JP6131539B2 - Degradation evaluation method for machine parts - Google Patents
Degradation evaluation method for machine parts Download PDFInfo
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- JP6131539B2 JP6131539B2 JP2012157413A JP2012157413A JP6131539B2 JP 6131539 B2 JP6131539 B2 JP 6131539B2 JP 2012157413 A JP2012157413 A JP 2012157413A JP 2012157413 A JP2012157413 A JP 2012157413A JP 6131539 B2 JP6131539 B2 JP 6131539B2
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- 238000011156 evaluation Methods 0.000 title claims description 13
- 230000015556 catabolic process Effects 0.000 title claims description 7
- 238000006731 degradation reaction Methods 0.000 title claims description 7
- 239000002244 precipitate Substances 0.000 claims description 72
- 229910000831 Steel Inorganic materials 0.000 claims description 56
- 239000010959 steel Substances 0.000 claims description 56
- 229910001068 laves phase Inorganic materials 0.000 claims description 40
- 230000006866 deterioration Effects 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 32
- 238000003384 imaging method Methods 0.000 claims description 9
- 238000010586 diagram Methods 0.000 claims description 7
- 238000000605 extraction Methods 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 238000005728 strengthening Methods 0.000 description 7
- 239000007788 liquid Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 239000006061 abrasive grain Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- Testing Of Devices, Machine Parts, Or Other Structures Thereof (AREA)
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Investigating And Analyzing Materials By Characteristic Methods (AREA)
Description
本発明は、タービン部品などの機械部品の劣化を評価する方法に関し、特に、高Ｃｒ鋼などの耐熱鋼からなる機械部品の劣化評価方法に関する。 The present invention relates to a method for evaluating deterioration of a machine part such as a turbine part, and more particularly to a method for evaluating deterioration of a machine part made of heat-resistant steel such as high Cr steel.
一般に、火力発電所で使用される蒸気タービンは、高温高圧の環境下で使用される。このため、ロータ、ケーシング、配管などのタービン部品は耐熱鋼からなるものが使用され、特に主蒸気温度が６００℃級のＵＳＣ機（超々臨界圧発電機）では、９質量％〜１２質量％のＣｒを含有する高Ｃｒ鋼がタービン部品の材料として使用されている。
高Ｃｒ鋼は鋼組織がマルテンサイト組織であり、モリブデン（Ｍｏ）やタングステン（Ｗ）などによる固溶強化、金属間化合物であるラーベス相やＭＸ炭窒化物の分散強化・析出強化、ホウ素（Ｂ）による粒界強化といった様々な組織強化法によって優れた高温強度を有している。
Generally, a steam turbine used in a thermal power plant is used in a high temperature and high pressure environment. For this reason, turbine parts such as rotors, casings, and piping are made of heat-resistant steel. Especially in USC machines (super super critical pressure generators) having a main steam temperature of 600 ° C., they are 9% by mass to 12% by mass. High Cr steel containing Cr is used as a material for turbine parts.
High Cr steel has a martensitic steel structure, solid solution strengthening with molybdenum (Mo), tungsten (W), etc., dispersion strengthening / precipitation strengthening of Laves phase and MX carbonitride which are intermetallic compounds, boron (B ) Has excellent high temperature strength by various structure strengthening methods such as grain boundary strengthening.
しかし、高Ｃｒ鋼からなるタービン部品を高温、高応力の環境下で長時間使用すると、ＭｏやＷなどの固溶強化元素がラーベス相あるいは炭窒化物などの析出物となってタービン部品の鋼組織に析出する。そして、析出した析出物が結晶粒界やマルテンサイトラス境界に凝集・粗大化すると材料の強度低下を招き、析出物の凝集・粗大箇所がクリープ損傷の主要因であるボイドの発生箇所や亀裂の起点となりやすい。 However, when turbine parts made of high-Cr steel are used for a long time in a high-temperature, high-stress environment, solid solution strengthening elements such as Mo and W become precipitates such as Laves phases or carbonitrides, resulting in steel for turbine parts. It precipitates in the structure. When the deposited precipitates agglomerate and coarsen at the grain boundaries and martensite lath boundaries, the strength of the material is reduced. It is easy to become.
