Investigation into the transformation products of CD3MN cast duplex stainless steel
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The transformation products for CD3MN cast duplex stainless steel (DSS) were investigated between the temperatures of 600 to 9500C. The primary research evaluated the kinetics of sigma ([Sigma]) phase formation by developing the time-temperature-transformation diagram for CD3MN and comparing these results to wrought duplex stainless steel transformation diagrams. The results of the study showed that the nose of the time-temperature-transformation diagram is dependent on chemistry and not a difference between the cast and wrought structures. The investigation found that sigma formed in the CD3MN alloy between the temperatures of 700 and 9000C, with the fastest rate of formation occurring at 8000C. By modeling the sigma growth by the diffusion of Cr and Mo through the matrix, it was found that the growth of sigma is very slow at temperatures below 9000C and the phase percent sigma is dependent on the accelerated diffusion of Cr and Mo at the grain boundaries and nucleation of new sigma.