Creep Properties of Intercritical Heat Treated Boron Added Modified 9Cr-1Mo Steel

Creep properties of intercritically heat-treated (ICHT) boron free modified 9Cr-1Mo steel (P91-IC) and boron containing modified 9Cr-1Mo (P91B-IC) steel have been studied at 923 K over a stress range of 50-120 MPa. Minimum creep rate of the P91B-IC steel was significantly lower than the P91-IC steel. Stress exponent and threshold stress values in P91-IC and P91B-IC steels were found to be 6.5 and 28 MPa, and 8.7 and 38 MPa respectively. P91B-IC steel has exhibited higher creep rupture life than the P91-IC steel. Higher creep rupture strength in the P91B-IC steel as compared to P91-IC steel has been attributed to the presence of stable M23C6 precipitates at the lath boundaries and other high angle boundaries. The creep rupture strengths of both the ICHT steels were lower than the respective base metal. Graphic

Automated summary

The boron containing modified 9Cr-1Mo steel (P91B-IC) exhibited higher creep rupture strength and lower minimum creep rate compared to the boron free modified 9Cr-1Mo steel (P91-IC) after intercritically heat-treated at 923K.