JPH10265932A - Improvement of fatigue strength of metallic member, and metallic member improved in fatigue strength - Google Patents
Improvement of fatigue strength of metallic member, and metallic member improved in fatigue strengthInfo
- Publication number
- JPH10265932A JPH10265932A JP7606697A JP7606697A JPH10265932A JP H10265932 A JPH10265932 A JP H10265932A JP 7606697 A JP7606697 A JP 7606697A JP 7606697 A JP7606697 A JP 7606697A JP H10265932 A JPH10265932 A JP H10265932A
- Authority
- JP
- Japan
- Prior art keywords
- sprayed layer
- sprayed
- fatigue strength
- metal member
- thermal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Coating By Spraying Or Casting (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、金属部材の疲労強
度向上方法、及び、疲労強度が向上した金属部材に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the fatigue strength of a metal member and to a metal member having improved fatigue strength.
【０００２】[0002]
【従来の技術】金属部材の疲労強度を向上させる方法と
して、従来より、窒化、浸炭焼入、高周波焼入等の表面
硬化法、ショットやグリッド等を投射するピーニング加
工法を実行し、金属部材の表層に残留圧縮応力を付与す
ることが行われている。2. Description of the Related Art Conventionally, as a method for improving the fatigue strength of a metal member, a surface hardening method such as nitriding, carburizing and quenching, and induction hardening, and a peening method for projecting a shot or a grid have been performed. Is applied a residual compressive stress to the surface layer.
【０００３】[0003]
【発明が解決しようとする課題】本発明は上記した方法
とは異なる方法により、疲労強度を向上させ得る金属部
材の疲金属部材の疲労強度向上方法及び疲労強度が向上
した金属部材を提供するにある。SUMMARY OF THE INVENTION The present invention provides a method for improving the fatigue strength of a metal member capable of improving the fatigue strength by a method different from the above-described method, and a metal member having an improved fatigue strength. is there.
【０００４】[0004]
【課題を解決するための手段】本発明者は上記した課題
のもとに鋭意開発を進め、そして、変態により体積膨張
する金属材料を溶射して金属部材の表面に溶射層を形成
し、溶射層の冷却による収縮よりも、変態による体積膨
張を大きくすれば、溶射層に圧縮残留応力を付与でき、
これにより金属部材の疲労強度が改善できることを知見
し、試験で確認し、本発明を完成した。SUMMARY OF THE INVENTION The present inventor has been diligently developed based on the above-mentioned problems, and sprays a metal material which expands in volume by transformation to form a sprayed layer on the surface of the metal member. If the volume expansion due to transformation is larger than the shrinkage due to cooling of the layer, compressive residual stress can be applied to the sprayed layer,
It was found that the fatigue strength of the metal member could be improved by this, and it was confirmed by a test, and the present invention was completed.
【０００５】即ち、請求項１に係る金属部材の疲労強度
向上方法は、変態により体積膨張する金属材料を用い、
金属材料を溶射して金属部材の表面に溶射層を積層し、
溶射層の冷却による収縮よりも、変態による体積膨張を
大きくすることにより、溶射層に圧縮残留応力が存在す
る部位を形成し、金属部材の疲労強度を向上させること
を特徴とするものである。That is, a method for improving the fatigue strength of a metal member according to claim 1 uses a metal material which expands in volume by transformation.
Spraying a metal material, laminating a sprayed layer on the surface of the metal member,
By increasing the volume expansion due to transformation rather than shrinkage due to cooling of the sprayed layer, a portion where compressive residual stress exists in the sprayed layer is formed, and the fatigue strength of the metal member is improved.
【０００６】請求項２に係る金属部材の疲労強度向上方
法は、請求項１において、溶射される金属材料は冷却に
伴いマルテンサイト変態する組成であることを特徴とす
るものである。請求項３に係る金属部材の疲労強度向上
方法は、請求項２において、溶射される金属材料は、重
量比で炭素を０．３〜２．０％を含むＦｅ−Ｃ系である
ことを特徴とするものである。According to a second aspect of the present invention, there is provided a method for improving the fatigue strength of a metal member according to the first aspect, wherein the metal material to be sprayed has a composition that undergoes martensitic transformation with cooling. The method for improving the fatigue strength of a metal member according to claim 3 is characterized in that, in claim 2, the metal material to be sprayed is an Fe—C-based material containing 0.3 to 2.0% of carbon by weight. It is assumed that.
【０００７】請求項４に係る金属部材の疲労強度向上方
法は、請求項２において、溶射後に溶射層に対してサブ
ゼロ処理を実行し、溶射層における残留オーステナイト
のマルテンサイト化を図ることを特徴とするものであ
る。請求項５に係る疲労強度が向上した金属部材は、変
態により体積膨張する金属材料を母材とする溶射層を有
し、溶射層は圧縮残留応力が存在する部位を備えている
ことを特徴とするものである。According to a fourth aspect of the present invention, there is provided a method for improving fatigue strength of a metal member according to the second aspect, wherein a sub-zero treatment is performed on the thermal sprayed layer after thermal spraying to convert retained austenite into martensite in the thermal sprayed layer. Is what you do. The metal member with improved fatigue strength according to claim 5 has a thermal sprayed layer whose base material is a metal material that expands in volume by transformation, and the thermal sprayed layer has a portion where compressive residual stress exists. Is what you do.
