Structure and properties of TiCN thin films prepared by graphite target and titanium target co-sputtering
TiCN thin films were prepared on M2 high-speed steel substrate by sputtering graphite target and titanium target in a mixed atmosphere of nitrogen and argon.The microstructure and structure of TiCN thin film were analyzed by scanning electron microscope and X-ray diffractometer. The hardness of TiCN thin film was tested by nano indentation instrument. Meanwhile, the combination of TiCN thin film and matrix was evaluated by indentation method and scratch method.The results show that the C atoms in TiCN thin film exist in the form of solid solution in TiN lattice, the orientation of TiCN thin film on (111) crystal surface is obviously weaker than that of TiN thin film, the fracture of TiCN thin film is a long block structure, its transverse size is smaller than that of TiN thin film, and the surface of TiCN thin film is concave and convex. The binding force between TiCN thin film and matrix is about 40N, and C atom has the effect of solid solution strengthening and fine crystal strengthening in TiCN thin film. The hardness of TiCN thin film increases from 20.3 of TiN film to 33.4GPa. TiCN film has good antifriction performance, and the service life of TiCN film taps is significantly improved when tapping 40Cr material than TiN film taps and uncoated taps.
The rapid development of modern cutting technology has put forward higher requirements for the material and properties of cutting tools. One of the feasible ways to improve tool performance is to deposit hard film on tool surface.TiN, TiC, TiCN and TiAlN hard film is the early appearance of several tool surface protection layer, is still widely used in the field of mechanical protection film. TiCN thin films are widely used in cutting tools, molds and wear resistant parts due to their high hardness and low friction coefficient.TiCN thin films are mainly prepared by vapor deposition, including chemical vapor deposition (CVD) and physical vapor deposition (PVD). CVD process of thin film prepared by the furnace temperature above 850 ℃, usually even medium temperature chemical vapor deposition technique (MT - CVD), its working temperature is about 600 ℃, the general beyond the steel mould and parts of the tempering temperature, so the method is not suitable for coating on the steel substrate. PVD of thin film prepared by the working temperature below 500 ℃, can satisfy the requirement of the steel substrate coating.
At present, most of the PVD methods use CH4 or C2H2 as the C source to prepare TiCN thin films. During the preparation process, TiCN thin films with different element content ratios and different properties can be obtained by adjusting the gas flow ratio.However, the problem with this method is that excessive carbon source gas will cause serious pollution to the internal structure of the coating machine furnace body, and the residual carbon loose layer in the furnace wall will be released in the next coating, interfering with the deposition atmosphere of the film, which is not conducive to continuous production, and often leads to the unstable performance of the film workpiece in industrial production.
Using solid C source to prepare TiCN film can greatly reduce or avoid the pollution of furnace body. Reactive magnetron sputtering is one of the main technologies of PVD method. The coating surface prepared by this method does not have large particle phenomenon, but has good surface quality, and can be used to prepare TiCN thin films on steel matrix.Guojun Zhang et al. prepared TiCN films under the mixed atmosphere of nitrogen and argon by sputtering graphite target and titanium target. They indicated that with the increase of sputtering power and deposition efficiency of graphite target, the total thickness and modulation cycle of the films obtained within the same time increased.With the increase of sputtering target power, the structure of TiCN thin film changed, and the crystal plane orientation (111) and (220) gradually weakened. The hardness of TiCN thin film first increased and then decreased, and the high hardness of z* reached more than 40GPa.The friction coefficient of TiCN thin film decreased with the increase of sputtering power of graphite target, and z* remained around 0.2.Xu junhua et al. prepared TiCN thin films with solid carbon source by magnetron sputtering technology. The influence of graphite sputtering target power obtained in this study on the structure and hardness of TiCN thin films was basically consistent with that of graphite sputtering current.However, the vacuum technology network (http://www.chvacuum.com/) believes that none of the above research reports have detected the composition of TiCN thin films. It is not clear about the carbon content in TiCN thin films prepared by using solid carbon sources, and the bonding strength between TiCN thin films and matrix has not been analyzed.
