Corrosion Behaviour of Sintered Duplex Stainless Steel

摘要

Duplex stainless steels were produced by mixing AISI type 316L and AISI type 434L powders, using different powders percentages (three different initial ferrite/austenite ratios were selected: 75/25; 50/50 and 25/75). Some post-sintering thermal treatments in argon atmosphere were also carried out in order to dissolve sigma phase. The corrosion behaviour of duplex stainless steels was found to depend much more on residual porosity than on the phase constitution of the materials. The increase in the ferritic powder results in a lower open porosity and, in turn, in a better corrosion resistance. Inert atmosphere heat treatment carried out to dissolve sigma phase causes an uncontrolled oxidation, which tends to worse the corrosion resistance. Solution annealing of these materials should then be carried out in a reducing atmosphere.