The environmental behaviour of SAE 304L stainless steel sintered in the presence of a copper base additive

The effect of a copper-based alloy admixed to stainless steel powders as a transient liquid phase forming additive on the corrosion resistance of a sintered stainless steel in IN H₂SO₄ has been investigated. It was found that the quantity of the additive, its particle size distribution as well as the sintering cycle have a substantial influence on the surface morphology and the corrosion resistance of the sintered specimens. The residual porosity in the sintered specimens was substantially reduced in different samples compacted from the same powder mixtures by employing two different sintering cycles having the same sintering temperature. A final residual porosity of 6.5% containing small (<5 μm), round and isolated pores was observed in samples compacted from fine particle size (-44 μm) SAE 304L powder containing 7 wt.% fine (-44μm) particle additive. A substantial improvement in the environmental behaviour of specimens containing 3 wt.% additive was recorded during open circuit potential measurements and potentiodynamic tests. An enrichment of the surface by copper after exposure to the IN H₂SO₄ environment due to selective dissolution of the sample by the electrolyte was detected by AES analysis, most probably acting synergestically with the improvement in the surface residual open porosity thus improving the environmental behaviour of the specimens.