Study On Fabrication And Characterization Of Superhard Ti-based Multi-element Nitride Coatings

In this thesis, we have investigated a series of Ti-based hardcoatings prepared by cathode arc vapor ion-plating method, such as TiN, TiAl(V)N, AlTiN and TiAl(Si)N, also attempted to fabricate (Ti,Al)N coatings with high Al content. These coatings have been characterized by the state-of-the-art techniques of XRD, nano-indentation, scratch test, SEM, RBS, etc. As the result, it was found that TiN coatings prepared by -100V DC bias are characterized with the (111) preferred orientation and the coatings prepared by pulsed bias with (111),(200) and (220) hybrid orientations. There are no any effect on the phase-structures of TiN coatings when adding Al and V elements with low concentration, however the lattice parameters of the coatings decrease and the hardness of the coatings increases. The lattice parameters of (Ti,Al)N coatings fabricated by TiAl alloy targets with 1 : 1 atoms ratio increase with the increase of duty cycle and bias, the maximum hardness of HV3000 was obtained on WC substrate under 40% and -150V, then decreased gradually with the change of them. The Al content examined by RBS showed only 30at.% in the coatings, obviously deviate from the targets', one of the most possible reasons was that the inhomogeneous dispersion of the Ti, Al powder in the targets favorable to produced more droplets of Al and the density of the Al ions in the plasma decreased, which resulted in the lower Al content in the coatings. The maximum hardness was obtained at the range of 50-60at.% Al concentration with the pure Al cathode arc target, which accompanied with the conversion of the structure from cubic NaCl to hexagonal wurtzite, the doping of little Si elements in the coatings was considered to play the role of delaying phase transformation. Al target was very seriously poisoned when we tried to fabricated high Al content (Ti,Al)N coatings by the ABS method, it was found that the increase of the density of sputter ion and Ar partial pressure was advantaged to the sputtering of the target, the poisoning mechanism of the target is discussed in this thesis with the Depla's theory.