INVESTIGATION OF THE MICROSTRUCTURES OF IRON-BASED WROUGHT CR-NI-MO DUPLEX ALLOY

Samples of duplex stainless steel, consisting of iron-based Cr-Ni-Mo a hoy containing some other elements undergoing various heat treatments after having been wrought at 1150 degrees C, have been investigated us ing X-ray diffraction, thermal analysis and metallographic techniques. It is determined that some intermetallic phases such as Laves, mu, G, mu, R, chi, and some carbide phases as such M23C6, M7C3, M6C may be f ound in these samples and that the ratio of carbide phases decreased i n samples annealed at 950 degrees C. In samples cooled in liquid nitro gen, it is seen that some dissolving elements in the matrix have accum ulated around the sigma phases and some precipitation phases have occu rred. It is concluded that the use of annealing of this material at 95 0 degrees C affects the chemical, mechanical and other properties adve rsely. (C) 1997 Elsevier Science S.A.