Microstructure and properties of mixed Cu-Sn and Fe-based alloys without or with molybdenum addition processed by plasma transferred arc

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 M7C3 phases, as the precipitating alloy particles were distributed on the Cu-rich matrix that consisted of α(Cu, Sn) and Cu41Sn11 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.