Abstract :
Dual-phase ferritic–martensitic 3CR12 steel, exhibiting an excellent corrosion resistance under ambient conditions, is a
potential substitute for FeCrNi stainless steels in many applications. However, the steel suffers pitting corrosion in Cl -
containing environments, usually associated with the presence of non-metallic inclusions. The present work investigates the
possibility of improvement of the pitting corrosion performance of hot-rolled and annealed 3CR12 steel using a laser surface
melting (LSM) technique. The laser processing was carried out using a 3 kW CW Nd:YAG laser with 10 and 13 mm line beam
profiles. Pitting resistance in de-aerated 3.5% NaCl solution was substantially increased by LSM. The degree of improvement is
associated with the formation of ferrite and reduction of martensite in the melt region, the extent of which depends on the
processing parameters. Observation of pitting morphologies of the laser-melted surfaces showed that corrosion was initiated at
the ferrite grain boundaries, where the martensite or possibly impurities were located, compared with more random pitting in the
banded microstructure of the initial steel.