【０００８】[0008]
【発明の実施の形態】溶射層では、溶射の際の冷却によ
り凝固収縮が生じたり、凝固後の冷却により冷却収縮が
生じる。この結果、一般的には、溶射層には引張残留応
力が発生する。この点請求項１に係る方法によれば、溶
射層の冷却による収縮よりも、変態による体積膨張を大
きくすることにより、溶射層に圧縮残留応力が存在する
部位を形成する。本方法では、溶射の際に未溶融または
半溶融の粒子の割合を多くすることが好ましい。このよ
うにすれば、溶射の際に溶融粒子の割合が低下するた
め、溶射層における凝固収縮量が小さくなる。よって、
溶射層の冷却による収縮量よりも、変態による体積膨張
量を大きくするのに有利となる。従って溶射層における
変態に基づく体積膨張量が確保され、溶射層に圧縮残留
応力が存在する部位を形成するのに有利となる。BEST MODE FOR CARRYING OUT THE INVENTION In a thermal sprayed layer, solidification shrinkage is caused by cooling during thermal spraying, and cooling shrinkage is caused by cooling after solidification. As a result, a tensile residual stress generally occurs in the thermal sprayed layer. In this respect, according to the method of the first aspect, by increasing the volume expansion due to the transformation rather than the contraction due to the cooling of the sprayed layer, a portion where the compressive residual stress exists in the sprayed layer is formed. In this method, it is preferable to increase the proportion of unmelted or semi-molten particles during thermal spraying. By doing so, the ratio of the molten particles at the time of thermal spraying decreases, so that the amount of solidification shrinkage in the thermal spray layer decreases. Therefore,
This is advantageous for increasing the volume expansion due to transformation, rather than the contraction due to cooling of the sprayed layer. Therefore, the volume expansion based on the transformation in the sprayed layer is secured, which is advantageous for forming a portion where the compressive residual stress exists in the sprayed layer.
【０００９】溶射層に圧縮残留応力が存在する部位が形
成されれば、その溶射層を表面に有する金属部材の疲労
強度が向上する。亀裂の進展抑制効果が高まるためと推
察される。溶射の際における未溶融または半溶融の粒子
の割合としては、金属部材の種類、溶射する金属材料に
もよるが、溶射層において占める面積率で５〜４０％程
度、特に１５〜２５％程度が好ましいと考えられる。[0009] If a portion where compressive residual stress exists is formed in the sprayed layer, the fatigue strength of the metal member having the sprayed layer on the surface is improved. It is presumed that the effect of suppressing the crack growth was enhanced. The ratio of unmelted or semi-molten particles during thermal spraying depends on the type of metal member and the metal material to be sprayed, but is preferably about 5 to 40%, particularly about 15 to 25%, in the area ratio occupied in the sprayed layer. It is considered preferable.
【００１０】面積率が５％未満では、圧縮残留応力の部
位が形成されにくい。面積率が４０％を越えると、未溶
融または半溶融の粒子の割合が過剰となり易く、溶射層
の形成が困難となり易い。溶射する金属材料としては、
つまり溶射材としては、鉄系材料を採用できるが、これ
にアルミ合金等の非鉄系材料を混合しても良い。溶射す
る金属材料としては、溶射前の状態で、平均粒径は５〜
２５０μｍ程度のものを採用できる。[0010] If the area ratio is less than 5%, it is difficult to form a site of compressive residual stress. If the area ratio exceeds 40%, the proportion of unmelted or semi-molten particles tends to be excessive, and it becomes difficult to form a sprayed layer. As the metal material to be sprayed,
That is, an iron-based material can be used as the thermal spraying material, but a non-ferrous material such as an aluminum alloy may be mixed with the ferrous material. As the metal material to be sprayed, the average particle size is 5 before spraying.
Those having a thickness of about 250 μm can be employed.
【００１１】溶射する金属材料が粉末である場合には、
平均粒径が相対的に大きい粒子（平均粒径８０〜１００
μｍ）と、平均粒径が相対的に小さい粒子（平均粒径２
０〜５０μｍ）との混合粉末を用いることができる。こ
のようにすれば、溶射層において小さな粒子に大きい粒
子が混ざり、大きい粒子が溶射層の亀裂を停留させる停
留効果を期待し易い。When the metal material to be sprayed is a powder,
Particles having a relatively large average particle diameter (average particle diameter 80 to 100)
μm) and particles having a relatively small average particle size (average particle size 2
0 to 50 μm). In this case, large particles are mixed with small particles in the thermal sprayed layer, and it is easy to expect a stopping effect in which large particles stop cracks in the thermal sprayed layer.
【００１２】溶射する金属材料は、鉄系粉末とアルミ合
金等の非鉄系粉末との混合粉末で構成できる。この場合
には、溶射前の状態で、混合粉末を１００％としたと
き、鉄系粉末は例えば２０〜６０％、特に３５〜５５％
または４５〜５０％にできるが、これに限定されるもの
ではない。本発明で用いる金属部材の材質としては、ア
ルミ合金、銅合金、マグネシウム合金等の軽合金や軟質
合金を採用できる。金属部材としては、ピストン等を採
用できる。The metal material to be sprayed can be composed of a mixed powder of an iron-based powder and a non-ferrous powder such as an aluminum alloy. In this case, when the mixed powder is set to 100% before the thermal spraying, the iron-based powder is, for example, 20 to 60%, particularly 35 to 55%.
Alternatively, it can be 45 to 50%, but is not limited thereto. As a material of the metal member used in the present invention, a light alloy or a soft alloy such as an aluminum alloy, a copper alloy, and a magnesium alloy can be adopted. A piston or the like can be adopted as the metal member.
