SEVERAL points made in the above paper deserve some clarification. First, it is stated (bottom of p. 473) that a partial decrease in carbon content in the HAZ occurred due to the change in density accompanying the fcc ~ bet transformation. This does not seem to be at all consistent with the laws of conservation of matter. Perhaps the authors might detail the expected accuracy of the microbrobe analysis, the experimental aspects of which are not detailed. Secondly, the axes of Figs 8-12 are labelled as log AK and log da/dN, respectively and then values such as l0 TM marked on the axes. These axes should probably simply be labelled as AK, etc. instead of log AK. Most important, it is stated (starting from second line on p. 474) that the FCGRs are highest in the weldment (assumed to mean WM). Yet looking at Fig. for example, the lowest FCG rate is in the base metal in the range AK = 8 MPa m ~/2 to 20 MPa m t/2. The authors further state that the threshold is highest in the weldment (weld metal?), yet from Fig. , the thresholds of Bl, B2 and B3 specimens are virtually coincident. Furthermore, from Figs 9 and 10, the BM, not the WM, seems to have the highest threshold.
On p. 475 (9th line from the top), the authors state that the higher FCG rate in the HAZ is due to residual stress. Two points need clarification:
(1) Residual stresses are present in both the WM and HAZ and are usually higher in the WM . For this reason, residual stress cannot explain the difference in FCG rates of the two zones unless the actual values of the residual stresses are determined.
(2) Residual stresses in C(T) specimens are usually compressive [4-6] at the notch/crack tip. The effect of residual stress would then be to decrease the FCG rate. This indeed has been documented many times [I-7]. Residual stress cannot therefore be used to explain the higher rate of FCG in the HAZ.
Perhaps the authors could comment on these points.