このような材料劣化がタービン部品に生じるとタービン部品の破損に至るため、クリープ、脆性、疲労などの劣化度や損傷度を非破壊で高精度に評価することでタービン部品の余寿命を算出し、破損に至る前にタービン部品の保守管理を行う必要がある。
高Ｃｒ鋼などの耐熱鋼からなるタービン部品の劣化を評価する方法としては、耐熱鋼の表面に析出した析出物の面積率または耐熱鋼の表面に発生したボイドの個数密度を算出し、その算出値を基にタービン部品の劣化を評価する方法が知られている（例えば、特許文献１参照）。
When such material deterioration occurs in turbine parts, the turbine parts are damaged. Therefore, the remaining life of turbine parts is calculated by nondestructively evaluating the degree of deterioration and damage such as creep, brittleness and fatigue. It is necessary to perform maintenance management of turbine parts before they are damaged.
As a method of evaluating the deterioration of turbine parts made of heat-resistant steel such as high Cr steel, the area ratio of precipitates deposited on the surface of the heat-resistant steel or the number density of voids generated on the surface of the heat-resistant steel is calculated and the calculation is performed. A method for evaluating deterioration of a turbine component based on a value is known (see, for example, Patent Document 1).
しかしながら、析出物の面積率は、図７に示すように、析出物の検出箇所によって異なる値となり、析出物の面積率を劣化の指標値とした場合には、指標値にバラツキが生じる。なお、図７（ａ）（析出物面積率８１％）および図７（ｂ）（析出物面積率１０．６％）は、同じサンプルにおける異なる検出箇所について測定した析出物の反射電子像を同じ拡大率で示す図である。また、耐熱鋼表面に析出する析出物のうちラーベス相は、Ｍ２３Ｃ６やＭＸ炭窒化物などの析出物と比較して、応力依存性が低い。このため、ラーベス相を含む析出物の面積率を劣化指標値にすると、析出物の面積率を指標値とする耐熱鋼のクリープ損傷評価曲線が図８に示すようなクリープ損傷評価曲線となり、応力が負荷される場合の劣化と応力が負荷されない場合の劣化とを区別して評価することが困難となる。従って、ラーベス相を含む析出物の面積率からタービン部品の劣化を評価する方法では、高応力が負荷されるタービン部品の劣化を正確に評価できないという問題がある。 However, as shown in FIG. 7, the area ratio of the precipitate varies depending on the detected position of the precipitate. When the area ratio of the precipitate is used as an index value for deterioration, the index value varies. 7A (precipitate area ratio 81%) and FIG. 7B (precipitate area ratio 10.6%) are the same as the reflected electron images of the precipitates measured at different detection locations in the same sample. It is a figure shown by an expansion rate. In addition, Laves phase out of the precipitates precipitated on the surface of the heat resistant steel is less stress-dependent than precipitates such as M23C6 and MX carbonitride. For this reason, when the area ratio of the precipitate containing Laves phase is used as the degradation index value, the creep damage evaluation curve of the heat resistant steel with the area ratio of the precipitate as the index value becomes a creep damage evaluation curve as shown in FIG. It is difficult to distinguish and evaluate the deterioration when the load is applied and the deterioration when the stress is not applied. Therefore, the method for evaluating the deterioration of the turbine component from the area ratio of the precipitate containing the Laves phase has a problem that the deterioration of the turbine component to which a high stress is applied cannot be accurately evaluated.
また、５６６℃級タービンの構成部材であるＣｒＭｏＶ鋼では、主としてＭ２３Ｃ６、ＭＣ、ＭＸ窒化物などの析出物が生成され、損傷率５０％程度からボイドの発生が認められるが、６００℃級タービンの構成部材である高Ｃｒ鋼では、材料強化因子が複雑であり、寿命末期でないとボイドが発生しない。このため、ボイドの個数密度からタービン部品の劣化を評価しても、高応力が負荷されるタービン部品の劣化を正確に評価できないという問題がある。
本発明は、上述した問題点に鑑みてなされたもので、使用条件が高温・高応力下であっても耐熱鋼からなる機械部品の劣化を正確に評価することのできる機械部品の劣化評価方法を提供することを目的とするものである。
In addition, in CrMoV steel, which is a component of a 566 ° C class turbine, precipitates such as M23C6, MC, MX nitride are mainly generated, and voids are observed from a damage rate of about 50%. In the high Cr steel which is a constituent member, the material strengthening factor is complicated, and voids are not generated unless it is at the end of life. For this reason, even if the deterioration of the turbine component is evaluated from the number density of the voids, there is a problem that the deterioration of the turbine component to which a high stress is applied cannot be accurately evaluated.