【００１３】本発明で形成する溶射層の厚みは、金属部
材の用途、溶射層の材質等にもよるが、例えば１００〜
５０００μｍ程度、特に２００〜１０００μｍ程度、更
に２５０〜５００μｍ程度にできるが、これに限定され
るものではない。請求項２に係る方法によれば、溶射さ
れる金属材料は冷却に伴いマルテンサイト変態する組成
であるため、マルテンサイト変態による体積膨張を期待
できる。The thickness of the thermal sprayed layer formed in the present invention depends on the use of the metal member, the material of the thermal sprayed layer and the like.
The thickness can be about 5000 μm, particularly about 200 to 1000 μm, and further about 250 to 500 μm, but is not limited thereto. According to the method of claim 2, since the metal material to be sprayed has a composition that undergoes martensitic transformation with cooling, volume expansion due to martensitic transformation can be expected.
【００１４】溶射で金属部材に被着した粒子の熱は、金
属部材に直ちに伝熱されるため、粒子は急冷され、従っ
て溶射層はマルテンサイト相の割合が多くなる。金属部
材がアルミ系合金のように熱伝導率が高い材料である場
合には、一般的には、溶射された粒子は一層に急冷され
易くなり、従ってマルテンサイト相が生成され易い。請
求項３に係る方法によれば、溶射される金属材料は、重
量比で炭素を０．３〜２．０％を含むＦｅ−Ｃ系であ
り、マルテンサイト変態による体積膨張を期待するのに
有利である。炭素が０．３未満であれば、良好なる体積
膨張量を期待できない。炭素が２．０％を越えると、溶
射する金属材料が粉末の場合には、粉末生成が困難とな
る。Ｆｅ−Ｃ系のマルテンサイト相は硬質であるため、
溶射層の耐摩耗性の向上も期待できる。上記したＦｅ−
Ｃ系では、Ｃｒ、Ｍｎ、Ｓｉを含むことができる。Since the heat of the particles deposited on the metal member by thermal spraying is immediately transferred to the metal member, the particles are quenched, so that the ratio of the martensite phase in the sprayed layer increases. When the metal member is made of a material having a high thermal conductivity such as an aluminum-based alloy, generally, the sprayed particles are more likely to be rapidly cooled, so that a martensite phase is easily generated. According to the method according to the third aspect, the metal material to be sprayed is an Fe—C-based material containing 0.3 to 2.0% of carbon in a weight ratio, so that volume expansion due to martensitic transformation is expected. It is advantageous. If carbon is less than 0.3, good volume expansion cannot be expected. If the carbon content exceeds 2.0%, it becomes difficult to generate powder when the metal material to be sprayed is powder. Since the Fe-C martensite phase is hard,
An improvement in the wear resistance of the sprayed layer can also be expected. Fe-
In the C system, Cr, Mn, and Si can be included.
【００１５】文献（日本鉄鋼協会、鉄の熱処理、改訂５
版、６３ページ）によれば、マルテンサイト変態による
体積膨張量は１．６９×重量％Ｃで示されると、報告さ
れている。このように溶射される金属材料に含まれる炭
素含有量が増大すれば、体積膨張量の増加を期待でき
る。請求項４に係る方法によれば、溶射後に溶射層に対
してサブゼロ処理が実行されるため、溶射層における残
留オーステナイトのマルテンサイト化が促進される。従
って、マルテンサイト変態による体積膨張量が確保され
る。サブゼロ処理は、液体窒素、ドライアイス等の冷媒
と溶射層とを接触させることにより実行できる。References (The Iron and Steel Institute of Japan, Heat Treatment of Iron, Revised 5)
Edition, p. 63), it is reported that the volume expansion due to martensitic transformation is 1.69 ×% by weight C. If the carbon content of the metal material sprayed in this way increases, an increase in the volume expansion can be expected. According to the method of claim 4, since the sub-zero treatment is performed on the thermal sprayed layer after thermal spraying, martensitic formation of retained austenite in the thermal sprayed layer is promoted. Therefore, the volume expansion by martensitic transformation is secured. The sub-zero treatment can be performed by bringing a coolant such as liquid nitrogen or dry ice into contact with the sprayed layer.
【００１６】請求項５に係る金属部材は、請求項１〜５
で製造した疲労強度が向上した金属部材である。即ち、
この金属部材は、アルミ合金等の金属部材本体と、金属
部材本体に積層された溶射層とで構成され、溶射層は、
圧縮残留応力が存在する部位を有するものである。According to a fifth aspect of the present invention, there is provided the metal member according to the first to fifth aspects.
It is a metal member with improved fatigue strength manufactured by the above method. That is,
This metal member is composed of a metal member main body such as an aluminum alloy, and a sprayed layer laminated on the metal member main body.
It has a portion where a compressive residual stress exists.
