槽内に被覆部材を配置し、試験槽内に試験液として5mass%塩化ナトリウム水溶液を霧状にして吹き込んで行った。試験開始から48時間後の被覆部材の表面を目視で観察し、錆の発生の有無を確認した。結果を表3に示す。なお、表3において、「○」は錆が発生しなかった、「×」は錆が発生したことを示す。
[Evaluation of coated member]
A salt spray test was performed on the covering members of Example 1 and Comparative Examples 1 and 2. The salt spray test was performed by placing a covering member in a test tank maintained at 40 ° C., and spraying a 5 mass% sodium chloride aqueous solution as a test liquid in the form of a mist into the test tank. The surface of the covering member 48 hours after the start of the test was visually observed to check for the occurrence of rust. The results are shown in Table 3. In Table 3, “◯” indicates that rust did not occur, and “x” indicates that rust occurred.

Figure 0005083857
Figure 0005083857

実施例1の被覆部材は、DLC−Si膜の剥離も見られず、耐食性に優れた。一方、比較例1および2の被覆部材では、錆が発生した。これは、DLC−Si膜の厚さ方向に貫通する欠陥から試験液が侵入し、基材の表面を腐食させたためである。   The covering member of Example 1 was excellent in corrosion resistance without peeling of the DLC-Si film. On the other hand, in the covering members of Comparative Examples 1 and 2, rust was generated. This is because the test solution entered from a defect penetrating in the thickness direction of the DLC-Si film and corroded the surface of the substrate.

加工誘起マルテンサイトをもつ加工材を窒化して得られる従来の基材を模式的に示す断面図である。It is sectional drawing which shows typically the conventional base material obtained by nitriding the processing material which has a process induction martensite. 直流プラズマCVD装置の概略図である。It is the schematic of a direct-current plasma CVD apparatus. 基材の自然浸漬電位の測定に用いる装置の概略図である。It is the schematic of the apparatus used for the measurement of the natural immersion potential of a base material. 分極抵抗法による腐食速度の測定に用いる装置の概略図である。It is the schematic of the apparatus used for the measurement of the corrosion rate by a polarization resistance method.

Claims (13)

