タービンロータ鋼の過熱蒸気環境下の疲労き裂の発生と伝ぱ

概要

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The fatigue crack initiation and the crack growth rate of chromium-molybdenum-vanadium steel in super heated steam were studied by the fracture mechanics approach in respect with the cyclic frequency and oxygen concentration in the surrounding atmosphere. Fatigue tests were conducted at 839 K at cyclic frequencies of 600, 10, 1 and 0.1 cpm. In order to examine the influence of environment upon the fatigue behaviors, the high temperature air and argon gas were also employed as the surrounding atmosphere. It was found that the number of cycles to crack initiation decreased remarkably and the crack growth rate increased with decreasing cyclic frequency and with increasing oxygen concentration. As for the influence of metallurgical factors upon fatigue behaviours, it was found that the number of cycles to crack initiation was remarkably reduced by the existence of inclusions such as manganese sulfide. The influence of environment upon the fatigue crack growth rate was examined under consideration of the fatigue crack growth rate per unit time.
1982-07-15