Laser surface alloying of copper with Cr/Ti/CNT for enhancing surface properties
Yi Yang, Valentino A.M. Cristino, Lap Mou Tam, Kin Ho Lo, C.T. Kwok
Abstract
In this study, laser surface alloying of commercially pure copper (cp Cu) with Cr/Ti and Cr/Ti/CNT was conducted using a high-power diode laser. Cu–Ti intermetallic phases were detected in the Cu/Cr matrix of the laser-alloyed specimens without CNT. While TiC was found in the Cu/Cr matrix of the laser-alloyed layers with CNT. Compared to cp Cu (60 ± 10 HV0.2), the laser-alloyed specimens without and with CNT could achieve hardness up to 423 ± 12 HV0.2 and 860 ± 24 HV0.2 respectively. Sliding wear tests were also carried out at 60 km/h in dry condition with a pin-on-disc tribometer. Compared with cp Cu, the wear resistances of all laser-alloyed specimens were significantly improved due to solid solution alloying, existence of harder phases including Cr, Cu–Ti intermetallics and TiC. The wear resistance of the laser-alloyed specimens was increased up to a factor of 1220 times as compared with cp Cu. For the polarization study, the corrosion current densities of all laser-alloyed specimens (0.164–0.275 μA/cm2) in 3.5% NaCl solution at 25 °C were found to be lower than that of copper (3.362 μA/cm2) due to presence of passive Cr and Ti.