High Strength and Wear Resistance of Tantalum by Ultrasonic Nanocrystalline Surface Modification Technique at High Temperatures

Enhancing the strength of materials is of great concern in that the failures such as wear, corrosion and fatigue occur on the surface. A tantalum (Ta), which is a refractory metal, was subjected to severe plastic deformation induced by ultrasonic nanocrystalline surface modification (UNSM) technique at room- and high-temperatures of 200°C and 800°C. The mechanical properties and wear resistance of Ta before and after UNSM treatment were characterized by X-ray diffraction (XRD), hardness tester, and ball-on-disk tribometer, respectively. The UNSM treatment at 800°C led to the intensity reduction and broadening, and the diffraction peaks were shifted to lower angles, which means the presence of compressive residual stress and grain size refinement. The hardness of the UNSM-treated sample at room temperature was higher than that of the untreated one, and it was further increased with increasing the UNSM treatment temperature. In addition, the effect of UNSM treatment at high-temperature on wear resistance was significant than that of the UNSM treatment at room-temperature. We demonstrate the possibility of further increasing the mechanical properties and wear resistance of Ta by UNSM treatment at high-temperatures in comparison with the untreated and UNSM-treatment at room temperature, which would be beneficial for applications of Ta. (paper)