Spray forming and wear characteristics of liquid immiscible alloys

Alloys based on Al–Pb and Cu–Pb systems were gas atomized and spray deposited over a copper substrate. Microstructural examination of Cu–20Pb alloy indicated an equiaxed grain morphology of the primary α-phase with dispersion of Pb particles along the grain boundary and inter-granular regions. A wide size rage of atomised powder particles of this alloy showed cellular-dendritic morphology of the primary α-phase. The microstructure of spray formed Al–4Cu–20Pb alloy revealed a uniform distribution of ultrafine Pb particles in Al-matrix in contrast to a bimodal size distribution of Pb particles in atomised powder particles. Microstructural homogeneity was observed in both the atomized powders and spray formed alloys. The wear rate of Cu–20Pb alloy was observed to be higher than that of Al–4Cu–20Pb alloy at low load and sliding velocity. However, the former indicated a low wear rate in severe wear regime of high load and sliding velocity. The mode of solidification of liquid immiscible alloys during spray forming process is discussed and the wear behaviour of these alloys is analysed in light of their microstructural features.