A FRACTURE MECHANICS AND FRACTOGRAPHIC STUDY OF FATIGUE CRACK PROPAGATION RESISTANCE IN 17-4 PH STAINLESS STEELS

A determination of fatigue-crack propagation resistance in heat-treated samples of 17-4 PH stainless steel has been made, together with correlative microscopic observations via electron fractography. Two rolled plates of 1/2-in. thickness were investigated, one vacuum melted (VM) and heat treated to the H1050 condition and the other argon oxygen melted (AOM) and heat treated to the H1050 and H1150 conditions. Crack-growth rates (da/dN) were obtained in ambient laboratory air as a function of stress-intensity factor range delta K using single-edge-notched (SEN) tension specimens. The effect of stress ratio R on da/dN was examined; values of R = 0.04, 0.40, 0.67, and 0.80 were employed. Microscopic modes of crack propagation determined by electron fractography were utilized to explain differences in macroscopic crack-growth behavior. Both cleavage and microvoid coalescence can appear as modes of cyclic crack propagation in this family of steels, to the detriment of cyclic crack-growth resistance. When cleavage is present, the amount appears to be independent of delta K over a wide spectrum of delta K levels. Moreover, the incidence of cleavage (and accelerated cyclic crack propagation rates) increases significantly with ratio R. It was found that the heat treatment can be adjusted to minimize the incidence of cleavage, and that slight variation in alloy processing serves to eliminate cleavage and promote striation formation, while enhancing the fracture toughness. /Author/

  • Corporate Authors:

    Naval Research Laboratory

    4555 Overlook Avenue, SW
    Washington, DC  USA  20375-5320
  • Authors:
    • Crooker, T W
    • Hasson, D F
    • Yoder, G R
  • Publication Date: 1975-5-21

Media Info

  • Pagination: 22 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00127756
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: NRL-7910 Final Rpt.
  • Files: TRIS
  • Created Date: Dec 16 1975 12:00AM