Study On Mechanical Properties Of TiN / Metal Matrix Composite System Improved By Cryogenic Treatment

TiN and DLC films are widely used in various fields due to the high hardness, low friction coefficient, chemical stability etc. Although super hard films have been studied and many products have been commercialized, it is difficult to obtain high hardness, high toughness, good adhesion and good comprehensive performance of films due to deficiencies of membrane preparation and modification technology.Cryogenic treatment is a technology in the low temperature of the controlled object environment (usually a-125～196℃). It is widely used in steel, cemented carbide noferrous metal ceramics and nylon. Studies have shown that material strength and its wear resistance have been increased by changing the material microstructure and resistance stress. However, despite the cryogenic treatment technology is a gradually mature and widely used technology, there is only little studies in cryogenic treatment to thin film materials. What kind of impaction can we get after cryogenic treatment or the mechanism applied in body materials is a problem worthy to be discussed.Films deposited in YW2cemented carbide,304stainless steel and w9high-speed steel by arc ion plating are treated by simple process. It is discovered that after cryogenic treatment, hardness, fracture toughness, adhesion and friction coefficient of TiN on YW2cemented carbide304stainless steel, w9high speed steel three metal changed obviously. And the mechanism of improving the effect of cryogenic treatment of mechanical properties of TiN/matrix composite systems were discussed.It is shown that:(1)Fracture toughness of YW2cemented carbide and interface bonding strength of TiN/YW2system are improved after cryogenic treatment. It is found that gamma phase significantly reduced or disappeared, the porosity decreases, the organization became more compact by the observation of microstructure analysis.(2)After cryogenic treatment, the bonding strength of TiN films on stainless steel substrate has been improved and the hardness increases. This is because after cryogenic treatment, the TiN thin film structure tends to be dense, the thin film stress increase. In addition, the orientation of the film (111) plane after cryogenic treatment become obviously.(3)The hardness and wear resistance of High speed steel increased significantly after cryogenic treatment. This is due to the residual austenite transforms into martensite further, and precipitation of carbides in high speed steel particles in the organization, The surface stress change the friction performance. In the high-speed steel adhesion of TiN film is further improved, this is due to plastic deformation coordination of film and matrix ability and the result of the pinning effect of carbide. after cryogenic treatment (4)It seemed that friction curve of TiN/YW2keeps stable before and after treatment. Friction coefficient increased after cryogenic treatment. Wear resistance of YW2improved. Friction curve of TiN/304keeps unstable before and after treatment. Friction coefficient of TiN/304reduced after treatment. The friction coefficient of304steel reduced too. To the TiN/w9,friction coefficient of steel and film increased either. The friction curve became stable obviously after treatment.