LASER-SURFACE TREATMENTS TO IMPROVE THE INTERGRANULAR CORROSION-RESISTANCE OF 18 13/NB AND 304L IN NITRIC-ACID/

Surface melting of 18/13/Nb austenitic stainless steel, using a 2 kW c ontinuous wave CO2 laser is shown to improve the resistance of the mat erial to the propagation of localised, ''intergranular, corrosion (end grain attack). The same technique can be used to eliminate sensitised material in the surface layers of 304L plate either preventing the in itiation of intergranular corrosion or halting corrosion which has alr eady started. Alloying of the 304L surface by injecting extra chromium or cladding with grade 310 steel appears to provide little extra bene fit, compared to simple surface melting. However, this is probably due to the incomplete coverage of the samples tested since the clad and a lloyed surfaces show very little evidence of corrosion,