Wear and Corrosion Resistance of Surface Plasma Tantalum Modified Layer on Pure Copper

This paper aims to improve the wear resistance and corrosion resistance of pure copper by plasma Ta coating. The Ta coating was engineered onto the surface of pure copper by double glow plasma surface alloying technology. The microstructure, elements distribution and phase identification of the Ta coating were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Subsequently, the nano-hardness and adhesion strength were measured by nano-indentation tester and scratch tester. The tribological property and anticorrosion property of the Ta coating were carried out by using reciprocating friction and wear tester and electrochemical workstation at room temperature, respectively. The results showed that the Ta coating exhibited a compact and homogeneous structure, with the thicknesses of about 12 μm and the matrix 3 μm interdiffusion transition layer, and the main phase of the coating was α-Ta. The interfacial bond strength between the coating and the substrate was excellent, and the critical load for the coating delamination was 25.8 N. The nano-hardness of the Ta coating was improved from 1.5 GPa to 7.0 GPa. As compared with pure copper substrate, the friction coefficient of the Ta coating declines from 1.15 to 0.82, and the specific wear rate decreased from 46.97×10−5 mm3/(N·m) to 22.91×10−5 mm3/(N·m). Pure copper wore very badly, and there were many grooves and ridges paralleled to the sliding direction with some randomly distributed particles. On the other hand, the wear track of Ta coating was smaller and narrower and most area of the wear track was smooth. The wear resistance of the Ta coating was improved significantly due to its high hardness, which limited plastic deformation of the wear surface. The wear mechanism of the substrate was adhesive wear, while wear mechanism of the Ta coating was slight abrasive wear. The self-corrosion potential and polarization resistance of the Ta coating were significantly increased, and the self-corrosion current density was decreased. The Ta coating hindered the diffusion of Cl‒ in solution to pure copper matrix, and weakened the electrochemical corrosion of the material. Meanwhile, the corrosion potential of the Ta coating was higher than that of pure copper matrix, which improved the thermodynamic stability of the material and exhibits better corrosion resistance in 3.5wt.% NaCl solution. It is concluded that the Ta coating can effectively improve the wear resistance and corrosion resistance of pure copper. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.