2004 Volume 53 Issue 9 Pages 446-450
ID blade of meta-stable austenitic stainless steel shows an elastic anisotropy and potential susceptibility to delayed fracture due to the strain-induced martensite. Authors first estimated the five elastic stiffness coefficients of the ID blade from the orientation dependency of the laser-excited Lamb waves. Rayleigh wave velocity decreased with a maximum difference of 400m/s with angles from the rolling direction, while the sheet velocity varied with a maximum increase of 500m/s. Hydrogen pre-charged ID blade showed the wave velocities higher than that of the as-received one. Fracture strength of hydrogen pre-charged ID blade decreased to 43% and 73% of those of the as-received one in the rolling and transverse direction, respectively. The blade suffered brittle fracture after 4.17ks hydrogen charging at the radial fastening stress level. Both the acoustic emission source location and fractographic observation suggested the delayed fracture assisted by the strain-induced martensite.
