Effect of inadequate heat treatment on creep strength of 12Cr–Mo–V steel

Abstract

Solution treatment of 12Cr–Mo–V steels below the specified temperature range leads to the development of spheroidized microstructures with dramatically reduced creep resistance. This is known to have resulted in the premature service failures of superheater tubing. Compositional and mechanical property checks currently specified in the relevant standards may not be sufficient to reveal deficiencies. Steels with Cr–Ni equivalents at the uppermost extreme of the range possible within the compositional limits of the tube steel standards show enhanced susceptibility to both δ– and α–ferrite formation. The significance of this is discussed in relation to creep strength, with particular reference to the differences between the effects of α- and δ-ferrite.

MST/147