オーステナイト組織を有するステンレス鋼からなる母材を加工した加工材の表層部を窒化してなり、40℃に保持した5mass%塩化ナトリウム水溶液中で塩化銀からなる参照電極を用いて測定した自然浸漬電位測定で−200mVより貴の自然浸漬電位を示す基材と、
該表層部の表面の少なくとも一部に被覆された被膜と、
を備え、前記被膜は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上であることを特徴とする被覆部材。
Natural immersion potential measured using a reference electrode made of silver chloride in a 5 mass% sodium chloride aqueous solution formed by nitriding the surface layer portion of a processed material obtained by processing a base material made of stainless steel having an austenitic structure. A substrate showing a natural immersion potential nobler than -200 mV by measurement,
A coating coated on at least a part of the surface of the surface layer portion;
Bei example, said coating is an amorphous carbon film, a chromium nitride film, the covering member, characterized in that at least one of titanium nitride film and a metal film.
前記ステンレス鋼のMs点が0℃以下かつMd30が90℃以下である請求項1記載の被覆部材。   The covering member according to claim 1 whose Ms point of said stainless steel is 0 ° C or less and Md30 is 90 ° C or less. 前記基材は、−150mVより貴の自然浸漬電位を示す請求項1記載の被覆部材。   The covering member according to claim 1, wherein the base material exhibits a natural immersion potential nobler than −150 mV. オーステナイト組織を有するステンレス鋼からなる母材を加工することで加工誘起マルテンサイトが生成した加工材から加工誘起マルテンサイトを減少させる前処理工程と、
該加工材に窒化処理を行い窒化層を形成する窒化処理工程と、
該窒化層の表面に被膜を形成する被膜形成工程と、
よりなり、前記被膜形成工程は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上を形成する工程であることを特徴とする被覆部材の製造方法。
A pretreatment step for reducing the processing-induced martensite from the processing material generated by the processing-induced martensite by processing a base material made of stainless steel having an austenitic structure;
Nitriding treatment step of nitriding the work material to form a nitride layer;
A film forming step of forming a film on the surface of the nitride layer;
Ri More Na, the film forming step, manufacture of the covering member, characterized in that a step of forming an amorphous carbon film, a chromium nitride film, one or more of titanium nitride film and a metal film Method.
前記前処理工程は、加工誘起マルテンサイトが表面側で濃化して生成した前記加工材の表面部を除去する工程である請求項記載の被覆部材の製造方法。 The said pre-processing process is a manufacturing method of the coating | coated member of Claim 4 which is a process of removing the surface part of the said processed material which the process induction martensite concentrated on the surface side and produced | generated. 前記前処理工程は、電解溶解または化学溶解により前記表面部を溶解して除去する工程である請求項記載の被覆部材の製造方法。 The method for manufacturing a covering member according to claim 5 , wherein the pretreatment step is a step of dissolving and removing the surface portion by electrolytic dissolution or chemical dissolution. 前記前処理工程は、前記加工材を固溶化熱処理することで加工誘起マルテンサイトをオーステナイト化する工程である請求項記載の被覆部材の製造方法。 The said pre-processing process is a manufacturing method of the coating | coated member of Claim 4 which is a process of austenitizing a process induction martensite by carrying out the solution heat treatment of the said processed material. オーステナイト組織を有するステンレス鋼からなる母材をステンレス鋼のMd30よりも30℃以上高い温度で温間加工または熱間加工して加工材とする加工工程と、
該加工材に窒化処理を行い窒化層を形成する窒化処理工程と、
該窒化層の表面に被膜を形成する被膜形成工程と、
よりなり、前記被膜形成工程は、非晶質炭素膜、窒化クロム膜、窒化チタン膜および金属被膜のうちの1種または2種以上を形成する工程であることを特徴とする被覆部材の製造方法。
A processing step in which a base material made of stainless steel having an austenite structure is warm-worked or hot-worked at a temperature 30 ° C. or higher than Md30 of stainless steel to obtain a work material;
Nitriding treatment step of nitriding the work material to form a nitride layer;
A film forming step of forming a film on the surface of the nitride layer;
Ri More Na, the film forming step, manufacture of the covering member, characterized in that a step of forming an amorphous carbon film, a chromium nitride film, one or more of titanium nitride film and a metal film Method.
窒化処理後の前記加工材は、40℃に保持した5mass%塩化ナトリウム水溶液中で塩化銀からなる参照電極を用いて測定した自然浸漬電位測定で−200mVより貴の自然浸漬電位を示す請求項4〜8のいずれかに記載の被覆部材の製造方法。 5. The processed material after nitriding treatment exhibits a natural immersion potential nobler than −200 mV as measured by a natural immersion potential measured using a reference electrode made of silver chloride in a 5 mass% sodium chloride aqueous solution maintained at 40 ° C. 5. The manufacturing method of the coating | coated member in any one of -8 . 前記自然浸漬電位は、−150mVよりも貴である請求項記載の被覆部材の製造方法。 The method for manufacturing a covering member according to claim 9 , wherein the natural immersion potential is nobler than −150 mV. 前記ステンレス鋼のMs点が0℃以下かつMd30が90℃以下である請求項4〜8のいずれかに記載の被覆部材の製造方法。 The method for producing a covering member according to any one of claims 4 to 8 , wherein the stainless steel has an Ms point of 0 ° C or lower and an Md30 of 90 ° C or lower. 前記窒化処理工程は、イオン窒化法、ガス窒化法または溶融塩窒化法により窒化処理する工程である請求項4〜8のいずれかに記載の被覆部材の製造方法。 The method for manufacturing a covering member according to any one of claims 4 to 8 , wherein the nitriding treatment step is a nitriding treatment by an ion nitriding method, a gas nitriding method, or a molten salt nitriding method. 前記窒化処理工程は、350〜600℃で窒化処理する工程である請求項4〜8のいずれかに記載の被覆部材の製造方法。 The said nitriding process process is a process of nitriding at 350-600 degreeC, The manufacturing method of the coating | coated member in any one of Claims 4-8 .
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