The present invention has been made in view of the above-mentioned problems, and a deterioration evaluation method for machine parts that can accurately evaluate the deterioration of machine parts made of heat-resistant steel even when the use conditions are high temperature and high stress. Is intended to provide.
上記課題を解決するために、本発明は、耐熱鋼からなる機械部品の劣化を評価する方法であって、前記機械部品の鋼組織に析出した析出物のレプリカを抽出レプリカ法により作成し、次いで前記レプリカを電子顕微鏡により撮像して前記析出物の反射電子像を得た後、得られた反射電子像の明度から前記析出物をラーベス相とラーベス相以外の析出物とに分類し、次いで前記ラーベス相以外の析出物１個当りの平均面積を求め、該平均面積を指標値とする耐熱鋼のクリープ損傷度をラーソン・ミラー・パラメータ（ＬＭＰ）線図から求め、前記クリープ損傷度をＰｒ、前記ラーソン・ミラー・パラメータ（ＬＭＰ）線図においてクリープ損傷曲線Ｃ１がクリープ破断曲線Ｃ２と交わる点のラーソン・ミラー・パラメータ（ＬＭＰ）をＰｃ、耐熱鋼の使用温度をＴ（℃）、使用時間をｔ（ｈ）として、クリープ損傷寿命Ｔｆを
Ｔｆ＝（10 ((Pc-Pr)・100/T) -1）ｔ
で求めて前記機械部品の劣化を評価することを特徴とする。
In order to solve the above-mentioned problems, the present invention is a method for evaluating deterioration of a machine part made of heat-resistant steel, wherein a replica of a precipitate precipitated in the steel structure of the machine part is created by an extraction replica method, and then After obtaining the reflected electron image of the precipitate by imaging the replica with an electron microscope, the precipitate is classified into Laves phase and precipitates other than Laves phase from the brightness of the obtained reflected electron image, The average area per precipitate other than the Laves phase is obtained, the creep damage degree of the heat-resistant steel with the average area as an index value is obtained from a Larson-Miller parameter (LMP) diagram , and the creep damage degree is determined as Pr, In the Larson Miller parameter (LMP) diagram, the Larson Miller parameter (LMP) at the point where the creep damage curve C1 intersects the creep rupture curve C2 is defined as Pc, The working temperature of the steel T (° C.), the use time as t (h), the creep damage life Tf
Tf = (10 ((Pc-Pr) · 100 / T) −1) t
In determined and evaluating the deterioration of the mechanical parts.
本発明において、前記電子顕微鏡の観察視野が耐熱鋼の結晶粒界を含む視野となるように前記レプリカを電子顕微鏡により撮像して反射電子像を得ることが好ましい。
また、前記ラーベス相以外の析出物のうちＭ２３Ｃ６の１個当りの平均面積を求め、該平均面積を指標値とする耐熱鋼のクリープ損傷度を求めて前記機械部品の劣化を評価することが好ましい。
In the present invention, it is preferable to obtain a reflected electron image by imaging the replica with an electron microscope so that the observation field of view of the electron microscope becomes a field of view including a grain boundary of heat-resistant steel.
The front Symbol obtain an average area per the M23C6 of Laves other than phase precipitates, be seeking creep damage of the heat-resisting steel is used as an index value to the average area to evaluate the degradation of the mechanical component preferable.
本発明では、機械部品の劣化を評価する際に応力依存性の低いラーベス相を除外できると共に、応力が負荷される場合の劣化と応力が負荷されない場合の劣化とを区別して評価することが可能となる。従って、使用条件が高温・高応力下であっても耐熱鋼からなる機械部品の劣化を正確に評価することができる。 In the present invention, Laves phases with low stress dependency can be excluded when evaluating deterioration of machine parts, and it is possible to distinguish and evaluate deterioration when stress is applied and deterioration when stress is not applied. It becomes. Therefore, it is possible to accurately evaluate the deterioration of mechanical parts made of heat-resistant steel even when the use conditions are high temperature and high stress.
