Abstract
Precipitation processes have been quantitatively studied in a series of austenitic stainless steels (17Cr–12.5Ni) to which different stabilizing additions (e.g. V,Ti,Nb) were made. The atomic proportions of the stabilizing elements and the interstitials (C and N) were kept constant. It was found that when two stabilizing elements were added, both of these were present in the MX precipitates. Substantial amounts of Cr dissolved in the MX precipitates. This effect was greater for nitrides (which were all V rich) than for carbides and led to a higher solubility for the nitrides which consequently coarsened faster during high-temperature aging. The coarsening behaviours of TiC and NbC were complicated by the fact that TiC partially transformed to M23C6 at long aging times while, in the Nb-stabilized alloy, M23C6 transformed to NbC. It is concluded that Nb is a considerably more effective stabilizing addition than Ti.
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