Microstructure and Mechanical Properties of Nitrogen Flux Alternating AlTiN Composite Multilayer Coatings

摘要

The AlTiN composition multilayer coatings were deposited on high speed steel substrates with a medium-frequency (MF) reactive magnetron sputtering system using TiAl targets. During deposition of AlTiN multilayer coatings nitrogen flux was alternated in different periods. X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure of AlTiN composition multilayer coatings. Their mechanical behaviors and adhesion properties were investigated using nano-indenter and scratch test. The result indicated that the presently deposited multilayer thin films consisted of alternating AlTiN with different nitrogen contents in different layer thicknesses. In each layer, AlTiN exhibited nanocomposites of nanocrystallites embedded into amorphous matrices despite of their nitrogen content. The difference between adjacent layers is that AlTiN layer with lower nitrogen content has a lower density of nanocrystallites. Formation of multilayer structure greatly increased the critical load at which film-substrate interface delamination occurs and adhesion energy although it only slightly increased both hardness and elastic modulus values, which indicates that formation of multilayer structure is beneficial for improvement of adhesion. Increase of nitrogen flux enhanced this effect.