Damage zone produced by the bombardment of stainless steel using Ti nitride PVD coatings

This paper presents the damage zone and defects produced by TiN thin film deposition on stainless steel using DC magnetron sputtering to produce collisions between the TiN ions and the substrate. The PVD process used a low operative pressure, reducing the bombardment damage on the substrate, in comparison with other methods. Internal friction (IF) and elastic modulus measurements were carried out in TiN-PVD coated AISI 304 stainless steel, using a sub-resonant torsion pendulum (f congruent to 1 Hz) and a vibrant-reed instrument (f congruent to 10(3) Hz). Some experiments showed several internal friction peaks, which are attributed to dislocation relaxation and to martensitic transformation from gamma to alpha'. The characterization was carried out with X-ray, AFM and SEM. Analysis of X-ray peaks indicates a residual deformation in the order of 0.0005-0.0009 for gamma-phase and 0.0006-0.00204 for alpha'-phase. Two methods are presented to determine the adhesion energy by IF in coated materials: for the first the enthalpy is determined by means of isochronal IF measurements, while for the second it is determined using isothermal measurements. These produce an image of damage caused by the bombardment on the substrate, especially of the residual defects. (C) 2007 Elsevier B.V. All rights reserved.