以下、図面を参照して本発明の一実施の形態について説明する。
本発明の一実施形態に係る機械部品の劣化評価方法を説明するための工程図を図１に示す。本発明の一実施形態に係る機械部品の劣化評価方法は、図１に示すように、レプリカ作成工程Ｓ１、反射電子像取得工程Ｓ２、析出物分類工程Ｓ３、平均面積算出工程Ｓ４、クリープ損傷度算出工程Ｓ５、余寿命算出工程Ｓ６および余寿命率算出工程Ｓ７を経て機械部品の劣化を評価する方法である。
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram for explaining a deterioration evaluation method for mechanical parts according to an embodiment of the present invention. As shown in FIG. 1, the degradation evaluation method for mechanical parts according to an embodiment of the present invention includes a replica creation step S1, a reflected electron image acquisition step S2, a precipitate classification step S3, an average area calculation step S4, and a creep damage degree. This is a method for evaluating the deterioration of the machine component through the calculation step S5, the remaining life calculation step S6, and the remaining life rate calculation step S7.
（レプリカ作成工程）
レプリカ作成工程Ｓ１は耐熱鋼からなる機械部品の鋼組織に析出した析出物のレプリカを図２に示す抽出レプリカ法により作成する工程であって、具体的には、機械部品１の表面を例えば９μｍ以下のダイヤモンド砥粒でバフ研磨し、機械部品１の表面を鏡面に仕上げた後、機械部品１の表面を析出物２が明瞭となるまでエッチングする。次に、機械部品１の表面をアルコールあるいは洗浄液により洗浄した後、機械部品１の表面を乾燥させ、乾燥した機械部品１の表面上に膜厚が３μｍ以下のカーボンレプリカ膜３を蒸着する。
その後、カーボンレプリカ膜３の膜端部に２ｍｍ角程度の切り込みを入れた後、再び機械部品１の表面をエッチングする。このとき腐食液はカーボンレプリカ膜３の切り込み箇所から浸入し、切り込み箇所から浸入した腐食液によって機械部品１の鋼組織が溶け出すことにより、析出物２のみがカーボンレプリカ膜３に付着する。
(Replica creation process)
The replica creation step S1 is a step of creating a replica of precipitates precipitated in the steel structure of a machine part made of heat-resistant steel by the extraction replica method shown in FIG. 2, and specifically, the surface of the
Then, after cutting about 2 mm square in the film | membrane edge part of the carbon replica film | membrane 3, the surface of the
次に、カーボンレプリカ膜３を機械部品１の表面から剥がし、カーボンレプリカ膜３を洗浄液により洗浄する。その後、Ｃｕグリッドによりレプリカ膜を洗浄槽からすくい取り、自然乾燥させることで、析出物２のレプリカを得ることができる。
なお、カーボンレプリカ膜３を有機溶媒により洗浄する場合は、有機溶媒の濃度が高いとカーボンレプリカ膜３に曲りが生ずるため、有機溶媒の濃度を減少させた洗浄液を幾つか用意しておくことが好ましい。
Next, the carbon replica film 3 is peeled off from the surface of the
When the carbon replica film 3 is washed with an organic solvent, since the carbon replica film 3 is bent when the concentration of the organic solvent is high, it is necessary to prepare several cleaning liquids with a reduced concentration of the organic solvent. preferable.
