Nanocomposites nc-TiN/a-Si3N4/a- and nc-TiSi2 with hardness exceeding 100 GPa and high fracture toughness

In course of further development of our generic concept for the design of novel superhard nanocomposites [1,2] we have recently developed new multi-phase ultrahard nanocomposite coatings with Vickers mirohardness of 80 to 105 GPa which is in the range of natural diamond. The coatings show a high elastic recovery of up to 90% upon a relatively large indentation deformation The hardness measured by the depth sensing technique agree with those calculated from the area of the remaining pseudoplastic deformation. The very high apparent fracture toughness is illustrated by the absence of any radial cracks upon indentation with a large load of 1 N into 10.3 mu m thick film [3]. The unusual combination of high hardness, elastic recovery and apparent fracture toughness was attributed to the ample possibility of cracks deflection, meandering and termination during loading and cracks closure upon unloading [1,2,4]. The suggested nanostructure of the coatings has been elucidated on a basis of a complex analysis by means XRD, EDX, ERD, XPS and HR TEM.