Overspray injection in spray forming of CuSn13.5 billets

In the conventional spray forming process the yield, i.e. the ratio of the deposited material mass to the atomized melt mass, ranges from 50 to 80%. The feedback of overspray to the process by means of injection into the spray cone has several promising advantages, including increase of the overall yield, decrease of gas consumption, and reduction of segregation. However, overall porosity increases. Several CuSn13.5 billets were spray-formed with varied Powder to Melt mass flow Ratio (PMR) of 0, 0.1, 0.2 and 0.3, varied Gas to Melt mass flow Ratio (GMR) of 0.7 to 0.56 and varied particle sizes of the injected overspray powders (different sieving fractions from 0 to 300 μm). Analyses of the microstructure, porosity, radial segregation of Sn, and the yield were carried out and correlated with the process parameters.