Friction Wear And Liguid Impact Resistance Research Of Nano-Composite Carbon Nitride Coatings

In the field of materials engineering, the coatings technology is one important branch of material improvement. The hard coatings were widely used in materials protection from 70s 20th century, especially in prolong the life of metal cutting tools. The TiN is the first hard coatings material been widely used. The new hard materials like TiC TiB cubic BN TiCN and TiAIN were discovered to meet different using. The coatings were divided into two part according to there hardness:(l) hard coatings: Hv<40GPa,(2)superhard coatings: Hv>0GPa. The superhard coatings were divided into: essence like Diamond (HV=70- 100 GPa,), cubic BN(HV=48 GPa) and other B-N-C compounds; extension, like heterogeneity(super-lattice). The research of superhard material include the synthesize of materials whose hardness is near or exceed the hardness of Diamond and the technical method.There only a few superhard materials in nature, like cubic BN, amorphous carbon and diamond. They are thermodynamics unstable and are restricted to use in the cutting of iron and steel. The superhard materials based on superlattice and nano composite were developed during last decades.In 1989, Liu and Cohen predicted the ideal structure of B- C3N4 may has the hardness near or exceed the hardness of diamond based on empiristic formula of solid elastic modulus. This material is very good in chemical and thermal stability. The elastic modulus of B- C3N4 is B=410-440GPa calculated by Cohen and Liu based on ab-initial theory. There exist 7 kinds structure of C3N4 calculated by Liu , Cohen and Teter: two kinds of B- C3N4, two kinds of c-C3N4 and two graphite like structure.The superlattice coatings are an alternate multilayer structure under nanometer scale. The period thickness is 5-10 nanometer. In 1970 Koehler pointed out that the superlattice made up by two large different modulus materials may has high hardness based on dislocation theory. Late, the experiments showed this effect occurred in metal/metal superlattice. The experiments show that the single crystal nitride/nitride superlattices are superhard materials.One way to improve the anti-fracture of the coatings is deposition two different property films alternating. The model created by Koehler predicted that alternating deposition two high-low shear modulus materials would create new high yield strength materials. This kind of multilayer structure could prevent the expender of cracks. Under the same load, the internal bending stress in the multilayers is lower than that in the single layers. The alternating layers structure could give a shear stain area, the hard and brittle film is not easy break under frictionThis thesis presents investigation on the structure and physical properties, friction and wear properties, liquid impact resistance of carbon nitride films, carbon nitride/titanium nitride(CNx/TiN) nano-composite coatings prepared by magnetron sputtering, multi-arc medium frequency reactive unbalanced magnetron sputtering. The applications of CNx/TiN nano-composite coatings on cutting tools were also studied.C3N4 films were deposited on single crystal silicon substrate by magnetron sputtering. X-ray diffraction (XRD) showed there existed a, B phases of carbon nitride, and the 6 phase is the main phase. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) showed the ratio of N/C closed to the 1.06 and 1.24, and the C atoms were present in the form of sp and sp3 hybridization. The main bond mode is C-N bond.A self-made multi-arc medium frequency reactive unbalanced magnetron sputtering system was used to deposit CNx/TiN nano-composite coatings on high speed steel (HSS) substrates and HSS cutting tools. X-ray photoelectron spectroscopy (XPS) showed the content of N is 17-40%. X-ray diffraction (XRD) showed there existed the (111) textured TiN phase, atomic force microscope (AFM) and scanning electron microscope (SEM) showed the multi-arc medium frequency reactive unbalanced magnetron sputtering decreased the grain size of CNx/TiN, increase the surface...