Study On The Preparation And Uniformity Of Ti Films Deposited On The Surface Of The Hemispherical Workpiece

Vacuum sputtering coating is an important method to improve the surface performance of parts and prolong their service life.However,for the complex shaped workpieces,such as head cover,cams,moulds,and so on,because there are different angles between different parts of workpiece surface and target material,the shadow effect of oblique incidence will be produced in the film deposition,thus causing the difference of thickness,structure and properties of the deposited film in different parts.In the service process of the workpiece,once the thin film at the weakest point of performance has failed,the entire workpiece can no longer be used normally.Therefore,it is important to systematically grasp the uniformity of film deposition rate,structure,and performance in different parts of complex-shaped workpiece surface,and optimize the process for specific purposes.This has important engineering significance for improving the overall service life of components.In this paper,hemispherical workpiece,a representative 3D solid workpiece,is used as a model workpiece,and metal titanium film as the representative film.Firstly,the uniformity of thin films deposited on the inner and outer surfaces of hemispherical workpieces by two methods of direct current magnetron sputtering and high power pulsed magnetron sputtering was studied.The results showed that the structural and performance uniformity of the HPPMS deposited film is better than that of the film deposited by the DCMS method.On this basis,the influence of process parameters in the HPPMS method on the uniformity of the deposited film was further studied,and the influence of the substrate bias voltage on the uniformity of the film deposition rate,thin film structure and performance was studied emphatically.Before film deposition,7 pieces of silicon wafer(20*10mm)were mounted on the inner and outer surface of the hemispherical workpiece along the same longitude with equal distance.The deposition rate,phase structure,microhardness and cross sectional morphology of Ti films deposited on these silicon wafers were characterized by step instrument,XRD,ultra-microhardness tester and SEM respectively,on this basis,the uniformity of the film deposited on the inner and outer surface of the workpiece was analyzed.The results are as follows:(1)When the film was prepared by DCMS,for the inner surface of the hemispherical workpiece,the deposition rate increased with the increase of the inclination angle of the hemispherical workpiece,the distribution of "edge thick bottom thin" was generally presented on the surface of hemispherical workpiece(Note:sample tilt angle refers to the angle between the normal direction of the sample location and the direction of the target normal line,where the hemispherical workpiece bottom is 0 degrees,and the workpiece edge is 90 degrees);Film hardness decreased dramatically with the increase of the tilt angle of the sample;The crystal structure of the thin film had obvious preferential orientation difference from the edge to the bottom.For the outer surface of the hemispherical workpiece,thin film deposition rate decreased as sample tilt angle increased,thin film crystal structure also changed with the sample angle and film hardness decreased with increasing sample tilt.When the film was prepared by HPPMS,in both the inner and outer surfaces of the hemispherical workpiece,the film deposition rate and hardness decreased as the sample tilt angle increased,for the inner surface of the hemispherical workpiece,the crystal structure of the thin film was uniform,but the film crystal structure of the outer surface of the hemispherical workpiece changed with the change of angle.In general,the homogeneity of the film was significantly better than the DCMS method in the preparation of thin films in HPPMS(2)When the film was prepared by HPPMS,for the inner surface of the hemispherical workpiece,the film deposition rate on the inner surface of the hemispherical workpiece was reduced with the increase of substrate bias voltage and film hardness increased,however,the difference of film deposition rate,crystal structure and hardness was reduced at different positions,and the uniformity was improved.(3)For the outer surface of the hemispherical workpiece,the increase of the substrate bias voltage could effectively improve the uniformity of the hardness distribution of the deposited film,but had little effect on the distribution and uniformity of the film deposition rate.With the increase of substrate bias voltage,the crystal structure orientation of the film surface varied at different positions on the outer surface of the workpiece.The results of this paper have important reference value for understanding the uniformity distribution and uniformity optimization of the inner and outer surface deposition films of hemispherical workpiece.