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

The evolution of the preferential orientation of TIN coatings deposite d on martensitic steel with the evaporation ion plating method is stud ied with the Field-Merchant X-ray diffraction technique for different coating thicknesses and as a function of the energy dissipation per un it 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) lattic e planes of most crystallites preferentially parallel with the substra te surface. The quantification of the evolution of the preferential or ientation is based on the mosaic spread of the preferential orientatio n factor p(111)(psi)-curve around psi = 0 degrees. The mosaic spread o f 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 fr om 1.0 +/- 0.4 MJ cm(-3) to 2.8 +/- 1.1 MJ cm(-3). The mosaic spread o f the (111) fibre texture decreases from 15 +/- 1 degrees to 8 +/- 1 d egrees 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, progressivel y with increasing layer thickness, and that evolution is more pronounc ed for a higher energy dissipation per unit volume in the growing laye r.