Production of Tin Films by Ion Beam Mixing Method and Clarification of Its Fatigue Fracture

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The ceramic thin films produced by ion beam technology, can modify the mechanical, optical, electronic and chemical properties. In the present study, two ion beam technologies were used to obtain the TiN films and CrN films. Such ceramic thin films were coated onto 600 MPa grade high tensile strength steel with varying the structure, compostion and film thickness. In dynamic mixing method, the ratio of Ti to N in the film can be changed by the deposition condition. When the ratio value of film is 1 : 1, there is the greatest hardness among the several thin films. The hardness decreases with increasing volume fraction of Ti. Furthermore, the structures of TiNx films depend on the mixture of TiN and Ti_2N and show more fine structure when the volume fraction of TiN increases. In this case, the hardness of film increases with increasing the volume fraction of TiN.The fatigue behavior depends on the coating thin film. When the TiN film is produced onto the steel, the fatigue life enlarges. Such a fatigue behavior results from the fatigue crack initiation process. Coating the film delays the crack initiation. The retardation of crack initiation markedly depends on the film structure and hardness. When the film structure is fine and its hardness is great, the fatigue life is strongly enhanced by the film deposition. Then, the fatigue life increases with laminating the thin film. The compressive residual stress into the film arise from the lamination of film, and then the film structure becomes more fine.