【００１７】[0017]
【実施例】以下、本発明の実施例を試験例に従って図面
を参照して説明する。 試験片 本実施例では、ピストンの溝底部を想定し、形状係数α
が１．８３の切欠をもつ疲労試験用の試験片（ＪＩＳ−
２２７４ １号試験片に準ずる）を金属部材として用い
た。この試験片を図１に示す。試験片の基材は、アルミ
展伸材（基本組成：Ａｌ−１０ｗｔ％Ｓｉ、添加元素：
Ｃｕ、Ｍｇ、Ｍｎ、Ｆｅ、神戸製鋼：ＫＴＭ−１０）と
した。展伸材を用いたのは、鋳造欠陥による影響をなく
すためである。試験片のうち被溶射面はＲｚ＝０．５μ
ｍ以下とした。 溶射材料 溶射される金属材料である溶射材料は、鉄系粉末（平均
粒径＝４６μｍ、アトマイズ粉末）とアルミ合金系粉末
（平均粒径＝５５μｍ、アトマイズ粉末）との混合粉末
とした。混合粉末を１００％としたとき、アルミ合金系
粉末は１０ｗｔ％とした。DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings according to test examples. Test piece In this example, the shape factor α
Has a notch of 1.83 for a fatigue test (JIS-
2274 No. 1 test piece) was used as a metal member. This test piece is shown in FIG. The base material of the test piece was an aluminum wrought material (basic composition: Al-10 wt% Si, additive element:
Cu, Mg, Mn, Fe, Kobe Steel: KTM-10). The reason for using the wrought material is to eliminate the influence of casting defects. The sprayed surface of the test piece was Rz = 0.5μ
m or less. Thermal Spray Material The thermal spray material, which is a metal material to be sprayed, was a mixed powder of an iron-based powder (average particle size = 46 μm, atomized powder) and an aluminum alloy-based powder (average particle size = 55 μm, atomized powder). When the mixed powder was 100%, the aluminum alloy-based powder was 10 wt%.
【００１８】鉄系粉末の基本組成は、Ｆｅ−１ｗｔ％Ｃ
とした。アルミ合金系粉末の基本組成はＡｌ−１５ｗｔ
％Ｓｉとした。アルミ合金系粉末は、被溶射物である試
験片がアルミ合金であるため、溶射層と試験片との間に
おける熱膨張差の緩和を主眼として用いた。なお、鉄系
粉末とアルミ合金系粉末とを含む混合粉末のうち、粒子
径が同程度であれば、融点の差により、鉄系粉末よりも
アルミ合金系粉末は溶融粒子になり易いと考えられる。 溶射処理 ＨＶＯＦ（High Velosity Oxigen Fuel)溶射法を採用し
た。ＨＶＯＦ溶射法は超音速ガスフレーム溶射とも呼ば
れ、溶射粉末粒子は通常のプラズマ溶射に比較して高速
で飛行（一般的には、通常のプラズマ溶射に比較して数
倍と言われている）すると共に、溶射粉末の溶融温度が
通常のプラズマ溶射に比較して低いという特徴をもつ。
ＨＶＯＦ溶射法で溶射した溶射層は、気孔率が低く緻密
であり、密着力も大きい。図１（ａ）に示すハッチング
領域ＳＡに溶射層を形成した。図１（ｂ）は溶射層の断
面を模式的に示す。The basic composition of the iron-based powder is Fe-1 wt% C
And Basic composition of aluminum alloy powder is Al-15wt
% Si. In the aluminum alloy-based powder, since the test piece to be sprayed was an aluminum alloy, the main purpose was to reduce the difference in thermal expansion between the sprayed layer and the test piece. It should be noted that, among the mixed powders containing the iron-based powder and the aluminum alloy-based powder, if the particle diameters are substantially the same, it is considered that the aluminum alloy-based powder is more likely to become molten particles than the iron-based powder due to the difference in melting point. . Thermal spraying HVOF (High Velosity Oxigen Fuel) thermal spraying was adopted. The HVOF spraying method is also called supersonic gas flame spraying, and sprayed powder particles fly at a higher speed than ordinary plasma spraying (generally said to be several times as large as ordinary plasma spraying). And the melting temperature of the sprayed powder is lower than that of ordinary plasma spraying.
The sprayed layer sprayed by the HVOF spraying method has a low porosity, is dense, and has a high adhesion. A sprayed layer was formed in a hatched area SA shown in FIG. FIG. 1B schematically shows a cross section of the sprayed layer.
【００１９】溶射条件は次のようとした。 プロピレン：４０リットル／分 酸素：４５リットル／分 空気：８０リットル／分 溶射層の膜厚：０．５ｍｍ なお試験片の平行部全体に膜厚２ｍｍで溶射した後、膜
厚１．５ｍｍまで機械加工し、更に中央部にＵ字形の溝
を加工した。その溝の底の部分の膜厚を溶射層の膜厚と
する。The thermal spraying conditions were as follows. Propylene: 40 liter / min Oxygen: 45 liter / min Air: 80 liter / min Thickness of sprayed layer: 0.5 mm Note that after spraying the entire parallel portion of the test piece at a thickness of 2 mm, mechanically to a thickness of 1.5 mm Then, a U-shaped groove was formed in the center. The thickness at the bottom of the groove is defined as the thickness of the sprayed layer.
【００２０】なお、冶金の分野では焼入温度が高温すぎ
ると、かえって焼きがはいりにくいと言われている。こ
の点ＨＶＯＦ処理法を採用すれば、溶射粉末の温度が通
常のプラズマ溶射法に比較して低温となるため、マルテ
ンサイト変態の促進に有利と推察される。 疲労試験 溶射層を形成した試験片を用いて疲労試験を行った。こ
の試験はＪＩＳ−Ｚ２２７４に基づいて行った。試験結
果を図２に示す。図２から理解できるように、溶射層を
形成した試験片の疲労限（繰り返し数１０7 回到達試験
片の最大値で表す）は、２５０ＭＰａ程度であった。こ
の試験片の溶射層の残留応力を測定したら、圧縮応力が
約１００〜１２０ＭＰａ存在していた。In the field of metallurgy, it is said that if the quenching temperature is too high, it is rather difficult to burn. In this regard, if the HVOF treatment method is employed, the temperature of the sprayed powder is lower than that of a normal plasma spraying method, and it is presumed that this is advantageous for promoting martensitic transformation. Fatigue test A fatigue test was performed using a test piece on which a sprayed layer was formed. This test was performed based on JIS-Z2274. The test results are shown in FIG. As can be understood from FIG. 2, the fatigue limit of the test piece on which the thermal sprayed layer was formed (represented by the maximum value of the test piece that reached 10 7 repetitions) was about 250 MPa. When the residual stress of the thermal sprayed layer of this test piece was measured, the compressive stress was about 100 to 120 MPa.
