Superaustenitic Fe-20Cr-18Ni-6Mo-0.2N (UNS S31254 ) and Superferritic Fe-29Cr-4Mo ( UNS S44700 ) stainless steels have been successfully cladded on mild steel substrates by laser beam with a pneumatic powder feed system. The above surface alloys consist of fine cellular dendrites of austentic structure in the first case and of ferritic structure in the latter case with slight segregation of alloying elements mainly Cr and Mo in the dendrite boundaries in both cases. However the dendrite boundaries in the superaustenitic stainless steel surface layer (∼2μm) are much thicker than those in superferritic stainless steel surface layer (∼0 .5μm).

Localised corrosion performance of the surface alloys obtained by laser surface cladding ( LSC ) and their commercial counterparts were studied by potentiodynamic anodic polarisation in 0.5M NaCl and 1M FeCl3 solutions and by long term immersion tests in 1M FeCl3 ( acidified to pH 0.4 ). Both LSC surface alloys and commercial counterparts display excellent passive behavior and do not suffer pitting corrosion in the anodic polarisation tests .After immersion for two months in 1M FeCl3 ( acidified to pH 0.4 ), only slight pitting corrosion was observed in both types

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1995
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