Fabrication And Surface Properties Of Stainless Steel Films Deposited On TC4 Alloy By Magnetron Sputtering

Titanium alloys are excellent structural materials with high strength-to-weight, modular ratio and corrosion resistance. They have been widely used in aerospace, electronic industry, chemical engineering and so on. However, surface properties of titanium alloys such as tribological properties and oxidation resistance are always poor which restricts the extensive applications. More and more attentions have been paid on the surface modification of titanium alloys.In this work, DC magnetron sputtering was applied to deposit the stainless steel films on Ti6Al4V alloys to improve their surface properties. The orthogonal experiments were carried out to determine the optimal processing. Furthermore, the effect of the target current and bias voltage on the fabrication and surface properties of stainless steel films was focused on. Morphology, phase structures, wear resistance, micro-hardness, critical load and corrosion resistance of deposited films were systematically investigated by scanning electronic microscope (SEM), X-ray diffraction (XRD), ball-on-disk tribometer, Vickers indenter, scratch tester and electrochemistry tester respectively. The oxidation resistances of films were evaluated by measuring the rate of mass loss of the samples, after immersed in hydrogen peroxide with the concentration of 30% for ten days.The orthogonal experimental of results indicate that the target current and bias voltage are critical parameters which determine the surface properties of the stainless steel films such as wear and friction, critical load, corrosion and oxidation resistance.XRD results show that the phase structure of thin film is mainlyα-phase. Dense films are deposited with low current of magnetron target, and the film thickness of stainless steel increases with the target current increasing. The grain is smaller with higher bias voltage while there exists an optimal bias voltage to lead to highest depositions rate.The tribological property and hardness of Ti6Al4V alloy have been improved by coating a layer of stainless steel, which increase firstly and decrease afterwards with the target current or bias voltage increasing. The scratch test results indicate that the adhesion strength between the film and the substrate varies similarly as the hardness and tribological property of Ti6Al4V alloy.The oxidation resistance of the Ti6Al4V alloy has been enhanced obviously coated with a layer of stainless steel, which attributes to the fine grains grown at higher bias voltage or lower target current. The fine grains might lead to many diffusion paths in the film, through which Cr atoms could diffuse onto the surface and be oxidized to improve the oxidation resistance. While the corrosion resistance of stainless steel is slightly depressed comparing with Ti6Al4V alloy, and changes consistently with hardness and tribological property when the target current or bias voltage increased.