（反射電子像取得工程）
反射電子像取得工程Ｓ２はレプリカ作成工程Ｓ１で得られた析出物２のレプリカを走査型電子顕微鏡等の電子顕微鏡により撮像して析出物２の反射電子像を得る工程であって、析出物２の反射電子像を得るときには、電子顕微鏡の撮像視野が耐熱鋼の結晶粒界を含む視野となるように析出物２のレプリカを電子顕微鏡により撮像して反射電子像を得ることが好ましい。
(Reflected electron image acquisition process)
The reflected electron image acquisition step S2 is a step of obtaining a reflected electron image of the
（析出物分類工程）
析出物分類工程Ｓ３は反射電子像取得工程Ｓ２で得られた反射電子像の明度から析出物２をラーベス相とラーベス相以外の析出物とに分類する工程であって、析出物２のレプリカを走査型電子顕微鏡等の電子顕微鏡で撮像すると、図３に示すように、ラーベス相はラーベス以外の析出物よりも明度の高い反射電子像となるので、反射電子像取得工程Ｓ２で得られた反射電子像の明度から析出物２をラーベス相とラーベス相以外の析出物とに分類することができる。なお、図３（ｂ）は図３（ａ）の中央箇所を拡大表示した図である。
(Precipitation classification process)
The precipitate classification step S3 is a step of classifying the
（平均面積算出工程）
平均面積算出工程Ｓ４はラーベス相以外の析出物１個当りの平均面積を求める工程であって、ラーベス相以外の析出物１個当りの平均面積を求める方法としては、例えば図４に示す方法を用いることができる。
具体的には、図４に示すように、反射電子像取得工程Ｓ２で得られた反射電子像を２値化処理し、ラーベス相を含む全ての析出物の面積と個数を求める。次に、ラーベス相のみを２値化し、ラーベス相の面積と個数を求め、全析出物の面積からラーベス相の面積を差し引いた値（ラーベス相以外の析出物の全面積）を全析出物の個数からラーベス相の個数を差し引いた値により除することで、ラーベス相以外の析出物１個当りの平均面積を求めることができる。
なお、ラーベス相以外の析出物としてはＭ２３Ｃ６、ＭＸ炭窒化物、Ｚ相化などが挙げられるが、これらの中でＭ２３Ｃ６は応力負荷による凝集・粗大化が促進されるため、Ｍ２３Ｃ６の１個当りの平均面積を求めることが望ましい。
(Average area calculation process)
The average area calculating step S4 is a step of obtaining an average area per precipitate other than the Laves phase, and as a method for obtaining the average area per precipitate other than the Laves phase, for example, the method shown in FIG. Can be used.
Specifically, as shown in FIG. 4, the reflected electron image obtained in the reflected electron image acquisition step S2 is binarized, and the areas and the number of all precipitates including Laves phases are obtained. Next, only the Laves phase was binarized, the area and the number of Laves phases were obtained, and the value obtained by subtracting the Laves phase area from the total precipitate area (total area of precipitates other than the Laves phase) By dividing by the value obtained by subtracting the number of Laves phases from the number, the average area per precipitate other than the Laves phase can be obtained.
Examples of precipitates other than the Laves phase include M23C6, MX carbonitride, and Z phase. Among these, M23C6 promotes agglomeration and coarsening due to stress load, and therefore per M23C6. It is desirable to obtain the average area of
（クリープ損傷度算出工程）
クリープ損傷度算出工程Ｓ５はラーベス相以外の析出物１個当りの平均面積を指標値とする耐熱鋼のクリープ損傷度Ｐｒを求める工程であって、例えば図５に示すラーソン・ミラー・パラメータ（ＬＭＰ）線図からクリープ損傷度Ｐｒを求めることができる。
（余寿命算出工程）
余寿命算出工程Ｓ６は耐熱鋼のクリープ損傷余寿命Ｔｆを求める工程であって、図５に示すクリープ損傷曲線Ｃ１がクリープ破断曲線Ｃ２と交わる点のＬＭＰをＰｃ、耐熱鋼の使用温度をＴ（℃）、使用時間をｔ（ｈ）とすると、下記に示す式（１）からクリープ損傷余寿命Ｔｆを求めることができる。
(Creep damage degree calculation process)
The creep damage degree calculation step S5 is a step for obtaining the creep damage degree Pr of the heat-resistant steel using the average area per precipitate other than the Laves phase as an index value. For example, the Larson Miller parameter (LMP) shown in FIG. ) Creep damage degree Pr can be obtained from the diagram.
(Remaining life calculation process)
The remaining life calculation step S6 is a step for obtaining the creep damage remaining life Tf of the heat-resistant steel. The LMP at the point where the creep damage curve C1 shown in FIG. 5 intersects the creep rupture curve C2 is Pc, and the operating temperature of the heat-resistant steel is T ( C) and the usage time is t (h), the creep damage remaining life Tf can be obtained from the following equation (1).
