Abstract:

The precipitates in 20Cr11MoVNbNB heat resisting steel quenched at 1130℃ and tempered at 700℃ for 4h, and subsequently creeped at 550℃ for 5462h and 650℃ for 2968h were studied by means of XRD, TEM, etc . It is shown that M 23 C 6 and MC are main precipitates in 20Cr11MoVNbNB steel. The coarsening kinetics of M 23 C 6 and MC have the same 4th power law, synthetically controlled by both block diffusion and dislocation diffusion, and regardless of their original precipitating positions. The coarsening rate of M 23 C 6 is faster than that of MC.

Key words: 20Cr 11MoVNbNB heat r esist ing steel, cr eep, pr ecipitat es