THE ENVIRONMENTAL BEHAVIOR OF SAE 304L STAINLESS-STEEL SINTERED IN THE PRESENCE OF A COPPER-BASE ADDITIVE

The effect of a copper-based alloy admired to stainless steel powders as a transient liquid phase forming additive on the corrosion resistan ce of a sintered stainless steel in 1N H2SO4 has been investigated. It was found that the quantity of the additive, its particle size distri bution as well as the sintering cycle have a substantial influence on the surface morphology and the corrosion resistance of the sintered sp ecimens. The residual porosity in the sintered specimens was substanti ally reduced in different samples compacted from the same powder mixtu res by employing two different sintering cycles having the same sinter ing temperature. A final residual porosity of 6.5% containing small (< 5 mu m), round and isolated pores was observed in samples compacted f rom fine particle size (- 44 mu m) SAE 304L powder containing 7 wt.% f ine (- 44 mu m) particle additive. A substantial improvement in the en vironmental behaviour of specimens containing 3 wt.% additive was reco rded during open circuit potential measurements and potentiodynamic te sts. An enrichment of the surface by copper after exposure to the 1N H 2SO4 environment due to selective dissolution of the sample by the ele ctrolyte was detected by AES analysis, most probably acting synergesti cally with the improvement in the surface residual open porosity thus improving the environmental behaviour of the specimens. (C) 1997 Elsev ier Science S.A.