Friction-induced microstructural variations in steels subjected to low-energy elevated-temperature nitrogen ion implantation

The effects of friction and low-energy elevated-temperature nitrogen ion implantation on surface-layer microstructure are investigated. X-ray diffraction, optical and electron microscopy were used to analyze microstructural variations in the surface layers of several martensitic-ageing and stainless steel. Nitrogen implantation produces solid solutions and precipitates new phases in surface layers that are several micrometers thick. Tribological measurements made on steel blocks in a block-on-plane tester show that the implantation increases the wear resistance. Both ion implantation and subsequent wearing influenced microstructure and mechanical properties of the surface layer. Thermal spikes, plastic deformation and elastic energy stored in the surface layer of ion-implanted steels determine the nature of microstructure transformations. (C) 1999 Elsevier Science S.A. All rights reserved.