Microstructure and Tribological Properties of Ti(C,N)/a-C Gradient Composite Films

摘要

Ti(C, N)/a-C composite films with Ti-containing a-C layer deposited on multilayer Ti(C, N) layer, prepared by sputtering of graphite and titanium targets with closed-field unbalanced magnetron sputtering, have been characterized and measured with X-ray diffraction, transmission electron microscopy, microhardness tester and pin-on-disk tester. Results show that the bottom layers of the composite film exhibit multilayer structure consisting of fine nanocolumnar Ti(C, N) grains and the top layers of the film consist of 2-7 nm TiC nanocrystallites embedded in an amorphous C matrix. As increase of rotation speeds of the substrate, a transition from a multilayer nano-grain to a columnar-grain microstructure has been observed in the Ti(C, N) layer, and smaller and more uniform TiC nanocrystallites are also produced in the a-C layer. The Ti(C, N)/a-C gradient composite films exhibit high microhardness values (~40 Gpa) mostly coming from the bottom Ti(C, N) layer and simultaneously exhibit low friction coefficient (-0.15) coming from the top a-C layer. When wear occurring, the high microhardness of Ti(C, N) layer combining the low friction coefficient of a-C layer has increased the load capacity and wear resistance of the films, and give satisfactory friction performance in the pin-on-disk tests with a wear rate of 3.7×10-17 m3/m.N.