Effect of fluxes on wettability between the molten Galfan alloy and Q235 steel matrix

Effect of fluxes on wettability between the molten Galfan alloy and steel matrix was studied by modified sessile drop method. Five fluxes were selected and numbered as Z1-(ZnCl2, NH4Cl), Z2-(ZnCl2, NaF), Z3-(ZnCl2, NaCl, CaCl2, SnCl2, CeCl3), Z4-(ZnCl2, NH4Cl, KCl, BiCl3), Z5-(ZnCl2, NH4Cl, SnCl2, KF). Results show that some components in fluxes react with zinc oxide and alumina on the alloy surface, thus reducing the interfacial energy and improving wettability between molten alloy and steel matrix. Initial contact angles between molten alloy and steel matrix decrease from 122.3° to 99.7°, and the interfacial energy (σsl) decreases from 0.92σG J/m2 to 0.79σG J/m2 when the flux varies from Z1 to Z5. The wettability of Z5 flux was the best, which shortened the incubation period before the interface reaction due to its rapid decomposition and volatilization. The main chemical factors determining wettability of each flux are Z1-NH4Cl, Z2-NaF, Z3-CaCl2 and SnCl2, Z4-NH4Cl and BiCl3, Z5-KF, SnCl2 and NH4Cl respectively.