1979 Volume 65 Issue 7 Pages 932-938
For the failure analysis or in-service inspection of high tempemature parts of power plants, the estimation of the creep life remaining after a given service period and evaluation of such estimates are very important, especially when the parts have been accidentally overheated.
It the cases, the life fraction rule is offer applied. To lay a foundation for this practice, creep rupture tests and metallographic studies were conducted on type 18-8-Mo stainless steel that had been used as superheater tube at 590-615°C for 27000 hours. It was found that a serive temperature with ±15°C, one of the indispensable conditions for reliable estimation of the remaining creep life is difficult to determine by means of metallographic observations and that for the estimation of remaining life by a comparison between the used tube and unused tube in creep rupture testing, both tubes must be heated equally. As a result, the estimation based on creep strain (tangential strain on outside periphery of the tube) was found to be the best method capable of non-destructive testing for a secular change of remaining life.