Creep crack growth characterization of Type 316 stainless steel using miniature specimens

Remaining life estimation of components which experience elevated-temperature service requires knowledge of creep-crack-growth characteristics of the service-exposed material. In most cases only a small amount of material from in-service components is available for testing; thus, there is a need to design and benchmark test methods that use miniature creep-crack-growth specimens. In order to address this problem, a creep-crack-growth test methodology was developed using miniature single edge-notched tension specimens. The material used in this work was from a well characterized heat of Type 316 stainless steel, for which creep-crack growth data were previously obtained using conventional compact-tension type and center-cracked-tension type specimens. Good correlation was obtained between the crack growth rate and Cj, where Cj is the experimental counterpart of C*. The details of the analytic procedure for miniature specimens, particularly for small crack lengths, are presented. The current results agreed very well with those for large specimens as well as with creep-crack growth data obtained by other investigators.