| Currently, hard coatings are important for cutting tools, surface modification, as barrier materials for modern industrial application. Among them titanium nitride is the most popular first generation cutting tool coating. However, to meet further stringent requirements of machining technology, the coatings have been put on a development direction from binary coating to multiple, multilayered, and nanocomposite coatings. Combined with the typical example of binary?polybasic and nano-superlattices coatings, we do give the detail comparation of different films. Above that, the article also introduce the most acceptable theory of thin films growing, the most common apparatus for fabricating the superhard coatings, This dissertation focuses on the synthesis, analysis, and industrial applications of TiBN-based nanocomposite coatings, and systematical research is carried out from three perspectives.(1) TiBN/TiN multilayered coating with different modulation periods (bilayer thickness) have been synthesized using typical cathodic arc plasma deposition equipment. The objective of this work is to study the influence of modulation period on the microstructure, mechanical and tribological properties. TiBN/TiN multilayer coatings exhibited a TiN (111), (200), (220) and TiB2 (220) crystallographic orientations and preferred TiN (111) orientation. With the decrease of modulation period from 12 nm to 1.9 nm, The microstructure of TiBN/TiN multilayered coating evolves form nanocrystalline TiN/a-BN to nanocomposite Ti(B,N) with an dense amorphous BN phase, The maximum values of hardness and elastic modulus reached 31.6 GPa and 336 GPa with a bilayer period of 1.9 nmSecondly, TiBN/CrN multilayered superlattice coatings with modulation periods A (bilayer thickness) ranging from 22.5 to 4.2 nm and modulation ratio R (the thickness ratio of CrN and TiBN layers) ranging from 6:1 to 3:1 were synthesized using an industrial-scale cathodic arc ion plating system in an Ar-N2 gas mixture. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindention were employed to investigate the influence of modulation period and ratio on microstructure and mechanical properties of the multilayers. The sharp interfaces and nanoscale multilayered modulation were confirmed by TEM. TiBN/CrN multilayer coatings were crystallized with orientations at the (111), (200) and (220) crystallographic planes and the microstructure was strengthened at (200) preferred orientation. The maximum hardness of 38.6 GPa and elastic modulus of 477 GPa were obtained at ?=11.7 nm and R=5:1. The lowest value of the friction coefficient at 0.32 sliding against a WC-Co ball was obtained at a bilayer period of 11.7 nm, compared to those of the coatings with other modulation periods and monolithic coatings. The wear rate of the multilayered coatings was also lower than those of the monolithic CrN and TiBN coatings.respectively.(2) Ti-B-N based coating systems show a promising potential in the field of non-ferrous metals machining. The TiBN nanocomposite coatings are multiphase of TiN, BN and TiB2. TiBCN nanocomposite coatings were deposited on cemented carbide and Si (100) substrates by a cathodic arc ion plating system using TiB2 cathode in N2 and C2H2 atmosphere. The structure, mechanical and tribological properties of the coatings are found to be highly dependent on the C2H2 flow rate, high resolution X-ray photoelectron spectroscopy (HRXPS) show that the coatings consist of crystalline phases Ti(B,C) and Ti(C,N) and amorphous phases BN, CNx, and carbon. Transmission electron microscopy shows 100-200 nm and 3-6 nm nanocrystals embedded in amorphous matrices when the C2H2 flow rate are 200 and 300 seem, respectively. XPS shows characteristic bonding of Ti(B,C), TiN, Ti(C,N), and BN after etching. The hardness of the coatings decreases from 24.65 GPa to 19.24 GPa with increasing C2H2 flow rate from 0-300 seem. Ball-on-disk tests show that the friction coefficients decreases from 0.84 to 0.128 and the adhesive force increases from 7 N to 38.7 N with increasing C2H2 flow rate from 0-300 seem.(3) Finally, Nanocomposite TiSiBN thin film have been synthesized on cemented carbide and Si substrate by cathodic arc plasma deposition from TiB2 compound target with various N2/SiH4 mixtures. TiSiBN coatings were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation and ball-on-disk wear tests. The influence of nitrogen pressure on the structure and mechanical properties of the coatings were investigated. The thickness of the film was of the order of 4?m. The Ti-Si-B-N coatings consisting of 8-20nm nanocrystaline TiN (nc-TiN) and hexagonal TiB2 (h-TiB2) compounds changed from a nano-columnar to a nanocomposite structure. The coatings with a nitrogen content of less than 8 at.% exhibited superhardness values in the range of 41-45 GPa, but also showed poor adhesion and low wear resistance. High values of hardness of these coatings were due to the high density of boundaries between the small, nanometer size grains embedded in the matrix of amorphous TiSiBN phases. With a further increase in the N content in the coatings to levels greater than 36 at.%, the inter-particle spacing of the nanocrystalline compounds increased significantly led to low hardness and poor wear resistance, respectively.(4) The intrinsic hardness of nano coating material reflects the material's ability to fight elastic-plastic deformation;Not only with material of temperament hardness within the atom structure is also associated with the characteristics of microstructure and crystal orientation of material;This article attempts to from the perspective of thermodynamics and crystal dislocation accumulation for theoretical interpretation of the superhard coating... |
PDF Full Text Request