【００２１】溶射層を形成していない試験片について
も、同様に疲労試験を行った。試験結果を図３に示す。
図３から理解できるように、溶射層を形成していない試
験片の疲労限は８５ＭＰａであった。更に、溶射層の厚
みを変化させた試験片について、疲労試験を行った。試
験結果を図４に示す。図４から理解できるように、溶射
層の厚みが０．１ｍｍを越えると、疲労強度の改善効果
が大きくなる。即ち試験結果によれば、溶射層の厚みが
増大するにつれて、試験片の疲労限が増加する。溶射層
の厚みが約１ｍｍのときには、疲労限は２５０ＭＰａ付
近、または、この値を越える。Fatigue tests were also performed on test pieces having no thermal spray layer formed thereon. The test results are shown in FIG.
As can be understood from FIG. 3, the fatigue limit of the test piece having no sprayed layer was 85 MPa. Further, a fatigue test was performed on a test piece in which the thickness of the sprayed layer was changed. The test results are shown in FIG. As can be understood from FIG. 4, when the thickness of the sprayed layer exceeds 0.1 mm, the effect of improving the fatigue strength is increased. That is, according to the test results, the fatigue limit of the test piece increases as the thickness of the sprayed layer increases. When the thickness of the sprayed layer is about 1 mm, the fatigue limit is around 250 MPa or exceeds this value.
【００２２】試験片に係る溶射層を調べたところ、溶射
層を構成する粒子のうち、偏平化が進行していない粒子
は、溶射層のうち面積率で１２％〜２８％程度、特に２
０％程度であった。溶射される金属材料のうち溶射の際
に溶融化が大きく進行した粒子は、被溶射面への衝突に
より偏平化が進行し易い。このことから、偏平化が進行
していない粒子は、溶射の際において未溶融または半溶
融の粒子であると推察される。 サブゼロ処理 溶射層を形成した試験片に対して、サブゼロ処理を実行
した。この試験では前記した条件と同様な溶射条件で、
溶射層（厚み：０．５ｍｍ）を形成した。溶射粉末は前
記同様に鉄系粉末とアルミ合金系粉末とで構成されてい
る。但し鉄系粉末の組成は、Ｆｅ−１．５ｗｔ％Ｃとし
た。試験片に係る溶射層を調べたところ、偏平化が進行
していない粒子は、面積率で１０％〜２８％程度、特に
２０％程度であった。Examination of the sprayed layer of the test piece revealed that, among the particles constituting the sprayed layer, particles whose flattening had not progressed had an area ratio of about 12% to 28%, particularly 2%, in the sprayed layer.
It was about 0%. Among the metal materials to be sprayed, particles that have greatly advanced in melting during thermal spraying tend to flatten due to collision with the surface to be sprayed. From this, it is inferred that particles that have not been flattened are unmelted or semi-molten particles during thermal spraying. Sub-zero treatment Sub-zero treatment was performed on the test piece on which the sprayed layer was formed. In this test, under the same spraying conditions as above,
A sprayed layer (thickness: 0.5 mm) was formed. The thermal spray powder is composed of an iron-based powder and an aluminum alloy-based powder as described above. However, the composition of the iron-based powder was Fe-1.5 wt% C. When the sprayed layer of the test piece was examined, the particles in which flattening had not progressed were about 10% to 28%, particularly about 20% in area ratio.
【００２３】このような溶射層を形成した試験片を液体
窒素（７７Ｋ）に５分間浸漬し、サブゼロ処理を実行し
た。そして、サブゼロ処理前の試験片、サブゼロ処理後
の試験片の双方について、同様に疲労試験を行った。試
験結果を図５に示す。サブゼロ処理前の試験片の疲労限
は２１０ＭＰａ程度であり、サブゼロ処理前の溶射層に
は残留オーステナイトが面積率で２５％程度存在してい
た。これに対してサブゼロ処理後の試験片の疲労限は、
２８０ＭＰａ程度に上昇した。この値は鋼材に匹敵する
と考えられる。 面積率と応力との関係 溶射層における未溶融または半溶融の粒子の面積率と溶
射層における残留応力との関係について、試験した。試
験条件は前記したものと同様である。但し、鉄系粉末
は、平均粒径が６０μｍの第１粉末と、平均粒径が２８
μｍの第２粉末とを混ぜて用いた。大径の粉末粒子は熱
容量が大きく、溶射の際に未溶融または半溶融になり易
いことから、第１粉末と第２粉末との割合を調整するこ
とにより、未溶融または半溶融の粒子の面積率を変化で
きるからである。The test piece on which such a sprayed layer was formed was immersed in liquid nitrogen (77 K) for 5 minutes to perform a sub-zero treatment. Then, a fatigue test was similarly performed on both the test piece before the sub-zero treatment and the test piece after the sub-zero treatment. The test results are shown in FIG. The fatigue limit of the test piece before the sub-zero treatment was about 210 MPa, and the sprayed layer before the sub-zero treatment had a retained austenite in an area ratio of about 25%. On the other hand, the fatigue limit of the test piece after sub-zero treatment is
It increased to about 280 MPa. This value is considered to be comparable to steel. Relationship between Area Ratio and Stress The relationship between the area ratio of unmelted or semi-molten particles in the sprayed layer and the residual stress in the sprayed layer was tested. The test conditions are the same as described above. However, the iron-based powder has a first powder having an average particle size of 60 μm and an average particle size of 28 μm.
