Investigation Of The Microstructures And Properties Of CrTiAlN Coatings Doped Carbon

In this paper, CrTiAlCN coatings with various carbon contents were prepared by reaction magnetron sputtering technology with graphite target as the C supplier. The phases, constituent and the microstructure of the deposited coatings were characterized and analyzed by using X-ray diffraction, scan electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The microhardnesses and adhesion strengths of the deposited coatings were measured by a digital microhardness tester and the wear resistance properties were evaluated by pin-on-disc test. The results show that with the increasing C target current, C content of CrTiAlCN film increases, also, the deposited CrTiAlCN film microstructures convert from columnar structure to nanocomposite microstructure that nano-particle embedded in the amorphous matrix. Furthermore, coatings show typical multilayer structure with periodical thickness of about lOnm when the current of C target is 3A. The C target current effects on the phase and structure evolution of the multilayer coatings significantly, the preferred growth orientation of principal CrN phase change from (111) to (200), especially, TiC phase is observed with graphite target current of 3A. With increasing C target current, file structure convert from fine nano-columnar microstructure to nanocomposite microstructure of nano-particle embedded in an amorphous matrix, at the same time, the grains are refined evidently and spacing of sp2C-C C-rich layer decreases.The CrTiAlCN coatings have high hardness (in present study, the hardness is measured as 2500～2850Hv), as well as good adhesion strength, above properties are determined by grain size and exist of C-rich layers. Nano-scaled multilayer structure of coatings not only enhances the hardness but also improves the adhesion strength due to the stress can be relaxed effectively under load. These superior properties and composite structure of the CrTiAlCN coatings lead to the excellent wear resistance. With increasing C target current, friction coefficient of CrTiAlCN decreases, however, the weight loss rate is at the same level with CrTiAIN film.