（余寿命率算出工程）
損傷率算出工程Ｓ７は耐熱鋼のクリープ損傷余寿命率φｃを求める工程であって、下記に示す式（２）からクリープ損傷余寿命率φｃを求めることができる。
φｃ＝ｔ／（ｔ＋Ｔｆ）・１００ ‥‥（２）
ただし、Ｔｆ：クリープ損傷余寿命、ｔ：耐熱鋼の使用時間（ｈ）である。
上記のように、耐熱鋼からなる機械部品の鋼組織に析出した析出物のレプリカを抽出レプリカ法により作成し、作成されたレプリカを走査型電子顕微鏡等の電子顕微鏡により撮像して析出物の反射電子像を得た後、得られた反射電子像の明度から析出物をラーベス相とラーベス相以外の析出物とに分類することで、機械部品の劣化を評価する際に応力依存性の低いラーベス相を除外することができる。
(Remaining life rate calculation process)
The damage rate calculation step S7 is a step of obtaining the creep damage remaining life rate φc of the heat-resistant steel, and the creep damage remaining life rate φc can be obtained from the following equation (2).
φc = t / (t + Tf) · 100 (2)
However, Tf: Creep damage remaining life, t: Use time (h) of heat-resistant steel.
As described above, a replica of precipitates deposited on the steel structure of mechanical parts made of heat-resistant steel is created by the extraction replica method, and the created replica is imaged with an electron microscope such as a scanning electron microscope to reflect the precipitates. After obtaining an electron image, Laves is less stress-dependent when evaluating deterioration of mechanical parts by classifying precipitates into Laves phases and precipitates other than Laves phases based on the brightness of the obtained reflected electron images. Phases can be excluded.
また、ラーベス相以外の析出物１個当りの平均面積を求め、該平均面積を指標値とする耐熱鋼のクリープ損傷度を求めることで、耐熱鋼のクリープ損傷評価曲線が図６に示すようなクリープ損傷評価曲線となり、応力が負荷される場合の劣化と応力が負荷されない場合の劣化とを区別して評価することが可能となる。
従って、機械部品の鋼組織に析出した析出物のレプリカを抽出レプリカ法により作成し、次いで上記レプリカを走査型電子顕微鏡等の電子顕微鏡により撮像して反射電子像を得た後、上記反射電子像の明度から析出物をラーベス相とラーベス相以外の析出物とに分類し、次いで上記ラーベス相以外の析出物１個当りの平均面積を求め、該平均面積を指標値とする耐熱鋼のクリープ損傷度を求めて機械部品の劣化を評価することで、使用条件が高温・高応力下であっても耐熱鋼からなる機械部品の劣化を正確に評価することができる。
Further, by obtaining the average area per precipitate other than the Laves phase and obtaining the creep damage degree of the heat resistant steel using the average area as an index value, the creep damage evaluation curve of the heat resistant steel is as shown in FIG. It becomes a creep damage evaluation curve, and it becomes possible to distinguish and evaluate deterioration when stress is applied and deterioration when stress is not applied.
Accordingly, a replica of the precipitate deposited on the steel structure of the machine part is created by the extraction replica method, and then the reflected electron image is obtained by imaging the replica with an electron microscope such as a scanning electron microscope, and then the reflected electron image. The precipitates are classified into Laves phases and precipitates other than Laves phases from the brightness of the steel, and then the average area per precipitate other than the Laves phase is obtained. Creep damage of heat-resistant steel using the average area as an index value By evaluating the degree of deterioration of the machine part, it is possible to accurately evaluate the deterioration of the machine part made of heat-resistant steel even if the use conditions are high temperature and high stress.
また、上述したように、電子顕微鏡の撮像視野が耐熱鋼の結晶粒界を含む視野となるように析出物のレプリカを電子顕微鏡により撮像して反射電子像を得ることで、析出物の凝集・粗大化が顕著となる視野で析出物のレプリカを電子顕微鏡により撮像することができ、これにより、使用条件が高温・高応力下であっても耐熱鋼からなる機械部品の劣化をより正確に評価することができる。
また、クリープ損傷度Ｐｒから耐熱鋼のクリープ損傷余寿命Ｔｆを求め、クリープ損傷余寿命Ｔｆから耐熱鋼のクリープ損傷余寿命率φｃを求めることで、耐熱鋼からなる機械部品の余寿命を正確に診断することができる。
In addition, as described above, a replica of the precipitate is imaged by an electron microscope so that the imaging field of view of the electron microscope becomes a field of view including the grain boundary of the heat-resistant steel, and a reflection electron image is obtained. A replica of precipitates can be imaged with an electron microscope in a field where coarsening becomes noticeable, and this allows more accurate evaluation of deterioration of mechanical parts made of heat-resistant steel even under high-temperature and high-stress conditions. can do.
