Laser surface alloying of AISI 304-stainless steel with molybdenum for improvement in pitting and erosion-corrosion resistance

The present study concerns laser surface alloying (LSA) of AISI 304 stainle ss steel (304-SS) with predeposited Mo (by plasma spraying) to enhance pitt ing and erosion-corrosion resistance of the substrate. A parametric correla tion between the alloyed zone (AZ) depth (w) vis-a-vis incident laser power density (Q) and linear scanning speed (upsilon) indicates that w is direct ly related to Q but varies inversely with upsilon. Both microstructure and chemistry of the AZ are strong functions of the LSA parameters. LSA seems t o improve the microhardness level in the AZ by 2-3 rimes that of the substr ate. The optimum LSA conditions in terms of predeposit thickness, Q and ups ilon have been identified to achieve the desired microstructure, compositio n and mechanical properties. LSA under such optimum conditions significantl y improves the pitting corrosion resistance in terms of critical potential for pit formation (E-PP1) and pit growth (E-PP2). In addition, the erosion- corrosion resistance in 20 wt.% sand in 3.56 wt.% NaCl solution registers a marked improvement. Thus, it is concluded that LSA of 304-SS with Mo is an appropriate technique to enhance the resistance to pitting and erosion-cor rosion ill stainless steel. (C) 1999 Elsevier Science S.A. All rights reser ved.