THE EFFECT OF LASER-SURFACE MODIFICATION ON THE CORROSION BEHAVIOR OFFE AND AL BASE ALLOYS

The effect of laser surface modification on the corrosion behaviour of Fe-10Cr-13P-7C and Al-Si base alloys was studied. Using the laser pow der injection technique an amorphous surface layer with a composition Fe-10Cr-13P-7C could not be obtained, although this alloy is amorphous after melt-spinning. Formation of crystalline phases in the system Fe -Cr-P-C led to a high compositional heterogeneity due to the low solub ility of phosphorus and carbon in the iron matrix. This resulted in a low corrosion resistance and a selective dissolution of phases with a low chromium and phosphorus content. The pitting corrosion resistance of aluminium alloys could be significantly improved by laser surface r emelting. The positive effect of the laser remelting became less signi ficant for alloys containing high amounts of silicon and not observed in the presence of primary silicon particles. A common feature for bot h material groups was the non-uniform attack on the laser-treated samp les. Especially typical was the selective dissolution of the interface regions of the neighboring laser traces. The results showed clearly t hat the formation of a homogeneous structure comprising both the centr al part of the laser traces and the interfacial regions would be requi red in order to achieve laser-treated surface layers with a high corro sion resistance.