Effect of Silicon Content on the Microstructure and Mechanical Properties of TiAlSiN Coatings Prepared by Reactive Magnetron Sputtering

Abstract

Titanium Aluminum Silicon Nitride (TiAlSiN) coating has been expected to be applied in the field of cutting new difficult- to-machine materials such as titanium and superalloys. TiAlSiN coatings in the range of 4-8 at.% silicon content are prepared by reactive magnetron sputtering. The results show that the structure of nanocrystal surrounded by amorphous Si3N4 was formed in all the TiAlSiN coatings. When the silicon content increases to 8 at.%, the grain size of TiAlSiN coatings is refined to 7 nm and distributes in a narrow size range. Meanwhile, the nano-column growth of the TiAlSiN coating with 4 at.% silicon disappeared and changed to nanocrystals growth. The hardness as a function of the silicon content showed a nonlinear relationship, and the highest hardness is obtained at 6 at.% silicon content. TiAlSiN coating with 4 at.% silicon content has the highest critical load of 87.8 N. With increasing silicon content, the preferred orientations change from (111) to (200) and the adhesion strength decreased. The optimized mechanical properties of the TiAlSiN coatings, with a hardness of about 32.8 GPa and a critical load of 69.2 N, will have a promising application in modern cutting technology.