In addition, the creep damage remaining life Tf of the heat resistant steel is obtained from the creep damage degree Pr, and the creep damage remaining life ratio φc of the heat resistant steel is obtained from the creep damage remaining life Tf. Can be diagnosed.
また、ラーベス相以外の析出物のうちＭ２３Ｃ６の１個当りの平均面積を求め、該平均面積を指標値とする耐熱鋼のクリープ損傷度を求めて機械部品の劣化を評価することで、Ｍ２３Ｃ６は応力依存性が高く、析出物の凝集・粗大化が応力によって促進されるため、使用条件が高温・高応力下であっても耐熱鋼からなる機械部品の劣化をより正確に評価することができる。 Further, by calculating the average area per M23C6 of precipitates other than the Laves phase, and determining the degree of creep damage of the heat-resistant steel using the average area as an index value, the deterioration of machine parts is evaluated. Stress dependence is high, and the aggregation and coarsening of precipitates are promoted by stress, so it is possible to more accurately evaluate the deterioration of mechanical parts made of heat-resistant steel even under high-temperature and high-stress conditions. .
１…機械部品
２…析出物
３…カーボンレプリカ膜
Ｓ１…レプリカ作成工程
Ｓ２…反射電子像取得工程
Ｓ３…析出物分類工程
Ｓ４…平均面積算出工程
Ｓ５…クリープ損傷度算出工程
Ｓ６…余寿命算出工程
Ｓ７…余寿命率算出工程
DESCRIPTION OF
Claims (3)
前記機械部品の鋼組織に析出した析出物のレプリカを抽出レプリカ法により作成し、
次いで前記レプリカを電子顕微鏡により撮像して前記析出物の反射電子像を得た後、
得られた反射電子像の明度から前記析出物をラーベス相とラーベス相以外の析出物とに分類し、
次いで前記ラーベス相以外の析出物１個当りの平均面積を求め、
該平均面積を指標値とする耐熱鋼のクリープ損傷度をラーソン・ミラー・パラメータ（ＬＭＰ）線図から求め、
前記クリープ損傷度をＰｒ、前記ラーソン・ミラー・パラメータ（ＬＭＰ）線図においてクリープ損傷曲線Ｃ１がクリープ破断曲線Ｃ２と交わる点のラーソン・ミラー・パラメータ（ＬＭＰ）をＰｃ、耐熱鋼の使用温度をＴ（℃）、使用時間をｔ（ｈ）として、クリープ損傷寿命Ｔｆを
Ｔｆ＝（10 ((Pc-Pr)・100/T) -1）ｔ
で求めて前記機械部品の劣化を評価することを特徴とする機械部品の劣化
評価方法。 A method for evaluating the deterioration of mechanical parts made of heat-resistant steel,
Create a replica of the precipitate deposited in the steel structure of the machine part by the extraction replica method,
Next, the replica was imaged with an electron microscope to obtain a reflected electron image of the precipitate,
The precipitates are classified into Laves phase and precipitates other than Laves phase from the brightness of the obtained reflected electron image,
Next, the average area per precipitate other than the Laves phase is determined,
The creep damage degree of heat-resistant steel using the average area as an index value is determined from a Larson-Miller parameter (LMP) diagram ,
The creep damage degree is Pr, the Larson Miller parameter (LMP) at the point where the creep damage curve C1 intersects the creep rupture curve C2 in the Larson Miller parameter (LMP) diagram, and the operating temperature of the heat resistant steel is T. (° C.), the usage time is t (h), and the creep damage life Tf is
Tf = (10 ((Pc-Pr) · 100 / T) −1) t
Deterioration evaluation method of mechanical parts, characterized in that in determined to evaluate the degradation of the mechanical parts.
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