POSTTREATMENT OF TITANIUM NITRIDE BY ION-IMPLANTATION

The properties of titanium nitride and the effects of a post-treatment by ion implantation on coatings made of it are first considered in te rms of data available from the scientific literature; 70 references ar e cited. Data obtained in the present work are then combined with thes e to offer an explanation of the process mechanisms and structural eff ects involved. The present work covers monolithic TiN coatings, deposi ted onto cemented carbide by chemical vapor deposition or steel by phy sical vapor deposition, and implanted with gas or metal ions at differ ent doses and acceleration energies. Tile results considered together confirm that large changes in the residual stress and the strain distr ibutions are introduced into the implanted zone (IZ) and extend well b eyond forming an implantation affected zone (IAZ) which extends to a d epth of several microns The surface of the IZ is amorphized softened b y non-metallic implants but not by metallic ions which increase the ha rdness. The residual stress in the IZ is high, tensile or compressive depending on whether vacancy generation and atom peening effects domin ate and is accompanied by concomitant high, irregular, distributions o f strain caused by a high dislocation density and/or grain comminution and include high fractions of lattice vacancies. The forward momentum of the ions introduces a dense dislocation network and high residual stress in the IAZ corresponding to the so-called lo ng ran ge effect. The dislocation density increases and the residual stress becomes more compressive with increasing ion momentum. (C) 1998 Elsevier Science L td.