Study On Characterization And Improvement Of Mechanical Properties Of Carbon Films

With the purpose of improving the mechanical property of rigid carbon film, on the basis of the coating concept of Metal containing DLC (Me-DLC) film, silver-containing diamond-like carbon films (Ag-DLC) and copper containing diamond-like carbon films (Cu-DLC) with different metal contents were deposited. Diamond films, in the micron scale, were deposited on the SiC transition layer by chemical vapor deposition. In this paper, we explore the characterization method of the mechanical property of rigid carbon film by researching the improvement of rigid carbon film, and then obtained its mechanism. Conclusions are as follows:(1) The characterization of thin film toughness was explored from both energy and stress aspect, the combination of the impact toughness and scratch toughness of the film can be a complete reflection of the toughness of the film. The toughening of thin films is the result of the interaction of the five mechanisms:(Ⅰ) The compressive stress, generated by appropriate ion bombardment during the preparation of films; (Ⅱ) The new "atomic cluster" formed by doping became smaller resulting in the increase of grain boundary and grain boundary slip, and the stress concentration factor decreases; (Ⅲ) The "ligament" effect on the yield and toughness of the ductile phase; (IV) The decrease of mutual exclusion of homogeneous carbon atoms; (Ⅴ) The shearing soft metal, relieving stress field. Compared with the experimental results, the mechanism of Ⅱ, Ⅲ and V plays a leading role.(2) The characterization methods of the mechanical properties of diamond films with micron order of magnitude are explored. The Natural diamond indenter was replaced by artificial diamond indenter due to its go high bearing capacity in the vertical direction. The elastic modulus and hardness of the diamond film can be calculated by the corrected indentation depth and the indentation area which related to indenter geometries. We can qualitatively evaluate the relative size of a series of films by obverting the displacement steps on the loading curve under heavy load.(3) The adhesion properties of diamond films was improved by preparing silicon carbide transition layer on the surface of cemented carbide tool. The bonding property of diamond film and substrate is related to the mechanical properties of the film itself. Orthogonal experiment results show that the bias is the main parameter that affects the adhesion properties of diamond films, and the optimal combination of SiC transition layer:bias 100V, target current 10A, acetylene gas flow rate 45sccm. We could infer the binding force enhancement mechanism by observing surface morphology and Raman spectra of the samples deposited at different temperatures.