Investigation of the Nitrided Layers in Ductile Iron

Abstract

The ductile cast iron has been presenting an accentuates growth of production due to lo its interesting mechanical properties and economic advantages of production, in comparisón to the steel or other ferrous alloys. In this wórk, samples of three compositions of this material in lite as-melted state and samples austenitized al 900°C and austempered for 320°C in melted salts, were plasma nitrided for 5 hours ai 500 °C using continuous current and atmosphere constituted of the 80% H₂ - 20% gaseous moíslure. The austempered samples present the highest hardness values of nitrided layers and the best resistance to wear. In the case of pearlitic matrix, the nitrogen diffusion and the formation of the consequent nitride will happen in the ferrite lamellas. Such difusión will be associated with the position of those lamellas in relation to the surface, where the nitrogen atoms come from.