Creep Damage of 1Cr--1Mo--0.25V Steel

Microstructural changes and degradation of high temp. tensile properties due to creep damage have been studied on 1Cr--1Mo--1/4V steel specimens obtained by interrupting the creep test up to 9000 h at 600 deg C. The loss of strength in the 1Cr--1Mo--1/4V steel after long term creep exposure is due to three mechanisms: (1) the strength loss accompanying the change in the caribde morphology that usually occurs during tempering, (2) the strength loss resulting from local recovery of ferrite matrix in the vicinity of prior austenite grain boundary carbide particles, and (3) the strength loss due to formation of voids and cracks. It is considered that the progress of creep damage during primary creep stage is attributed mainly to the first mechanism, and that of tertiary creep to the second one which is most important. On the other hand, since no cracks and a limited number of voids were observed at the grain boundary, it is assumed that the third one it not essentially responsible for creep damage of the Cr--Mo--V steel studied. 16 ref.--AA