Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Effect of Nitriding on Fatigue Crack Initiation and Growth Rate in Ni-Cr-Mo Steel

SNCM강의 피로균열의 발생 및 전파속도에 미치는 질화처리의 영향

  • Kim, Min-Gun (Dept. of Mechanical Engineering, Kangwon National University) ;
  • Lim, Bok-Kyu (Dept. of Mechanical Engineering, Kangwon National University)
  • 김민건 (강원대학교 공과대학 기계메카트로닉스공학부) ;
  • 임복규 (강원대학교 공과대학 기계메카트로닉스공학부)
  • Received : 2003.09.01
  • Published : 2003.11.30
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Abstract

Effect of nitriding on fatigue crack initiation and growth rate has been studied in Ni-Cr-Mo steel. Specimens were nitrided at $860^{\circ}C$ for 15 hr. The fatigue limit of nitrided specimens were superior to those ofannea1ed($860^{\circ}C$, 15 hr) specimens. Based on detailed observations of slip band and micro crack initiation, it is concluded that the excellent fatigue limit of nitrided specimens is attributed to improved slip initiation resistance by nitriding. The characteristic of fatigue crack growth rate of nitrided specimens was investigated by comparing with those of annealed specimens. It was found that the crack growth rate was markedly decreased and the threshold stress intensity factor range was improved by nitriding. It is concluded that the excellent fatigue limit of nitrided specimens is also attributed to improved fatigue crack growth rate and threshold stress intensity factor range by nitriding.

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