報告書番号

285055

タイトル（和文）

インコネル６００合金の応力腐食割れに及ぼす水質因子の影響評価

タイトル（英文）

THE EFFECT OF ENVIRONMENTAL FACTORS ON THE SCC OF INCONEL ALLOY 600 IN DEAERATED HIGH TEMPERATURE WATER

概要 （図表や脚注は「報告書全文」に掲載しております）

本報告は，インコネル６００合金のＳＣＣに及ぼす水質因子の影響を調べることを目的とし，３５０℃高温脱気試験す水溶液中におけるＳＣＣ試験，電位－ｐＨずならびに同合金の粒界特性の詳細な検討を行うことにより，粒界特性－水質因子－ＳＣＣ感受性について考察したものである。主要な結果は以下の通りである。（１）．インコネル６００合金のＳＣＣ感受性は，酸性水溶液中ではクロム欠乏層の成長と共に高くなる。中性水溶液中（微酸性～微アルカリ性）では，同合金のＳＣＣ感受性はいずれの熱処理剤とも低い。荷性アルカリ環境では，粒界炭化物が成長し粗大化するに伴いＳＣＣ感受性は低くなる。（２）硼酸はアルカリ側のＳＣＣを抑制するが，酸性側ではＳＣＣ抑制効果は認められなかった。

概要 （英文）

THE EFFECT OF ENVIRONMENTAL FACTORS ON THE INTERGRANULAR STRESS CORROSION CRACKING (SCC) OF INCONEL ALLOY 600 HAS BEEN STUDIED IN DEAERATED WATER AT 350 DEGREES C BY USING THE CONSTANT EXTENSION RATE TEST (CERT) AND U-BEND SCC TEST METHODS. SCC WAS ACCELERATED METHOD IN DEAERATED WATER CONTAINING 10 PPM HCL. THE SCC SUSCEPTIBILITY OF SENSITIZED ALLOY 600 WAS HIGHER THAN THOSE OF ANNEALED AND DESENSITIZED ALLOY 600. THE SCC SUSCEPTIBILITY OF INCONEL ALLOY 600 WAS LOWIN DEAERATED WATERS CONTAINING H3BO3 AND NH4OH. ON THE OTHER HAND, SCCWAS PROMOTED IN DEAERATED WATER CONTAINING NAOH. IN THIS CASE, THE SCCSUSCEPTIBILITY OF ALLOY 600 WAS IN THE FOLLOWING ORDER : MILL ANNEALEDALLOY 600, SENSITIZED ALLOY 600, DESENSITIZED ALLOY 600. THE ADDITION OF BORIC ACID TO AN NAOH SOLUTION SUPPRESSED THE SCC, BUT ITS ADDITION TO HCL SOLUTION WAS NOT SUPPRESIVE. THE POTENTIAL-PH DIAGRAM FOR THE CR-H20 SYSTEMS AT 350 DEGREES C IN DICATED THAT THE SURFACE FILM OF INCONEL ALLOY 600 WAS STABLE IN WATER CONTAINING H3BO3 OR NH4OH. ON THE OTHER HAND,NI AND CR, THE MAIN COMPOSITIONS OF ALLOY 600, WERE UNSTABLE IN HCL AND NAOH SOLUTIONS, RESPECTIVELY. THEREFORE, THE SCC SUSCEPTIBILITYOF ALLOY 600 WAS LOW IN H3BO3 AND NH4OH SOLUTIONS, BUT ITS SUSCEPTIBILITY WAS HIGH IN HCL AND NAOH SOLUTIONS. THE RELATIONSHIP BETWEEN GRAIN BOUNDARY CHARACTERISTICS AND ENVIRONMENTAL FACTORS AND SCC SUSCEPTIBILITY IS DISCUSSED.

報告者

キーワード