1997 Volume 37 Issue 2 Pages 161-168
A microalloyed steel was precoated with three different thicknesses of Ni-Cr-W-Mo-Cu-C-B powder and laser-surface-alloyed in order to achieve a corrosion-resistant surface alloy. In general, laser treated alloys showed good adherence and considerable penetration into the base material, which varied with laser treatment conditions and initial coating thicknesses. Under conditions studied, laser treated alloys presented a dendritic structure. The degree of dilution increased as both laser scanning rate and initial coating thickness decreased. The lowest iron content at the surface was reached for samples with a 1 000 μm initial coating thickness and laser treated at the maximum scanning rate 0.054 ms-1. This low iron content jointed to a high content of chromium and nickel on the surface gave rise to the formation of a protective and stable passive layer that implied a high corrosion resistance in Na2SO4 0.1 M. The samples with 250 and 500 μm coating thicknesses presented in most cases a martensitic transformation within the coating due to the high degree of dilution between coating and base material decreasing drastically the corrosion resistance of the melted coating.