Search

Abstract: This paper proposes a new available palladium-free surface activation process on polycarbonate (PC) engineering plastic before electroless plating. Surface morphologies of the original plastic, activated plastic, surface and cross-sections after electroless plating were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersion spectrometry (EDS) and X-ray diffraction (XRD). The growth mechanism of copper layers was discussed. Results show that numerous folds, uneven steps, and other defects appear on the microscopic surface of activated plastic. After direct electroless plating, the plating layer on the plastic surface exhibits a closely bound granular distribution. Compared with the conventional pretreatment process, the plating layer possesses a similar morphology. The growth mechanisms are analyzed as follows: the reactant (Cu2+) in the electroless plating solution disperses and is adsorbed by the plastic surface in the process of Cu plating. The Cu particles that settled form the nucleus and grow. The growth process involves repeated gathering of nano-level Cu grains to form physically agglomerated Cu granules. The Cu grains finally merge to allow closely bound and evenly distributed copper plating. [Copyright &y& Elsevier]

In this study, two types of powders were processed by plasma transferred arc (PTA) to form coatings. In the first case, Cu–Sn powder and Fe-based powder were mixed at a weight ratio of 85:15 (Cu–Sn/Fe-based). In the second case, the Cu–Sn/Fe-based powder was blended with Mo powder at a weight ratio of 96:4 (Cu–Sn/Fe-based/Mo). Therefore, the weight ratio among Cu–Sn, Fe-based, and Mo powders was 81.6:14.4:4 in the second type powders. Liquid phase separation occurred in the Cu–Sn/Fe-based and Cu–Sn/Fe-based/Mo coatings. The Fe-rich spheroids comprised γ(Fe, Ni) and M 7 C 3 phases, as the precipitating alloy particles were distributed on the Cu-rich matrix that consisted of α(Cu, Sn) and Cu 41 Sn 11 phases. The relative content of the Fe-rich spheroids in the Cu–Sn/Fe-based/Mo coating exceeded that in the Cu–Sn/Fe-based coating. The number of Fe-rich spheroids in the Cu–Sn/Fe-based coating increased far away from its substrate, and obvious macro-segregation could be seen close to its substrate. When Mo was further added, the numbers of Fe-rich spheroids were increased and obvious macro-segregation could not be easily found when compared to the Cu–Sn/Fe-based coating. The wear rate of the Cu–Sn/Fe-based and Cu–Sn/Fe-based/Mo coatings was lower than that of the Cu–Sn coating, and a distinct improvement on the wear rate could be obtained in the Cu–Su/Fe-based/Mo coating. The friction coefficient of the Cu–Sn/Fe-based/Mo coating exceeded that of the Cu–Sn coating but was lower than that of the Cu–Sn/Fe-based coating. The pitting corrosion resistance of the Cu–Sn/Fe-based and Cu–Sn/Fe-based/Mo coatings was higher than that of the Cu–Sn coating and the highest one could be obtained in the Cu–Sn/Fe-based/Mo coating. [ABSTRACT FROM AUTHOR]

In this study, two types of blended alloys were processed by plasma transferred arc (PTA) hardfacing to form coatings. In the first case, a pre-alloyed Cu-Sn alloy and a pre-alloyed Co-base alloy were blended at a weight ratio of 85:15 (Cu-Sn/Co-base). In the second case, the pre-alloyed Cu-Sn and Co-base alloys were mixed with the molybdenum (Mo) element at a weight ratio of 81:15:4 (Cu-Sn/Co-base/Mo). Metastable liquid phase separation formed in the Cu-Sn/Co-base and Cu-Sn/Co-base/Mo coatings. The Co-rich spheroids as the minor precipitating alloy particles distributed on the Cu-rich matrix. The Co-rich spheroids consisted of α(Co) and M 7 C 3 phases, and the Cu-rich matrix included α(Cu, Sn) and Cu 10 Sn 3 phases. The relative content of α(Co) + M 7 C 3 phases in the Cu-Sn/Co-base/Mo coating was higher than that in the Cu-Sn/Co-base coating. The numbers of the Co-rich spheroids in the cross section of the Cu-Sn/Co-base coating increased with increasing the distance from the substrate, and an obvious macroscopic segregation could be found in the coating close to its substrate. When Mo as additive was further added, the numbers of the Co-rich spheroids in the cross section of the coating increased and the macroscopic segregation could not be seen when compared to that in the Cu-Sn/Co-base coating. The wear rate of the Cu-Sn/Co-base and Cu-Sn/Co-base/Mo coatings was lower than that of the Cu-Sn coating, and a distinct improvement of the wear rate could be obtained in the Cu-Su/Co-base/Mo coating, attributing to mainly the increasing hardness of the coatings by sequence of the Cu-Sn coating, Cu-Sn/Co-base coating, and Cu-Sn/Co-base/Mo coating. The friction coefficient of the coatings has an increasing trend by sequence of the Cu-Sn coating, Cu-Sn/Co-base coating, and Cu-Sn/Co-base/Mo coating, but an obvious difference could not be seen in the coatings. [ABSTRACT FROM AUTHOR]