FE-CR-NI-MO-C ALLOYS PRODUCED BY LASER-SURFACE ALLOYING

Several Fe-Cr-Ni-Mo-C alloys were produced by laser alloying on plain carbon steel substrates, using the blown powder technique. It was foun d that a careful selection of the laser treatment parameters results i n alloyed layers free of defects and with a homogeneous chemical compo sition. The structures were martensitic, fully austenitic and austenit ic-ferritic, depending on the chemical composition. The high cooling r ates were found to affect the austenitic-ferritic structures, which sh owed a larger quantity of delta ferrite than that predicted by the Sha effler diagram. Surface alloys produced by laser processing, with chem ical composition similar to that of conventional austenitic stainless steels, showed better pitting corrosion resistance than their bulk cou nterparts produced by conventional techniques, despite their higher ca rbon content.