AbstractOne possibility for surface treatment using lasers is to cause significant changes in surface composition and microstructure. However, techniques for changing composition remain poorly developed and the mechanisms controlling final microstructure are still not fully understood. A very simple technique for supplying alloying additions has been used in the present work to modify a ferritic stainless steel and has been shown to be capable of causing large changes in composition. As-alloyed layers remain fairly inhomogeneous and a second melting is necessary, at which time treatment conditions can be selected to obtain the required microstructural state. There is a relationship between the formation of the microcrystalline layers observed and the cooling rate and the formation of the microcrystalline layers can be analysed in terms of continuous crystal nucleation. As expected, the abrasive wear resistance of the surface layers improved as a result of the increase in hardness.MST/909