μm of a second powder was used. Since large-diameter powder particles have a large heat capacity and tend to be unmelted or semi-molten during thermal spraying, the area of unmelted or semi-molten particles is adjusted by adjusting the ratio of the first powder and the second powder. This is because the rate can be changed.
【００２４】この試験では、溶射層において未溶融また
は半溶融の粒子が占める面積率は、次のようして規定し
た。即ち、溶射層の顕微鏡写真を利用し、粒子のアスペ
クト比Ａ（長径／短径）が３未満のもの（Ａ＜３）を、
未溶融または半溶融の粒子とみなし、これの面積率を画
像処理で求めた。残留応力は前述同様にＸ線にて測定し
た。In this test, the area ratio occupied by unmelted or semi-molten particles in the sprayed layer was defined as follows. That is, using the micrograph of the sprayed layer, the particles having an aspect ratio A (major axis / minor axis) of less than 3 (A <3),
The particles were regarded as unmelted or semi-molten particles, and their area ratio was determined by image processing. The residual stress was measured by X-ray as described above.
【００２５】試験結果を図６に示す。図６から理解でき
るように、未溶融または半溶融の粒子の面積率が大きく
なるにつれて、溶射層における圧縮残留応力が増大する
傾向となる。未溶融または半溶融の粒子が占める面積率
が大きいと、凝固収縮量が小さくなる。そのため、凝固
収縮量よりも体積膨張量が大きくなり易く、圧縮残留応
力が増大するものと推察される。FIG. 6 shows the test results. As can be understood from FIG. 6, the compressive residual stress in the sprayed layer tends to increase as the area ratio of the unmelted or semi-molten particles increases. When the area ratio occupied by unmelted or semi-molten particles is large, the amount of solidification shrinkage becomes small. Therefore, it is presumed that the volume expansion tends to be larger than the solidification shrinkage, and the compressive residual stress increases.
【００２６】なおこの試験では、残留応力が１８０ＭＰ
ａの引張であった試験片を除いて、ＨＶＯＦ法により溶
射層を形成した。 面積率と疲労強度との関係 溶射層の厚みを０．５ｍｍに設定した状態で、未溶融ま
たは半溶融の粒子の面積率と試験片の疲労強度との関係
について試験し、試験結果を図７に示す。図７に示すよ
うに、未溶融または半溶融の粒子の面積率が増加するに
つれて、試験片の疲労限が増加する。面積率が２０〜４
０％では疲労限は２５０ＭＰａ程度となる。 面積率と溶射付着効率との関係 未溶融または半溶融の粒子の面積率と溶射付着効率との
関係について試験し、試験結果を図８に示す。図８に示
すように、未溶融または半溶融の粒子の面積率が増加す
るにつれて、溶射粉末の付着効率が低下する傾向があ
る。溶射の際に、未溶融または半溶融の粒子の割合が増
加すれば、溶射される粒子の溶融が不充分となり、被溶
射面に付着しにくくなるからである。 適用例 図９〜図１０は適用例を示す。この例では、ガソリン用
またはディーゼル用の内燃機関に使用するアルミ合金
（Ａｌ−Ｓｉ系）で形成したピストン１には、溶射処理
前にはリング状の溝１１が形成されている。この溝１１
は、傾斜角θ１をもつ傾斜面１１ａと、底面１１ｃとを
もつ。In this test, the residual stress was 180MP.
A thermal spray layer was formed by the HVOF method except for the test piece which was tensile in a. Relationship between area ratio and fatigue strength With the thickness of the sprayed layer set to 0.5 mm, the relationship between the area ratio of unmelted or semi-molten particles and the fatigue strength of the test piece was tested. Shown in As shown in FIG. 7, as the area ratio of unmelted or semi-molten particles increases, the fatigue limit of the test piece increases. Area ratio is 20-4
At 0%, the fatigue limit is about 250 MPa. Relationship between Area Ratio and Thermal Spray Adhesion Efficiency The relationship between the area ratio of unmelted or semi-molten particles and the thermal spray adhesion efficiency was tested, and the test results are shown in FIG. As shown in FIG. 8, as the area ratio of unmelted or semi-molten particles increases, the adhesion efficiency of the sprayed powder tends to decrease. This is because if the ratio of unmelted or semi-molten particles increases during thermal spraying, the particles to be sprayed will not be sufficiently melted and will not easily adhere to the surface to be sprayed. Application Examples FIGS. 9 and 10 show application examples. In this example, a ring-shaped groove 11 is formed in a piston 1 formed of an aluminum alloy (Al-Si system) used for a gasoline or diesel internal combustion engine before thermal spraying. This groove 11
Has an inclined surface 11a having an inclination angle θ1 and a bottom surface 11c.
【００２７】そして溶射ガン４により、溶射粉末を矢印
Ａ１方向に噴出し、ピストン１の溝１１に溶射層２を積
層し、溶射処理（ＨＶＯＦ処理）した。その後、溶射層
２に切削加工を施し、ピストンリング溝３を形成した。
ピストンリング溝３は、ピストンリングと摺動する摺動
面３１、３２と底面３３とをもつ。この溶射層２に対し
ても前述同様にサブゼロ処理を施すことができる。Then, the thermal spray powder was sprayed in the direction of arrow A1 by the thermal spray gun 4, the thermal spray layer 2 was laminated on the groove 11 of the piston 1, and thermal spraying (HVOF) was performed. Thereafter, the sprayed layer 2 was subjected to cutting to form the piston ring groove 3.
