Steel Surface Roughening by Transient Self Dewetting After Pulsed Electron Beam Melting

Abstract

Experimental evidence of surface roughening by transient self dewetting of metallic surfaces is presented. Steel surfaces are melted by a pulsed electron gun and the subsequent fast cooling against the substrate gives rise to the formation of characteristic patterns that are attributed to the dewetting of the liquid film. The patterns formed are similar to those obtained by spinodal dewetting, that is, when the dewetting action develops from a non-linear instability on the liquid surface, and not from hole nucleation. The patterns are characterised by the presence of valleys of unmelted substrate surrounded by ridges of resolidified material. Martensitic steels can form ferritic substrates with martensitic ridges. Two possible mechanisms respon sible for the onset of the surface instability are proposed.