EFFECT OF ZIGZAG GRAIN BOUNDARY ON CREEP RUPTURE OF A 10Cr-15Co-Ni-BASE WROUGHT SUPERALLOY

Investigation was made of the effect of the zigzag or straight grain boundary, which may be obtained by two different schemes of heat treatment, on the creep rupture of a 10Cr-15Co-Ni-base wrought superalloy, especially, on the reason whyits strength and plasticity at elevated temperature can be improved by the zigzaggrain boundary. It is shown that the zigzag grain boundary may delay the initiation, growth and propagation of crack, as well as may also influence the crack morphology and the fracture mode markedly. Furthermore, the zigzag grain boundary may intensively inhibit the grain boundary sliding and retard the crack joining, thus, force the bulk-grains to take part in more deformation. It displays an important role in the tertiary stage of creep. The creep life to failure of the alloy tested with zigzag grain boundary was increased by a factor of 1/4, and the plasticity was also improved slightly.