The piston ring groove 3 has sliding surfaces 31 and 32 that slide on the piston ring and a bottom surface 33. The sub-zero treatment can be applied to the thermal sprayed layer 2 as described above.
【００２８】溝１１の傾斜面１１ａ及び底面１１ｃは拘
束面として機能し得るため、溝１１に積層された溶射層
２は拘束性が高い。そのため、サブゼロ処理により溶射
層２におけるマルテンサイト化が促進されて、溶射層２
における体積膨張量が増加すると、溶射層２における圧
縮残留応力の増加を期待できる。 （他の例）上記した記載から次の技術的思想も把握でき
る。 ○金属部材は拘束面をもち、拘束面付近に溶射層が形成
されていることを特徴とする各請求項に係る疲労強度向
上方法及び部材 ○金属部材本体に溶射層を積層して構成され、溶射層は
圧縮残留応力が存在する部位を有することを特徴とする
疲労強度が向上した金属部材。 ○変態により体積膨張する金属材料と、溝をもつピスト
ンとを用い、前記金属材料を溶射してピストンの溝に溶
射層を積層し、前記溶射層の冷却による収縮よりも、変
態による体積膨張を大きくすることにより、前記溶射層
に圧縮残留応力が存在する部位を形成することを特徴と
するピストンの溝の疲労強度向上方法及びピストン。Since the inclined surface 11a and the bottom surface 11c of the groove 11 can function as a constraining surface, the thermal sprayed layer 2 laminated on the groove 11 has a high constraining property. Therefore, the formation of martensite in the thermal spray layer 2 is promoted by the sub-zero treatment, and the thermal spray layer 2
When the volume expansion amount of the thermal spray layer 2 increases, an increase in the compressive residual stress in the thermal sprayed layer 2 can be expected. (Other Examples) The following technical ideas can be understood from the above description. ○ The metal member has a constrained surface, the fatigue strength improving method and the member according to each claim characterized in that a sprayed layer is formed near the constrained surface ○ The metal member body is formed by laminating a sprayed layer, A metal member having improved fatigue strength, characterized in that the thermal sprayed layer has a portion where compressive residual stress exists. ○ Using a metal material that expands in volume by transformation and a piston having a groove, the metal material is sprayed to deposit a sprayed layer in the groove of the piston, and the volume expansion due to transformation is reduced rather than shrinkage due to cooling of the sprayed layer. A method for improving the fatigue strength of a groove of a piston, wherein a portion where a compressive residual stress exists in the sprayed layer is formed by increasing the size.
【００２９】[0029]
【発明の効果】請求項１に係る疲労強度向上方法によれ
ば、溶射層の冷却による収縮よりも変態による体積膨張
を大きくすることにより、溶射層に圧縮残留応力が存在
する部位を形成する。そのため金属部材の疲労強度が改
善される。請求項２に係る疲労強度向上方法によれば、
溶射される金属材料は冷却に伴いマルテンサイト変態す
る組成であるため、溶射層の冷却による収縮よりも、変
態による体積膨張を大きくするのに有利である。そのた
め金属部材の疲労強度を改善するのに有利である。According to the method for improving fatigue strength according to the first aspect, by increasing the volume expansion due to the transformation rather than the contraction due to cooling of the sprayed layer, a portion where the compressive residual stress exists in the sprayed layer is formed. Therefore, the fatigue strength of the metal member is improved. According to the fatigue strength improving method according to claim 2,
Since the metal material to be sprayed has a composition that undergoes martensitic transformation with cooling, it is advantageous to increase the volume expansion due to transformation rather than shrinkage due to cooling of the sprayed layer. Therefore, it is advantageous for improving the fatigue strength of the metal member.
【００３０】請求項３に係る疲労強度向上方法によれ
ば、溶射される金属材料は、重量比で炭素を０．３〜
２．０％を含むＦｅ−Ｃ系であるため、良好なるマルテ
ンサイト変態が得られる。そのため金属部材の疲労強度
を改善するのに有利である。Ｆｅ−Ｃ系のマルテンサイ
ト相は硬質であるため、溶射層の耐摩耗性の向上も期待
できる。請求項４に係る疲労強度向上方法によれば、溶
射後に溶射層に対してサブゼロ処理を実行し、溶射層に
おける残留オーステナイトのマルテンサイト化を図る。
そのため、マルテンサイト化が促進され、溶射層の冷却
による収縮よりも変態による体積膨張を大きくするのに
有利である。そのため金属部材の疲労強度を改善するの
に有利である。According to the third aspect of the present invention, the metal material to be sprayed contains carbon in a weight ratio of 0.3 to 0.3.
Since it is an Fe-C system containing 2.0%, good martensitic transformation can be obtained. Therefore, it is advantageous for improving the fatigue strength of the metal member. Since the Fe-C-based martensite phase is hard, an improvement in the wear resistance of the sprayed layer can be expected. According to the method for improving fatigue strength according to the fourth aspect, a sub-zero treatment is performed on the thermal sprayed layer after thermal spraying, and martensite of retained austenite in the thermal sprayed layer is achieved.
Therefore, the formation of martensite is promoted, which is advantageous for increasing the volume expansion due to the transformation rather than the contraction due to cooling of the sprayed layer. Therefore, it is advantageous for improving the fatigue strength of the metal member.
【００３１】請求項５に係る金属部材によれば、疲労強
度が向上するため、耐久性が向上し、長寿命化に有利で
ある。According to the metal member according to the fifth aspect, since the fatigue strength is improved, the durability is improved, which is advantageous for extending the life.