This paper USES the research and development of sichuan university RZP - 800 medium frequency reactive magnetron sputtering coating machine, using graphite target as carbon source, instead of CH4 or C2H2, in a mixture of nitrogen and argon atmosphere through preparation TiCN film sputtering of graphite target and titanium target, and the preparation method to acquire the TiCN film composition, structure, hardness and bonding strength are analyzed and the research, at the same time is investigated by the method in practical application of deposition TiCN film on the surface of high speed steel tap.
1. Experimental methods
1.1 materials and film preparation technology
Selection of M2 high speed steel as substrate material, the sample size is 6 mm x 10 mm x 6 mm, and prepare the same fabric Φ 10 mm spec tap number, used for cutting test.Sputtering targets were one pair of titanium target (purity 99.99%) and one pair of graphite target (purity 99.99%), and the two targets (4 targets) were arranged alternately and uniformly on the coating wall.Before coating, the surface of the sample was polished to remove macroscopic scratches visible to the naked eye and polished to the mirror surface. Then, the tap and the sample were sandblasted together to remove the pollution in the superficial layer. After ultrasonic cleaning, the sample was blow-dried and loaded into the furnace.Vacuum to 9.0 10-3 Pa, preheat the workpiece for 60min, and then use the effect of argon ion bombardment to etch and clean the substrate for 30min under negative bias.In order to improve the bonding strength between the film and the matrix, Ti metal blocks in the evaporative crucible deposit a layer of Ti metal transition layer on the matrix.After z*, at a pressure of 4.5 10-1 Pa, sputtered graphite target and titanium target were used to prepare TiCN thin films for 3h.The coating was cooled for 1h, and the samples were taken out.
1.2 structure and performance characterization of thin films
The fracture structure and surface morphology of TiCN thin film were observed by s-4800 (Hitachi, Japan) SEM, and the element content of the film was analyzed by EDS.X 'Pert Pro (Philips, Holland)X - ray diffraction (XRD) was used to analyze the phase composition and grain size of the coating.Nano Indenter XP test system (Agilent, America) was used to analyze the hardness and elastic modulus of the coating.Meanwhile, indentation method and scratch method were used to evaluate the bonding strength between the film and the matrix. Hr-150a rockwell hardness tester was used for indentation method, and the load was 150kg.The scratch method adopts hh-3000 scratch tester, and the load is 100N.The Z5135 vertical drilling machine was used for cutting test of the tap. The spindle speed of the drilling machine was 530r/min, the tapping material was 40Cr quenched and tempered steel, and the hardness of quenched and tempered was HRC29 ~ 32.
2, the conclusion
Using solid carbon source, the graphite target and titanium target were co-sputtered by reactive magnetron sputtering technology to prepare TiCN thin films on high-speed steel substrate. The structure and properties of the obtained TiCN thin films were systematically analyzed, and the conclusions were as follows:
(1) the fracture of TiCN thin film presented a long block structure growing perpendicular to the interface. The concavo-convex structure on the surface of TiCN thin film was weaker than that of TiN thin film, while there were more microparticles on the surface of TiCN thin film. TiCN thin film forms a solid solution based on TiN. The addition of C atom significantly reduces the diffraction peak of the thin film on the (111) crystal surface.
(2) due to the solid solution strengthening and fine crystal strengthening of C atom, the hardness of TiCN film was significantly improved compared with TiN film, and the hardness of TiCN film was 33.4GPa. After the Ti transition layer was used as the substrate, the bonding strength between TiCN film and TiN film and M2 high-speed steel substrate was not significantly different, both of which were about 40N.
(3) the wear form of TiCN film is mainly abrasive wear, which forms a carbon transfer film on the surface of the film during friction and wear. The film plays a role of solid lubrication and anti-friction. The service life of TiCN film taps is significantly improved when tapping 40Cr material, which is 3 times higher than that of non-film taps and 1.6 times higher than that of TiN film taps, respectively.
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