抄録
Low cycle fatigue tests of cobalt-base superalloy HA-188 were conducted at 700°C in the strain rate range of 3.6×10-5 to 2.0×10-2 sec-1. Experimental results were compared with estimated results in consideration of fracture mode. The initiation and the propagation of the main crack was observed during fatigue test by using the surface replica method. The results obtained in this study are summarized as follows.
(1) Fatigue life decreased with decreasing strain rate, and the slope of log Δεp-log Nf were-0.66 at any strain rate.
(2) In the universal slope method, experimental results were distributed between average band and lowerband, and fallen within a factor of two of the results estimated by an equation based on the Ohtani-Nakamura's equation.
(3) Relation between experimental results and estimated results was not affected by fracture mode in the universal slope method, but affected in equation based on the Ohtani-Nakamura's equation.
(4) The ratios of Ni/Nf (Ni: crack initiation life) were decreased as the strain rate and the strain range decreased.