【図１】試験片の正面図である。FIG. 1 is a front view of a test piece.
【図２】溶射層を形成した試験片の疲労試験の結果を示
すグラフである。FIG. 2 is a graph showing a result of a fatigue test of a test piece on which a sprayed layer is formed.
【図３】溶射層を形成していない試験片の疲労試験の結
果を示すグラフである。FIG. 3 is a graph showing a result of a fatigue test of a test piece having no thermal sprayed layer formed thereon.
【図４】溶射層を形成した試験片の疲労限と溶射層の厚
みとの関係を示すグラフである。FIG. 4 is a graph showing a relationship between a fatigue limit of a test piece on which a sprayed layer is formed and a thickness of the sprayed layer.
【図５】サブゼロ処理を実行する前と実行した後におけ
る試験片の疲労限を示すグラフである。FIG. 5 is a graph showing a fatigue limit of a test piece before and after execution of a sub-zero process.
【図６】未溶融または半溶融の粒子の面積率と残留応力
との関係を示すグラフである。FIG. 6 is a graph showing the relationship between the area ratio of unmelted or semi-molten particles and residual stress.
【図７】未溶融または半溶融の粒子の面積率と試験片の
疲労限との関係を示すグラフである。FIG. 7 is a graph showing a relationship between an area ratio of unmelted or semi-molten particles and a fatigue limit of a test piece.
【図８】未溶融または半溶融の粒子の面積率と溶射付着
効率との関係を示すグラフである。FIG. 8 is a graph showing the relationship between the area ratio of unmelted or semi-molten particles and the thermal spray deposition efficiency.
【図９】ピストンの溝に溶射層を形成する際の工程図で
ある。FIG. 9 is a process chart when a sprayed layer is formed in a groove of a piston.
【図１０】ピストンの溝に形成した溶射層付近の断面図
である。FIG. 10 is a sectional view of the vicinity of a sprayed layer formed in a groove of a piston.
図中、１はピストン（金属部材）、２は溶射層を示す。 In the figure, 1 indicates a piston (metal member) and 2 indicates a sprayed layer.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 中野 敬章 愛知県刈谷市朝日町２丁目１番地 アイシ ン精機株式会社内 (72)発明者 恒川 浩一 愛知県刈谷市朝日町２丁目１番地 アイシ ン精機株式会社内 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keisho Nakano 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Koichi Tsunekawa 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Inside the corporation
Claims (5)
前記金属材料を溶射して金属部材の表面に溶射層を積層
し、前記溶射層の冷却による収縮よりも、変態による体
積膨張を大きくすることにより、前記溶射層に圧縮残留
応力が存在する部位を形成し、前記金属部材の疲労強度
を向上させることを特徴とする金属部材の疲労強度向上
方法。1. A metal material that expands in volume by transformation,
By spraying the metal material and laminating a sprayed layer on the surface of the metal member, by shrinking the sprayed layer by cooling, by increasing the volume expansion due to transformation, the portion where the compressive residual stress is present in the sprayed layer. Forming a metal member to improve the fatigue strength of the metal member.
料は冷却に伴いマルテンサイト変態する組成であること
を特徴とする金属部材の疲労強度向上方法。2. The method for improving the fatigue strength of a metal member according to claim 1, wherein the metal material to be sprayed has a composition that undergoes martensitic transformation with cooling.
料は、重量比で炭素を０．３〜２．０％を含むＦｅ−Ｃ
系であることを特徴とする金属部材の疲労強度向上方
法。3. The metal material to be sprayed according to claim 2, wherein the metal material to be sprayed contains Fe-C containing 0.3 to 2.0% by weight of carbon.
A method for improving the fatigue strength of a metal member, characterized by being a system.
対してサブゼロ処理を実行し、前記溶射層における残留
オーステナイトのマルテンサイト化を図ることを特徴と
する金属部材の疲労強度向上方法。4. The method for improving the fatigue strength of a metal member according to claim 2, wherein a sub-zero treatment is performed on the thermal sprayed layer after thermal spraying to convert retained austenite into martensite in the thermal sprayed layer.
する溶射層を有し、前記溶射層は圧縮残留応力が存在す
る部位を備えていることを特徴とする疲労強度が向上し
た金属部材。5. A metal member having improved fatigue strength, comprising: a sprayed layer having a base material of a metal material which expands in volume by transformation, wherein the sprayed layer has a portion where a compressive residual stress exists. .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07606697A JP3383179B2 (en) | 1997-03-27 | 1997-03-27 | Method for improving fatigue strength of metal member and metal member having improved fatigue strength |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07606697A JP3383179B2 (en) | 1997-03-27 | 1997-03-27 | Method for improving fatigue strength of metal member and metal member having improved fatigue strength |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10265932A true JPH10265932A (en) | 1998-10-06 |
| JP3383179B2 JP3383179B2 (en) | 2003-03-04 |
Family
ID=13594415
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07606697A Expired - Fee Related JP3383179B2 (en) | 1997-03-27 | 1997-03-27 | Method for improving fatigue strength of metal member and metal member having improved fatigue strength |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3383179B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016000849A (en) * | 2014-06-11 | 2016-01-07 | 日本発條株式会社 | Production method of laminate, and laminate |
-
1997
- 1997-03-27 JP JP07606697A patent/JP3383179B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016000849A (en) * | 2014-06-11 | 2016-01-07 | 日本発條株式会社 | Production method of laminate, and laminate |
| US10315388B2 (en) | 2014-06-11 | 2019-06-11 | Nhk Spring Co., Ltd. | Method of manufacturing laminate and laminate |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3383179B2 (en) | 2003-03-04 |
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