EXPERIMENTAL-STUDY OF THE GROWTH EVOLUTION FROM RANDOM TOWARDS A (111) PREFERENTIAL ORIENTATION OF PVD TIN COATINGS

Abstract

The evolution of the preferential orientation of TIN coatings deposited on martensitic steel with the evaporation ion plating method is studied with the Field-Merchant X-ray diffraction technique for different coating thicknesses and as a function of the energy dissipation per unit volume, S-E, in the growing layer. It was shown that TiN starts to grow on the martensitic substrates with randomly oriented grains, and that the texture evolves towards a fibre texture with the (111) lattice planes of most crystallites preferentially parallel with the substrate surface. The quantification of the evolution of the preferential orientation is based on the mosaic spread of the preferential orientation factor p(111)(psi)-curve around psi = 0 degrees. The mosaic spread of the (111) fibre texture decreases from 34 +/- 1 degrees to 10 +/- 1 degrees for an approximately 1.5 mu m thick coating as S, increases from 1.0 +/- 0.4 MJ cm(-3) to 2.8 +/- 1.1 MJ cm(-3). The mosaic spread of the (111) fibre texture decreases from 15 +/- 1 degrees to 8 +/- 1 degrees as the coating thickness changes from 0.9 mu m to 2.9 mu m for S-E = 2.5 +/- 1.0 MJ cm(-3). It is thus clearly demonstrated that the texture evolves from random towards a pure (111) texture, progressively with increasing layer thickness, and that evolution is more pronounced for a higher energy dissipation per unit volume in the growing layer.