Ti/TiN Multilayer Coatings on Titanium Alloys

Titanium alloys have been widely used in manufacturing of fans, compressor disks, and blades of advanced aircraft engines. However, titanium alloys are very sensitive to fretting fatigue damage, which may affect the safe reliability of the aircraft engine compressor. The multilayer coatings seem to be the most promising coating concept due to many requirements (e.g. multifunctional character, moderate residual stresses, good adherence to metallic substrates, proper hardness to toughness ratio and low friction coefficients) for titanium alloys exposed to complex wear conditions. This work aims the development of techniques for production of Ti/TiN multilayer coatings by Electron Beam Physical Vapor Deposition (EB-PVD) in order to define the influence of the number and thickness of the layers in the surface hardness of Ti-13Nb-13Zr alloy produced by powder metallurgy (P/M) from elemental hydrides. The samples were characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Vickers indentation. The multilayers presented a continuous and columnar structure, large thickness and high adhesion to the substrates. It was possible to establish a relation involving the number and the thickness of the layers with the final surface hardness.